| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * linux/fs/namei.c |
| * |
| * Copyright (C) 1991, 1992 Linus Torvalds |
| */ |
| |
| /* |
| * Some corrections by tytso. |
| */ |
| |
| /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname |
| * lookup logic. |
| */ |
| /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture. |
| */ |
| |
| #include <linux/init.h> |
| #include <linux/export.h> |
| #include <linux/kernel.h> |
| #include <linux/slab.h> |
| #include <linux/fs.h> |
| #include <linux/namei.h> |
| #include <linux/pagemap.h> |
| #include <linux/sched/mm.h> |
| #include <linux/fsnotify.h> |
| #include <linux/personality.h> |
| #include <linux/security.h> |
| #include <linux/ima.h> |
| #include <linux/syscalls.h> |
| #include <linux/mount.h> |
| #include <linux/audit.h> |
| #include <linux/capability.h> |
| #include <linux/file.h> |
| #include <linux/fcntl.h> |
| #include <linux/device_cgroup.h> |
| #include <linux/fs_struct.h> |
| #include <linux/posix_acl.h> |
| #include <linux/hash.h> |
| #include <linux/bitops.h> |
| #include <linux/init_task.h> |
| #include <linux/uaccess.h> |
| |
| #include "internal.h" |
| #include "mount.h" |
| |
| /* [Feb-1997 T. Schoebel-Theuer] |
| * Fundamental changes in the pathname lookup mechanisms (namei) |
| * were necessary because of omirr. The reason is that omirr needs |
| * to know the _real_ pathname, not the user-supplied one, in case |
| * of symlinks (and also when transname replacements occur). |
| * |
| * The new code replaces the old recursive symlink resolution with |
| * an iterative one (in case of non-nested symlink chains). It does |
| * this with calls to <fs>_follow_link(). |
| * As a side effect, dir_namei(), _namei() and follow_link() are now |
| * replaced with a single function lookup_dentry() that can handle all |
| * the special cases of the former code. |
| * |
| * With the new dcache, the pathname is stored at each inode, at least as |
| * long as the refcount of the inode is positive. As a side effect, the |
| * size of the dcache depends on the inode cache and thus is dynamic. |
| * |
| * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink |
| * resolution to correspond with current state of the code. |
| * |
| * Note that the symlink resolution is not *completely* iterative. |
| * There is still a significant amount of tail- and mid- recursion in |
| * the algorithm. Also, note that <fs>_readlink() is not used in |
| * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink() |
| * may return different results than <fs>_follow_link(). Many virtual |
| * filesystems (including /proc) exhibit this behavior. |
| */ |
| |
| /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation: |
| * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL |
| * and the name already exists in form of a symlink, try to create the new |
| * name indicated by the symlink. The old code always complained that the |
| * name already exists, due to not following the symlink even if its target |
| * is nonexistent. The new semantics affects also mknod() and link() when |
| * the name is a symlink pointing to a non-existent name. |
| * |
| * I don't know which semantics is the right one, since I have no access |
| * to standards. But I found by trial that HP-UX 9.0 has the full "new" |
| * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the |
| * "old" one. Personally, I think the new semantics is much more logical. |
| * Note that "ln old new" where "new" is a symlink pointing to a non-existing |
| * file does succeed in both HP-UX and SunOs, but not in Solaris |
| * and in the old Linux semantics. |
| */ |
| |
| /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink |
| * semantics. See the comments in "open_namei" and "do_link" below. |
| * |
| * [10-Sep-98 Alan Modra] Another symlink change. |
| */ |
| |
| /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks: |
| * inside the path - always follow. |
| * in the last component in creation/removal/renaming - never follow. |
| * if LOOKUP_FOLLOW passed - follow. |
| * if the pathname has trailing slashes - follow. |
| * otherwise - don't follow. |
| * (applied in that order). |
| * |
| * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT |
| * restored for 2.4. This is the last surviving part of old 4.2BSD bug. |
| * During the 2.4 we need to fix the userland stuff depending on it - |
| * hopefully we will be able to get rid of that wart in 2.5. So far only |
| * XEmacs seems to be relying on it... |
| */ |
| /* |
| * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland) |
| * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives |
| * any extra contention... |
| */ |
| |
| /* In order to reduce some races, while at the same time doing additional |
| * checking and hopefully speeding things up, we copy filenames to the |
| * kernel data space before using them.. |
| * |
| * POSIX.1 2.4: an empty pathname is invalid (ENOENT). |
| * PATH_MAX includes the nul terminator --RR. |
| */ |
| |
| #define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname)) |
| |
| struct filename * |
| getname_flags(const char __user *filename, int flags, int *empty) |
| { |
| struct filename *result; |
| char *kname; |
| int len; |
| |
| result = audit_reusename(filename); |
| if (result) |
| return result; |
| |
| result = __getname(); |
| if (unlikely(!result)) |
| return ERR_PTR(-ENOMEM); |
| |
| /* |
| * First, try to embed the struct filename inside the names_cache |
| * allocation |
| */ |
| kname = (char *)result->iname; |
| result->name = kname; |
| |
| len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX); |
| if (unlikely(len < 0)) { |
| __putname(result); |
| return ERR_PTR(len); |
| } |
| |
| /* |
| * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a |
| * separate struct filename so we can dedicate the entire |
| * names_cache allocation for the pathname, and re-do the copy from |
| * userland. |
| */ |
| if (unlikely(len == EMBEDDED_NAME_MAX)) { |
| const size_t size = offsetof(struct filename, iname[1]); |
| kname = (char *)result; |
| |
| /* |
| * size is chosen that way we to guarantee that |
| * result->iname[0] is within the same object and that |
| * kname can't be equal to result->iname, no matter what. |
| */ |
| result = kzalloc(size, GFP_KERNEL); |
| if (unlikely(!result)) { |
| __putname(kname); |
| return ERR_PTR(-ENOMEM); |
| } |
| result->name = kname; |
| len = strncpy_from_user(kname, filename, PATH_MAX); |
| if (unlikely(len < 0)) { |
| __putname(kname); |
| kfree(result); |
| return ERR_PTR(len); |
| } |
| if (unlikely(len == PATH_MAX)) { |
| __putname(kname); |
| kfree(result); |
| return ERR_PTR(-ENAMETOOLONG); |
| } |
| } |
| |
| result->refcnt = 1; |
| /* The empty path is special. */ |
| if (unlikely(!len)) { |
| if (empty) |
| *empty = 1; |
| if (!(flags & LOOKUP_EMPTY)) { |
| putname(result); |
| return ERR_PTR(-ENOENT); |
| } |
| } |
| |
| result->uptr = filename; |
| result->aname = NULL; |
| audit_getname(result); |
| return result; |
| } |
| |
| struct filename * |
| getname_uflags(const char __user *filename, int uflags) |
| { |
| int flags = (uflags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0; |
| |
| return getname_flags(filename, flags, NULL); |
| } |
| |
| struct filename * |
| getname(const char __user * filename) |
| { |
| return getname_flags(filename, 0, NULL); |
| } |
| |
| struct filename * |
| getname_kernel(const char * filename) |
| { |
| struct filename *result; |
| int len = strlen(filename) + 1; |
| |
| result = __getname(); |
| if (unlikely(!result)) |
| return ERR_PTR(-ENOMEM); |
| |
| if (len <= EMBEDDED_NAME_MAX) { |
| result->name = (char *)result->iname; |
| } else if (len <= PATH_MAX) { |
| const size_t size = offsetof(struct filename, iname[1]); |
| struct filename *tmp; |
| |
| tmp = kmalloc(size, GFP_KERNEL); |
| if (unlikely(!tmp)) { |
| __putname(result); |
| return ERR_PTR(-ENOMEM); |
| } |
| tmp->name = (char *)result; |
| result = tmp; |
| } else { |
| __putname(result); |
| return ERR_PTR(-ENAMETOOLONG); |
| } |
| memcpy((char *)result->name, filename, len); |
| result->uptr = NULL; |
| result->aname = NULL; |
| result->refcnt = 1; |
| audit_getname(result); |
| |
| return result; |
| } |
| EXPORT_SYMBOL(getname_kernel); |
| |
| void putname(struct filename *name) |
| { |
| if (IS_ERR(name)) |
| return; |
| |
| BUG_ON(name->refcnt <= 0); |
| |
| if (--name->refcnt > 0) |
| return; |
| |
| if (name->name != name->iname) { |
| __putname(name->name); |
| kfree(name); |
| } else |
| __putname(name); |
| } |
| EXPORT_SYMBOL(putname); |
| |
| /** |
| * check_acl - perform ACL permission checking |
| * @mnt_userns: user namespace of the mount the inode was found from |
| * @inode: inode to check permissions on |
| * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...) |
| * |
| * This function performs the ACL permission checking. Since this function |
| * retrieve POSIX acls it needs to know whether it is called from a blocking or |
| * non-blocking context and thus cares about the MAY_NOT_BLOCK bit. |
| * |
| * If the inode has been found through an idmapped mount the user namespace of |
| * the vfsmount must be passed through @mnt_userns. This function will then take |
| * care to map the inode according to @mnt_userns before checking permissions. |
| * On non-idmapped mounts or if permission checking is to be performed on the |
| * raw inode simply passs init_user_ns. |
| */ |
| static int check_acl(struct user_namespace *mnt_userns, |
| struct inode *inode, int mask) |
| { |
| #ifdef CONFIG_FS_POSIX_ACL |
| struct posix_acl *acl; |
| |
| if (mask & MAY_NOT_BLOCK) { |
| acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS); |
| if (!acl) |
| return -EAGAIN; |
| /* no ->get_acl() calls in RCU mode... */ |
| if (is_uncached_acl(acl)) |
| return -ECHILD; |
| return posix_acl_permission(mnt_userns, inode, acl, mask); |
| } |
| |
| acl = get_acl(inode, ACL_TYPE_ACCESS); |
| if (IS_ERR(acl)) |
| return PTR_ERR(acl); |
| if (acl) { |
| int error = posix_acl_permission(mnt_userns, inode, acl, mask); |
| posix_acl_release(acl); |
| return error; |
| } |
| #endif |
| |
| return -EAGAIN; |
| } |
| |
| /** |
| * acl_permission_check - perform basic UNIX permission checking |
| * @mnt_userns: user namespace of the mount the inode was found from |
| * @inode: inode to check permissions on |
| * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...) |
| * |
| * This function performs the basic UNIX permission checking. Since this |
| * function may retrieve POSIX acls it needs to know whether it is called from a |
| * blocking or non-blocking context and thus cares about the MAY_NOT_BLOCK bit. |
| * |
| * If the inode has been found through an idmapped mount the user namespace of |
| * the vfsmount must be passed through @mnt_userns. This function will then take |
| * care to map the inode according to @mnt_userns before checking permissions. |
| * On non-idmapped mounts or if permission checking is to be performed on the |
| * raw inode simply passs init_user_ns. |
| */ |
| static int acl_permission_check(struct user_namespace *mnt_userns, |
| struct inode *inode, int mask) |
| { |
| unsigned int mode = inode->i_mode; |
| kuid_t i_uid; |
| |
| /* Are we the owner? If so, ACL's don't matter */ |
| i_uid = i_uid_into_mnt(mnt_userns, inode); |
| if (likely(uid_eq(current_fsuid(), i_uid))) { |
| mask &= 7; |
| mode >>= 6; |
| return (mask & ~mode) ? -EACCES : 0; |
| } |
| |
| /* Do we have ACL's? */ |
| if (IS_POSIXACL(inode) && (mode & S_IRWXG)) { |
| int error = check_acl(mnt_userns, inode, mask); |
| if (error != -EAGAIN) |
| return error; |
| } |
| |
| /* Only RWX matters for group/other mode bits */ |
| mask &= 7; |
| |
| /* |
| * Are the group permissions different from |
| * the other permissions in the bits we care |
| * about? Need to check group ownership if so. |
| */ |
| if (mask & (mode ^ (mode >> 3))) { |
| kgid_t kgid = i_gid_into_mnt(mnt_userns, inode); |
| if (in_group_p(kgid)) |
| mode >>= 3; |
| } |
| |
| /* Bits in 'mode' clear that we require? */ |
| return (mask & ~mode) ? -EACCES : 0; |
| } |
| |
| /** |
| * generic_permission - check for access rights on a Posix-like filesystem |
| * @mnt_userns: user namespace of the mount the inode was found from |
| * @inode: inode to check access rights for |
| * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, |
| * %MAY_NOT_BLOCK ...) |
| * |
| * Used to check for read/write/execute permissions on a file. |
| * We use "fsuid" for this, letting us set arbitrary permissions |
| * for filesystem access without changing the "normal" uids which |
| * are used for other things. |
| * |
| * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk |
| * request cannot be satisfied (eg. requires blocking or too much complexity). |
| * It would then be called again in ref-walk mode. |
| * |
| * If the inode has been found through an idmapped mount the user namespace of |
| * the vfsmount must be passed through @mnt_userns. This function will then take |
| * care to map the inode according to @mnt_userns before checking permissions. |
| * On non-idmapped mounts or if permission checking is to be performed on the |
| * raw inode simply passs init_user_ns. |
| */ |
| int generic_permission(struct user_namespace *mnt_userns, struct inode *inode, |
| int mask) |
| { |
| int ret; |
| |
| /* |
| * Do the basic permission checks. |
| */ |
| ret = acl_permission_check(mnt_userns, inode, mask); |
| if (ret != -EACCES) |
| return ret; |
| |
| if (S_ISDIR(inode->i_mode)) { |
| /* DACs are overridable for directories */ |
| if (!(mask & MAY_WRITE)) |
| if (capable_wrt_inode_uidgid(mnt_userns, inode, |
| CAP_DAC_READ_SEARCH)) |
| return 0; |
| if (capable_wrt_inode_uidgid(mnt_userns, inode, |
| CAP_DAC_OVERRIDE)) |
| return 0; |
| return -EACCES; |
| } |
| |
| /* |
| * Searching includes executable on directories, else just read. |
| */ |
| mask &= MAY_READ | MAY_WRITE | MAY_EXEC; |
| if (mask == MAY_READ) |
| if (capable_wrt_inode_uidgid(mnt_userns, inode, |
| CAP_DAC_READ_SEARCH)) |
| return 0; |
| /* |
| * Read/write DACs are always overridable. |
| * Executable DACs are overridable when there is |
| * at least one exec bit set. |
| */ |
| if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO)) |
| if (capable_wrt_inode_uidgid(mnt_userns, inode, |
| CAP_DAC_OVERRIDE)) |
| return 0; |
| |
| return -EACCES; |
| } |
| EXPORT_SYMBOL(generic_permission); |
| |
| /** |
| * do_inode_permission - UNIX permission checking |
| * @mnt_userns: user namespace of the mount the inode was found from |
| * @inode: inode to check permissions on |
| * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...) |
| * |
| * We _really_ want to just do "generic_permission()" without |
| * even looking at the inode->i_op values. So we keep a cache |
| * flag in inode->i_opflags, that says "this has not special |
| * permission function, use the fast case". |
| */ |
| static inline int do_inode_permission(struct user_namespace *mnt_userns, |
| struct inode *inode, int mask) |
| { |
| if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) { |
| if (likely(inode->i_op->permission)) |
| return inode->i_op->permission(mnt_userns, inode, mask); |
| |
| /* This gets set once for the inode lifetime */ |
| spin_lock(&inode->i_lock); |
| inode->i_opflags |= IOP_FASTPERM; |
| spin_unlock(&inode->i_lock); |
| } |
| return generic_permission(mnt_userns, inode, mask); |
| } |
| |
| /** |
| * sb_permission - Check superblock-level permissions |
| * @sb: Superblock of inode to check permission on |
| * @inode: Inode to check permission on |
| * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) |
| * |
| * Separate out file-system wide checks from inode-specific permission checks. |
| */ |
| static int sb_permission(struct super_block *sb, struct inode *inode, int mask) |
| { |
| if (unlikely(mask & MAY_WRITE)) { |
| umode_t mode = inode->i_mode; |
| |
| /* Nobody gets write access to a read-only fs. */ |
| if (sb_rdonly(sb) && (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) |
| return -EROFS; |
| } |
| return 0; |
| } |
| |
| /** |
| * inode_permission - Check for access rights to a given inode |
| * @mnt_userns: User namespace of the mount the inode was found from |
| * @inode: Inode to check permission on |
| * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) |
| * |
| * Check for read/write/execute permissions on an inode. We use fs[ug]id for |
| * this, letting us set arbitrary permissions for filesystem access without |
| * changing the "normal" UIDs which are used for other things. |
| * |
| * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. |
| */ |
| int inode_permission(struct user_namespace *mnt_userns, |
| struct inode *inode, int mask) |
| { |
| int retval; |
| |
| retval = sb_permission(inode->i_sb, inode, mask); |
| if (retval) |
| return retval; |
| |
| if (unlikely(mask & MAY_WRITE)) { |
| /* |
| * Nobody gets write access to an immutable file. |
| */ |
| if (IS_IMMUTABLE(inode)) |
| return -EPERM; |
| |
| /* |
| * Updating mtime will likely cause i_uid and i_gid to be |
| * written back improperly if their true value is unknown |
| * to the vfs. |
| */ |
| if (HAS_UNMAPPED_ID(mnt_userns, inode)) |
| return -EACCES; |
| } |
| |
| retval = do_inode_permission(mnt_userns, inode, mask); |
| if (retval) |
| return retval; |
| |
| retval = devcgroup_inode_permission(inode, mask); |
| if (retval) |
| return retval; |
| |
| return security_inode_permission(inode, mask); |
| } |
| EXPORT_SYMBOL(inode_permission); |
| |
| /** |
| * path_get - get a reference to a path |
| * @path: path to get the reference to |
| * |
| * Given a path increment the reference count to the dentry and the vfsmount. |
| */ |
| void path_get(const struct path *path) |
| { |
| mntget(path->mnt); |
| dget(path->dentry); |
| } |
| EXPORT_SYMBOL(path_get); |
| |
| /** |
| * path_put - put a reference to a path |
| * @path: path to put the reference to |
| * |
| * Given a path decrement the reference count to the dentry and the vfsmount. |
| */ |
| void path_put(const struct path *path) |
| { |
| dput(path->dentry); |
| mntput(path->mnt); |
| } |
| EXPORT_SYMBOL(path_put); |
| |
| #define EMBEDDED_LEVELS 2 |
| struct nameidata { |
| struct path path; |
| struct qstr last; |
| struct path root; |
| struct inode *inode; /* path.dentry.d_inode */ |
| unsigned int flags, state; |
| unsigned seq, next_seq, m_seq, r_seq; |
| int last_type; |
| unsigned depth; |
| int total_link_count; |
| struct saved { |
| struct path link; |
| struct delayed_call done; |
| const char *name; |
| unsigned seq; |
| } *stack, internal[EMBEDDED_LEVELS]; |
| struct filename *name; |
| struct nameidata *saved; |
| unsigned root_seq; |
| int dfd; |
| kuid_t dir_uid; |
| umode_t dir_mode; |
| } __randomize_layout; |
| |
| #define ND_ROOT_PRESET 1 |
| #define ND_ROOT_GRABBED 2 |
| #define ND_JUMPED 4 |
| |
| static void __set_nameidata(struct nameidata *p, int dfd, struct filename *name) |
| { |
| struct nameidata *old = current->nameidata; |
| p->stack = p->internal; |
| p->depth = 0; |
| p->dfd = dfd; |
| p->name = name; |
| p->path.mnt = NULL; |
| p->path.dentry = NULL; |
| p->total_link_count = old ? old->total_link_count : 0; |
| p->saved = old; |
| current->nameidata = p; |
| } |
| |
| static inline void set_nameidata(struct nameidata *p, int dfd, struct filename *name, |
| const struct path *root) |
| { |
| __set_nameidata(p, dfd, name); |
| p->state = 0; |
| if (unlikely(root)) { |
| p->state = ND_ROOT_PRESET; |
| p->root = *root; |
| } |
| } |
| |
| static void restore_nameidata(void) |
| { |
| struct nameidata *now = current->nameidata, *old = now->saved; |
| |
| current->nameidata = old; |
| if (old) |
| old->total_link_count = now->total_link_count; |
| if (now->stack != now->internal) |
| kfree(now->stack); |
| } |
| |
| static bool nd_alloc_stack(struct nameidata *nd) |
| { |
| struct saved *p; |
| |
| p= kmalloc_array(MAXSYMLINKS, sizeof(struct saved), |
| nd->flags & LOOKUP_RCU ? GFP_ATOMIC : GFP_KERNEL); |
| if (unlikely(!p)) |
| return false; |
| memcpy(p, nd->internal, sizeof(nd->internal)); |
| nd->stack = p; |
| return true; |
| } |
| |
| /** |
| * path_connected - Verify that a dentry is below mnt.mnt_root |
| * |
| * Rename can sometimes move a file or directory outside of a bind |
| * mount, path_connected allows those cases to be detected. |
| */ |
| static bool path_connected(struct vfsmount *mnt, struct dentry *dentry) |
| { |
| struct super_block *sb = mnt->mnt_sb; |
| |
| /* Bind mounts can have disconnected paths */ |
| if (mnt->mnt_root == sb->s_root) |
| return true; |
| |
| return is_subdir(dentry, mnt->mnt_root); |
| } |
| |
| static void drop_links(struct nameidata *nd) |
| { |
| int i = nd->depth; |
| while (i--) { |
| struct saved *last = nd->stack + i; |
| do_delayed_call(&last->done); |
| clear_delayed_call(&last->done); |
| } |
| } |
| |
| static void leave_rcu(struct nameidata *nd) |
| { |
| nd->flags &= ~LOOKUP_RCU; |
| nd->seq = nd->next_seq = 0; |
| rcu_read_unlock(); |
| } |
| |
| static void terminate_walk(struct nameidata *nd) |
| { |
| drop_links(nd); |
| if (!(nd->flags & LOOKUP_RCU)) { |
| int i; |
| path_put(&nd->path); |
| for (i = 0; i < nd->depth; i++) |
| path_put(&nd->stack[i].link); |
| if (nd->state & ND_ROOT_GRABBED) { |
| path_put(&nd->root); |
| nd->state &= ~ND_ROOT_GRABBED; |
| } |
| } else { |
| leave_rcu(nd); |
| } |
| nd->depth = 0; |
| nd->path.mnt = NULL; |
| nd->path.dentry = NULL; |
| } |
| |
| /* path_put is needed afterwards regardless of success or failure */ |
| static bool __legitimize_path(struct path *path, unsigned seq, unsigned mseq) |
| { |
| int res = __legitimize_mnt(path->mnt, mseq); |
| if (unlikely(res)) { |
| if (res > 0) |
| path->mnt = NULL; |
| path->dentry = NULL; |
| return false; |
| } |
| if (unlikely(!lockref_get_not_dead(&path->dentry->d_lockref))) { |
| path->dentry = NULL; |
| return false; |
| } |
| return !read_seqcount_retry(&path->dentry->d_seq, seq); |
| } |
| |
| static inline bool legitimize_path(struct nameidata *nd, |
| struct path *path, unsigned seq) |
| { |
| return __legitimize_path(path, seq, nd->m_seq); |
| } |
| |
| static bool legitimize_links(struct nameidata *nd) |
| { |
| int i; |
| if (unlikely(nd->flags & LOOKUP_CACHED)) { |
| drop_links(nd); |
| nd->depth = 0; |
| return false; |
| } |
| for (i = 0; i < nd->depth; i++) { |
| struct saved *last = nd->stack + i; |
| if (unlikely(!legitimize_path(nd, &last->link, last->seq))) { |
| drop_links(nd); |
| nd->depth = i + 1; |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| static bool legitimize_root(struct nameidata *nd) |
| { |
| /* Nothing to do if nd->root is zero or is managed by the VFS user. */ |
| if (!nd->root.mnt || (nd->state & ND_ROOT_PRESET)) |
| return true; |
| nd->state |= ND_ROOT_GRABBED; |
| return legitimize_path(nd, &nd->root, nd->root_seq); |
| } |
| |
| /* |
| * Path walking has 2 modes, rcu-walk and ref-walk (see |
| * Documentation/filesystems/path-lookup.txt). In situations when we can't |
| * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab |
| * normal reference counts on dentries and vfsmounts to transition to ref-walk |
| * mode. Refcounts are grabbed at the last known good point before rcu-walk |
| * got stuck, so ref-walk may continue from there. If this is not successful |
| * (eg. a seqcount has changed), then failure is returned and it's up to caller |
| * to restart the path walk from the beginning in ref-walk mode. |
| */ |
| |
| /** |
| * try_to_unlazy - try to switch to ref-walk mode. |
| * @nd: nameidata pathwalk data |
| * Returns: true on success, false on failure |
| * |
| * try_to_unlazy attempts to legitimize the current nd->path and nd->root |
| * for ref-walk mode. |
| * Must be called from rcu-walk context. |
| * Nothing should touch nameidata between try_to_unlazy() failure and |
| * terminate_walk(). |
| */ |
| static bool try_to_unlazy(struct nameidata *nd) |
| { |
| struct dentry *parent = nd->path.dentry; |
| |
| BUG_ON(!(nd->flags & LOOKUP_RCU)); |
| |
| if (unlikely(!legitimize_links(nd))) |
| goto out1; |
| if (unlikely(!legitimize_path(nd, &nd->path, nd->seq))) |
| goto out; |
| if (unlikely(!legitimize_root(nd))) |
| goto out; |
| leave_rcu(nd); |
| BUG_ON(nd->inode != parent->d_inode); |
| return true; |
| |
| out1: |
| nd->path.mnt = NULL; |
| nd->path.dentry = NULL; |
| out: |
| leave_rcu(nd); |
| return false; |
| } |
| |
| /** |
| * try_to_unlazy_next - try to switch to ref-walk mode. |
| * @nd: nameidata pathwalk data |
| * @dentry: next dentry to step into |
| * Returns: true on success, false on failure |
| * |
| * Similar to try_to_unlazy(), but here we have the next dentry already |
| * picked by rcu-walk and want to legitimize that in addition to the current |
| * nd->path and nd->root for ref-walk mode. Must be called from rcu-walk context. |
| * Nothing should touch nameidata between try_to_unlazy_next() failure and |
| * terminate_walk(). |
| */ |
| static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry) |
| { |
| int res; |
| BUG_ON(!(nd->flags & LOOKUP_RCU)); |
| |
| if (unlikely(!legitimize_links(nd))) |
| goto out2; |
| res = __legitimize_mnt(nd->path.mnt, nd->m_seq); |
| if (unlikely(res)) { |
| if (res > 0) |
| goto out2; |
| goto out1; |
| } |
| if (unlikely(!lockref_get_not_dead(&nd->path.dentry->d_lockref))) |
| goto out1; |
| |
| /* |
| * We need to move both the parent and the dentry from the RCU domain |
| * to be properly refcounted. And the sequence number in the dentry |
| * validates *both* dentry counters, since we checked the sequence |
| * number of the parent after we got the child sequence number. So we |
| * know the parent must still be valid if the child sequence number is |
| */ |
| if (unlikely(!lockref_get_not_dead(&dentry->d_lockref))) |
| goto out; |
| if (read_seqcount_retry(&dentry->d_seq, nd->next_seq)) |
| goto out_dput; |
| /* |
| * Sequence counts matched. Now make sure that the root is |
| * still valid and get it if required. |
| */ |
| if (unlikely(!legitimize_root(nd))) |
| goto out_dput; |
| leave_rcu(nd); |
| return true; |
| |
| out2: |
| nd->path.mnt = NULL; |
| out1: |
| nd->path.dentry = NULL; |
| out: |
| leave_rcu(nd); |
| return false; |
| out_dput: |
| leave_rcu(nd); |
| dput(dentry); |
| return false; |
| } |
| |
| static inline int d_revalidate(struct dentry *dentry, unsigned int flags) |
| { |
| if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) |
| return dentry->d_op->d_revalidate(dentry, flags); |
| else |
| return 1; |
| } |
| |
| /** |
| * complete_walk - successful completion of path walk |
| * @nd: pointer nameidata |
| * |
| * If we had been in RCU mode, drop out of it and legitimize nd->path. |
| * Revalidate the final result, unless we'd already done that during |
| * the path walk or the filesystem doesn't ask for it. Return 0 on |
| * success, -error on failure. In case of failure caller does not |
| * need to drop nd->path. |
| */ |
| static int complete_walk(struct nameidata *nd) |
| { |
| struct dentry *dentry = nd->path.dentry; |
| int status; |
| |
| if (nd->flags & LOOKUP_RCU) { |
| /* |
| * We don't want to zero nd->root for scoped-lookups or |
| * externally-managed nd->root. |
| */ |
| if (!(nd->state & ND_ROOT_PRESET)) |
| if (!(nd->flags & LOOKUP_IS_SCOPED)) |
| nd->root.mnt = NULL; |
| nd->flags &= ~LOOKUP_CACHED; |
| if (!try_to_unlazy(nd)) |
| return -ECHILD; |
| } |
| |
| if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) { |
| /* |
| * While the guarantee of LOOKUP_IS_SCOPED is (roughly) "don't |
| * ever step outside the root during lookup" and should already |
| * be guaranteed by the rest of namei, we want to avoid a namei |
| * BUG resulting in userspace being given a path that was not |
| * scoped within the root at some point during the lookup. |
| * |
| * So, do a final sanity-check to make sure that in the |
| * worst-case scenario (a complete bypass of LOOKUP_IS_SCOPED) |
| * we won't silently return an fd completely outside of the |
| * requested root to userspace. |
| * |
| * Userspace could move the path outside the root after this |
| * check, but as discussed elsewhere this is not a concern (the |
| * resolved file was inside the root at some point). |
| */ |
| if (!path_is_under(&nd->path, &nd->root)) |
| return -EXDEV; |
| } |
| |
| if (likely(!(nd->state & ND_JUMPED))) |
| return 0; |
| |
| if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE))) |
| return 0; |
| |
| status = dentry->d_op->d_weak_revalidate(dentry, nd->flags); |
| if (status > 0) |
| return 0; |
| |
| if (!status) |
| status = -ESTALE; |
| |
| return status; |
| } |
| |
| static int set_root(struct nameidata *nd) |
| { |
| struct fs_struct *fs = current->fs; |
| |
| /* |
| * Jumping to the real root in a scoped-lookup is a BUG in namei, but we |
| * still have to ensure it doesn't happen because it will cause a breakout |
| * from the dirfd. |
| */ |
| if (WARN_ON(nd->flags & LOOKUP_IS_SCOPED)) |
| return -ENOTRECOVERABLE; |
| |
| if (nd->flags & LOOKUP_RCU) { |
| unsigned seq; |
| |
| do { |
| seq = read_seqcount_begin(&fs->seq); |
| nd->root = fs->root; |
| nd->root_seq = __read_seqcount_begin(&nd->root.dentry->d_seq); |
| } while (read_seqcount_retry(&fs->seq, seq)); |
| } else { |
| get_fs_root(fs, &nd->root); |
| nd->state |= ND_ROOT_GRABBED; |
| } |
| return 0; |
| } |
| |
| static int nd_jump_root(struct nameidata *nd) |
| { |
| if (unlikely(nd->flags & LOOKUP_BENEATH)) |
| return -EXDEV; |
| if (unlikely(nd->flags & LOOKUP_NO_XDEV)) { |
| /* Absolute path arguments to path_init() are allowed. */ |
| if (nd->path.mnt != NULL && nd->path.mnt != nd->root.mnt) |
| return -EXDEV; |
| } |
| if (!nd->root.mnt) { |
| int error = set_root(nd); |
| if (error) |
| return error; |
| } |
| if (nd->flags & LOOKUP_RCU) { |
| struct dentry *d; |
| nd->path = nd->root; |
| d = nd->path.dentry; |
| nd->inode = d->d_inode; |
| nd->seq = nd->root_seq; |
| if (read_seqcount_retry(&d->d_seq, nd->seq)) |
| return -ECHILD; |
| } else { |
| path_put(&nd->path); |
| nd->path = nd->root; |
| path_get(&nd->path); |
| nd->inode = nd->path.dentry->d_inode; |
| } |
| nd->state |= ND_JUMPED; |
| return 0; |
| } |
| |
| /* |
| * Helper to directly jump to a known parsed path from ->get_link, |
| * caller must have taken a reference to path beforehand. |
| */ |
| int nd_jump_link(const struct path *path) |
| { |
| int error = -ELOOP; |
| struct nameidata *nd = current->nameidata; |
| |
| if (unlikely(nd->flags & LOOKUP_NO_MAGICLINKS)) |
| goto err; |
| |
| error = -EXDEV; |
| if (unlikely(nd->flags & LOOKUP_NO_XDEV)) { |
| if (nd->path.mnt != path->mnt) |
| goto err; |
| } |
| /* Not currently safe for scoped-lookups. */ |
| if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) |
| goto err; |
| |
| path_put(&nd->path); |
| nd->path = *path; |
| nd->inode = nd->path.dentry->d_inode; |
| nd->state |= ND_JUMPED; |
| return 0; |
| |
| err: |
| path_put(path); |
| return error; |
| } |
| |
| static inline void put_link(struct nameidata *nd) |
| { |
| struct saved *last = nd->stack + --nd->depth; |
| do_delayed_call(&last->done); |
| if (!(nd->flags & LOOKUP_RCU)) |
| path_put(&last->link); |
| } |
| |
| static int sysctl_protected_symlinks __read_mostly; |
| static int sysctl_protected_hardlinks __read_mostly; |
| static int sysctl_protected_fifos __read_mostly; |
| static int sysctl_protected_regular __read_mostly; |
| |
| #ifdef CONFIG_SYSCTL |
| static struct ctl_table namei_sysctls[] = { |
| { |
| .procname = "protected_symlinks", |
| .data = &sysctl_protected_symlinks, |
| .maxlen = sizeof(int), |
| .mode = 0644, |
| .proc_handler = proc_dointvec_minmax, |
| .extra1 = SYSCTL_ZERO, |
| .extra2 = SYSCTL_ONE, |
| }, |
| { |
| .procname = "protected_hardlinks", |
| .data = &sysctl_protected_hardlinks, |
| .maxlen = sizeof(int), |
| .mode = 0644, |
| .proc_handler = proc_dointvec_minmax, |
| .extra1 = SYSCTL_ZERO, |
| .extra2 = SYSCTL_ONE, |
| }, |
| { |
| .procname = "protected_fifos", |
| .data = &sysctl_protected_fifos, |
| .maxlen = sizeof(int), |
| .mode = 0644, |
| .proc_handler = proc_dointvec_minmax, |
| .extra1 = SYSCTL_ZERO, |
| .extra2 = SYSCTL_TWO, |
| }, |
| { |
| .procname = "protected_regular", |
| .data = &sysctl_protected_regular, |
| .maxlen = sizeof(int), |
| .mode = 0644, |
| .proc_handler = proc_dointvec_minmax, |
| .extra1 = SYSCTL_ZERO, |
| .extra2 = SYSCTL_TWO, |
| }, |
| { } |
| }; |
| |
| static int __init init_fs_namei_sysctls(void) |
| { |
| register_sysctl_init("fs", namei_sysctls); |
| return 0; |
| } |
| fs_initcall(init_fs_namei_sysctls); |
| |
| #endif /* CONFIG_SYSCTL */ |
| |
| /** |
| * may_follow_link - Check symlink following for unsafe situations |
| * @nd: nameidata pathwalk data |
| * |
| * In the case of the sysctl_protected_symlinks sysctl being enabled, |
| * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is |
| * in a sticky world-writable directory. This is to protect privileged |
| * processes from failing races against path names that may change out |
| * from under them by way of other users creating malicious symlinks. |
| * It will permit symlinks to be followed only when outside a sticky |
| * world-writable directory, or when the uid of the symlink and follower |
| * match, or when the directory owner matches the symlink's owner. |
| * |
| * Returns 0 if following the symlink is allowed, -ve on error. |
| */ |
| static inline int may_follow_link(struct nameidata *nd, const struct inode *inode) |
| { |
| struct user_namespace *mnt_userns; |
| kuid_t i_uid; |
| |
| if (!sysctl_protected_symlinks) |
| return 0; |
| |
| mnt_userns = mnt_user_ns(nd->path.mnt); |
| i_uid = i_uid_into_mnt(mnt_userns, inode); |
| /* Allowed if owner and follower match. */ |
| if (uid_eq(current_cred()->fsuid, i_uid)) |
| return 0; |
| |
| /* Allowed if parent directory not sticky and world-writable. */ |
| if ((nd->dir_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH)) |
| return 0; |
| |
| /* Allowed if parent directory and link owner match. */ |
| if (uid_valid(nd->dir_uid) && uid_eq(nd->dir_uid, i_uid)) |
| return 0; |
| |
| if (nd->flags & LOOKUP_RCU) |
| return -ECHILD; |
| |
| audit_inode(nd->name, nd->stack[0].link.dentry, 0); |
| audit_log_path_denied(AUDIT_ANOM_LINK, "follow_link"); |
| return -EACCES; |
| } |
| |
| /** |
| * safe_hardlink_source - Check for safe hardlink conditions |
| * @mnt_userns: user namespace of the mount the inode was found from |
| * @inode: the source inode to hardlink from |
| * |
| * Return false if at least one of the following conditions: |
| * - inode is not a regular file |
| * - inode is setuid |
| * - inode is setgid and group-exec |
| * - access failure for read and write |
| * |
| * Otherwise returns true. |
| */ |
| static bool safe_hardlink_source(struct user_namespace *mnt_userns, |
| struct inode *inode) |
| { |
| umode_t mode = inode->i_mode; |
| |
| /* Special files should not get pinned to the filesystem. */ |
| if (!S_ISREG(mode)) |
| return false; |
| |
| /* Setuid files should not get pinned to the filesystem. */ |
| if (mode & S_ISUID) |
| return false; |
| |
| /* Executable setgid files should not get pinned to the filesystem. */ |
| if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) |
| return false; |
| |
| /* Hardlinking to unreadable or unwritable sources is dangerous. */ |
| if (inode_permission(mnt_userns, inode, MAY_READ | MAY_WRITE)) |
| return false; |
| |
| return true; |
| } |
| |
| /** |
| * may_linkat - Check permissions for creating a hardlink |
| * @mnt_userns: user namespace of the mount the inode was found from |
| * @link: the source to hardlink from |
| * |
| * Block hardlink when all of: |
| * - sysctl_protected_hardlinks enabled |
| * - fsuid does not match inode |
| * - hardlink source is unsafe (see safe_hardlink_source() above) |
| * - not CAP_FOWNER in a namespace with the inode owner uid mapped |
| * |
| * If the inode has been found through an idmapped mount the user namespace of |
| * the vfsmount must be passed through @mnt_userns. This function will then take |
| * care to map the inode according to @mnt_userns before checking permissions. |
| * On non-idmapped mounts or if permission checking is to be performed on the |
| * raw inode simply passs init_user_ns. |
| * |
| * Returns 0 if successful, -ve on error. |
| */ |
| int may_linkat(struct user_namespace *mnt_userns, const struct path *link) |
| { |
| struct inode *inode = link->dentry->d_inode; |
| |
| /* Inode writeback is not safe when the uid or gid are invalid. */ |
| if (!uid_valid(i_uid_into_mnt(mnt_userns, inode)) || |
| !gid_valid(i_gid_into_mnt(mnt_userns, inode))) |
| return -EOVERFLOW; |
| |
| if (!sysctl_protected_hardlinks) |
| return 0; |
| |
| /* Source inode owner (or CAP_FOWNER) can hardlink all they like, |
| * otherwise, it must be a safe source. |
| */ |
| if (safe_hardlink_source(mnt_userns, inode) || |
| inode_owner_or_capable(mnt_userns, inode)) |
| return 0; |
| |
| audit_log_path_denied(AUDIT_ANOM_LINK, "linkat"); |
| return -EPERM; |
| } |
| |
| /** |
| * may_create_in_sticky - Check whether an O_CREAT open in a sticky directory |
| * should be allowed, or not, on files that already |
| * exist. |
| * @mnt_userns: user namespace of the mount the inode was found from |
| * @nd: nameidata pathwalk data |
| * @inode: the inode of the file to open |
| * |
| * Block an O_CREAT open of a FIFO (or a regular file) when: |
| * - sysctl_protected_fifos (or sysctl_protected_regular) is enabled |
| * - the file already exists |
| * - we are in a sticky directory |
| * - we don't own the file |
| * - the owner of the directory doesn't own the file |
| * - the directory is world writable |
| * If the sysctl_protected_fifos (or sysctl_protected_regular) is set to 2 |
| * the directory doesn't have to be world writable: being group writable will |
| * be enough. |
| * |
| * If the inode has been found through an idmapped mount the user namespace of |
| * the vfsmount must be passed through @mnt_userns. This function will then take |
| * care to map the inode according to @mnt_userns before checking permissions. |
| * On non-idmapped mounts or if permission checking is to be performed on the |
| * raw inode simply passs init_user_ns. |
| * |
| * Returns 0 if the open is allowed, -ve on error. |
| */ |
| static int may_create_in_sticky(struct user_namespace *mnt_userns, |
| struct nameidata *nd, struct inode *const inode) |
| { |
| umode_t dir_mode = nd->dir_mode; |
| kuid_t dir_uid = nd->dir_uid; |
| |
| if ((!sysctl_protected_fifos && S_ISFIFO(inode->i_mode)) || |
| (!sysctl_protected_regular && S_ISREG(inode->i_mode)) || |
| likely(!(dir_mode & S_ISVTX)) || |
| uid_eq(i_uid_into_mnt(mnt_userns, inode), dir_uid) || |
| uid_eq(current_fsuid(), i_uid_into_mnt(mnt_userns, inode))) |
| return 0; |
| |
| if (likely(dir_mode & 0002) || |
| (dir_mode & 0020 && |
| ((sysctl_protected_fifos >= 2 && S_ISFIFO(inode->i_mode)) || |
| (sysctl_protected_regular >= 2 && S_ISREG(inode->i_mode))))) { |
| const char *operation = S_ISFIFO(inode->i_mode) ? |
| "sticky_create_fifo" : |
| "sticky_create_regular"; |
| audit_log_path_denied(AUDIT_ANOM_CREAT, operation); |
| return -EACCES; |
| } |
| return 0; |
| } |
| |
| /* |
| * follow_up - Find the mountpoint of path's vfsmount |
| * |
| * Given a path, find the mountpoint of its source file system. |
| * Replace @path with the path of the mountpoint in the parent mount. |
| * Up is towards /. |
| * |
| * Return 1 if we went up a level and 0 if we were already at the |
| * root. |
| */ |
| int follow_up(struct path *path) |
| { |
| struct mount *mnt = real_mount(path->mnt); |
| struct mount *parent; |
| struct dentry *mountpoint; |
| |
| read_seqlock_excl(&mount_lock); |
| parent = mnt->mnt_parent; |
| if (parent == mnt) { |
| read_sequnlock_excl(&mount_lock); |
| return 0; |
| } |
| mntget(&parent->mnt); |
| mountpoint = dget(mnt->mnt_mountpoint); |
| read_sequnlock_excl(&mount_lock); |
| dput(path->dentry); |
| path->dentry = mountpoint; |
| mntput(path->mnt); |
| path->mnt = &parent->mnt; |
| return 1; |
| } |
| EXPORT_SYMBOL(follow_up); |
| |
| static bool choose_mountpoint_rcu(struct mount *m, const struct path *root, |
| struct path *path, unsigned *seqp) |
| { |
| while (mnt_has_parent(m)) { |
| struct dentry *mountpoint = m->mnt_mountpoint; |
| |
| m = m->mnt_parent; |
| if (unlikely(root->dentry == mountpoint && |
| root->mnt == &m->mnt)) |
| break; |
| if (mountpoint != m->mnt.mnt_root) { |
| path->mnt = &m->mnt; |
| path->dentry = mountpoint; |
| *seqp = read_seqcount_begin(&mountpoint->d_seq); |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| static bool choose_mountpoint(struct mount *m, const struct path *root, |
| struct path *path) |
| { |
| bool found; |
| |
| rcu_read_lock(); |
| while (1) { |
| unsigned seq, mseq = read_seqbegin(&mount_lock); |
| |
| found = choose_mountpoint_rcu(m, root, path, &seq); |
| if (unlikely(!found)) { |
| if (!read_seqretry(&mount_lock, mseq)) |
| break; |
| } else { |
| if (likely(__legitimize_path(path, seq, mseq))) |
| break; |
| rcu_read_unlock(); |
| path_put(path); |
| rcu_read_lock(); |
| } |
| } |
| rcu_read_unlock(); |
| return found; |
| } |
| |
| /* |
| * Perform an automount |
| * - return -EISDIR to tell follow_managed() to stop and return the path we |
| * were called with. |
| */ |
| static int follow_automount(struct path *path, int *count, unsigned lookup_flags) |
| { |
| struct dentry *dentry = path->dentry; |
| |
| /* We don't want to mount if someone's just doing a stat - |
| * unless they're stat'ing a directory and appended a '/' to |
| * the name. |
| * |
| * We do, however, want to mount if someone wants to open or |
| * create a file of any type under the mountpoint, wants to |
| * traverse through the mountpoint or wants to open the |
| * mounted directory. Also, autofs may mark negative dentries |
| * as being automount points. These will need the attentions |
| * of the daemon to instantiate them before they can be used. |
| */ |
| if (!(lookup_flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY | |
| LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) && |
| dentry->d_inode) |
| return -EISDIR; |
| |
| if (count && (*count)++ >= MAXSYMLINKS) |
| return -ELOOP; |
| |
| return finish_automount(dentry->d_op->d_automount(path), path); |
| } |
| |
| /* |
| * mount traversal - out-of-line part. One note on ->d_flags accesses - |
| * dentries are pinned but not locked here, so negative dentry can go |
| * positive right under us. Use of smp_load_acquire() provides a barrier |
| * sufficient for ->d_inode and ->d_flags consistency. |
| */ |
| static int __traverse_mounts(struct path *path, unsigned flags, bool *jumped, |
| int *count, unsigned lookup_flags) |
| { |
| struct vfsmount *mnt = path->mnt; |
| bool need_mntput = false; |
| int ret = 0; |
| |
| while (flags & DCACHE_MANAGED_DENTRY) { |
| /* Allow the filesystem to manage the transit without i_mutex |
| * being held. */ |
| if (flags & DCACHE_MANAGE_TRANSIT) { |
| ret = path->dentry->d_op->d_manage(path, false); |
| flags = smp_load_acquire(&path->dentry->d_flags); |
| if (ret < 0) |
| break; |
| } |
| |
| if (flags & DCACHE_MOUNTED) { // something's mounted on it.. |
| struct vfsmount *mounted = lookup_mnt(path); |
| if (mounted) { // ... in our namespace |
| dput(path->dentry); |
| if (need_mntput) |
| mntput(path->mnt); |
| path->mnt = mounted; |
| path->dentry = dget(mounted->mnt_root); |
| // here we know it's positive |
| flags = path->dentry->d_flags; |
| need_mntput = true; |
| continue; |
| } |
| } |
| |
| if (!(flags & DCACHE_NEED_AUTOMOUNT)) |
| break; |
| |
| // uncovered automount point |
| ret = follow_automount(path, count, lookup_flags); |
| flags = smp_load_acquire(&path->dentry->d_flags); |
| if (ret < 0) |
| break; |
| } |
| |
| if (ret == -EISDIR) |
| ret = 0; |
| // possible if you race with several mount --move |
| if (need_mntput && path->mnt == mnt) |
| mntput(path->mnt); |
| if (!ret && unlikely(d_flags_negative(flags))) |
| ret = -ENOENT; |
| *jumped = need_mntput; |
| return ret; |
| } |
| |
| static inline int traverse_mounts(struct path *path, bool *jumped, |
| int *count, unsigned lookup_flags) |
| { |
| unsigned flags = smp_load_acquire(&path->dentry->d_flags); |
| |
| /* fastpath */ |
| if (likely(!(flags & DCACHE_MANAGED_DENTRY))) { |
| *jumped = false; |
| if (unlikely(d_flags_negative(flags))) |
| return -ENOENT; |
| return 0; |
| } |
| return __traverse_mounts(path, flags, jumped, count, lookup_flags); |
| } |
| |
| int follow_down_one(struct path *path) |
| { |
| struct vfsmount *mounted; |
| |
| mounted = lookup_mnt(path); |
| if (mounted) { |
| dput(path->dentry); |
| mntput(path->mnt); |
| path->mnt = mounted; |
| path->dentry = dget(mounted->mnt_root); |
| return 1; |
| } |
| return 0; |
| } |
| EXPORT_SYMBOL(follow_down_one); |
| |
| /* |
| * Follow down to the covering mount currently visible to userspace. At each |
| * point, the filesystem owning that dentry may be queried as to whether the |
| * caller is permitted to proceed or not. |
| */ |
| int follow_down(struct path *path) |
| { |
| struct vfsmount *mnt = path->mnt; |
| bool jumped; |
| int ret = traverse_mounts(path, &jumped, NULL, 0); |
| |
| if (path->mnt != mnt) |
| mntput(mnt); |
| return ret; |
| } |
| EXPORT_SYMBOL(follow_down); |
| |
| /* |
| * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if |
| * we meet a managed dentry that would need blocking. |
| */ |
| static bool __follow_mount_rcu(struct nameidata *nd, struct path *path) |
| { |
| struct dentry *dentry = path->dentry; |
| unsigned int flags = dentry->d_flags; |
| |
| if (likely(!(flags & DCACHE_MANAGED_DENTRY))) |
| return true; |
| |
| if (unlikely(nd->flags & LOOKUP_NO_XDEV)) |
| return false; |
| |
| for (;;) { |
| /* |
| * Don't forget we might have a non-mountpoint managed dentry |
| * that wants to block transit. |
| */ |
| if (unlikely(flags & DCACHE_MANAGE_TRANSIT)) { |
| int res = dentry->d_op->d_manage(path, true); |
| if (res) |
| return res == -EISDIR; |
| flags = dentry->d_flags; |
| } |
| |
| if (flags & DCACHE_MOUNTED) { |
| struct mount *mounted = __lookup_mnt(path->mnt, dentry); |
| if (mounted) { |
| path->mnt = &mounted->mnt; |
| dentry = path->dentry = mounted->mnt.mnt_root; |
| nd->state |= ND_JUMPED; |
| nd->next_seq = read_seqcount_begin(&dentry->d_seq); |
| flags = dentry->d_flags; |
| // makes sure that non-RCU pathwalk could reach |
| // this state. |
| if (read_seqretry(&mount_lock, nd->m_seq)) |
| return false; |
| continue; |
| } |
| if (read_seqretry(&mount_lock, nd->m_seq)) |
| return false; |
| } |
| return !(flags & DCACHE_NEED_AUTOMOUNT); |
| } |
| } |
| |
| static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry, |
| struct path *path) |
| { |
| bool jumped; |
| int ret; |
| |
| path->mnt = nd->path.mnt; |
| path->dentry = dentry; |
| if (nd->flags & LOOKUP_RCU) { |
| unsigned int seq = nd->next_seq; |
| if (likely(__follow_mount_rcu(nd, path))) |
| return 0; |
| // *path and nd->next_seq might've been clobbered |
| path->mnt = nd->path.mnt; |
| path->dentry = dentry; |
| nd->next_seq = seq; |
| if (!try_to_unlazy_next(nd, dentry)) |
| return -ECHILD; |
| } |
| ret = traverse_mounts(path, &jumped, &nd->total_link_count, nd->flags); |
| if (jumped) { |
| if (unlikely(nd->flags & LOOKUP_NO_XDEV)) |
| ret = -EXDEV; |
| else |
| nd->state |= ND_JUMPED; |
| } |
| if (unlikely(ret)) { |
| dput(path->dentry); |
| if (path->mnt != nd->path.mnt) |
| mntput(path->mnt); |
| } |
| return ret; |
| } |
| |
| /* |
| * This looks up the name in dcache and possibly revalidates the found dentry. |
| * NULL is returned if the dentry does not exist in the cache. |
| */ |
| static struct dentry *lookup_dcache(const struct qstr *name, |
| struct dentry *dir, |
| unsigned int flags) |
| { |
| struct dentry *dentry = d_lookup(dir, name); |
| if (dentry) { |
| int error = d_revalidate(dentry, flags); |
| if (unlikely(error <= 0)) { |
| if (!error) |
| d_invalidate(dentry); |
| dput(dentry); |
| return ERR_PTR(error); |
| } |
| } |
| return dentry; |
| } |
| |
| /* |
| * Parent directory has inode locked exclusive. This is one |
| * and only case when ->lookup() gets called on non in-lookup |
| * dentries - as the matter of fact, this only gets called |
| * when directory is guaranteed to have no in-lookup children |
| * at all. |
| */ |
| struct dentry *lookup_one_qstr_excl(const struct qstr *name, |
| struct dentry *base, |
| unsigned int flags) |
| { |
| struct dentry *dentry = lookup_dcache(name, base, flags); |
| struct dentry *old; |
| struct inode *dir = base->d_inode; |
| |
| if (dentry) |
| return dentry; |
| |
| /* Don't create child dentry for a dead directory. */ |
| if (unlikely(IS_DEADDIR(dir))) |
| return ERR_PTR(-ENOENT); |
| |
| dentry = d_alloc(base, name); |
| if (unlikely(!dentry)) |
| return ERR_PTR(-ENOMEM); |
| |
| old = dir->i_op->lookup(dir, dentry, flags); |
| if (unlikely(old)) { |
| dput(dentry); |
| dentry = old; |
| } |
| return dentry; |
| } |
| EXPORT_SYMBOL(lookup_one_qstr_excl); |
| |
| static struct dentry *lookup_fast(struct nameidata *nd) |
| { |
| struct dentry *dentry, *parent = nd->path.dentry; |
| int status = 1; |
| |
| /* |
| * Rename seqlock is not required here because in the off chance |
| * of a false negative due to a concurrent rename, the caller is |
| * going to fall back to non-racy lookup. |
| */ |
| if (nd->flags & LOOKUP_RCU) { |
| dentry = __d_lookup_rcu(parent, &nd->last, &nd->next_seq); |
| if (unlikely(!dentry)) { |
| if (!try_to_unlazy(nd)) |
| return ERR_PTR(-ECHILD); |
| return NULL; |
| } |
| |
| /* |
| * This sequence count validates that the parent had no |
| * changes while we did the lookup of the dentry above. |
| */ |
| if (read_seqcount_retry(&parent->d_seq, nd->seq)) |
| return ERR_PTR(-ECHILD); |
| |
| status = d_revalidate(dentry, nd->flags); |
| if (likely(status > 0)) |
| return dentry; |
| if (!try_to_unlazy_next(nd, dentry)) |
| return ERR_PTR(-ECHILD); |
| if (status == -ECHILD) |
| /* we'd been told to redo it in non-rcu mode */ |
| status = d_revalidate(dentry, nd->flags); |
| } else { |
| dentry = __d_lookup(parent, &nd->last); |
| if (unlikely(!dentry)) |
| return NULL; |
| status = d_revalidate(dentry, nd->flags); |
| } |
| if (unlikely(status <= 0)) { |
| if (!status) |
| d_invalidate(dentry); |
| dput(dentry); |
| return ERR_PTR(status); |
| } |
| return dentry; |
| } |
| |
| /* Fast lookup failed, do it the slow way */ |
| static struct dentry *__lookup_slow(const struct qstr *name, |
| struct dentry *dir, |
| unsigned int flags) |
| { |
| struct dentry *dentry, *old; |
| struct inode *inode = dir->d_inode; |
| DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq); |
| |
| /* Don't go there if it's already dead */ |
| if (unlikely(IS_DEADDIR(inode))) |
| return ERR_PTR(-ENOENT); |
| again: |
| dentry = d_alloc_parallel(dir, name, &wq); |
| if (IS_ERR(dentry)) |
| return dentry; |
| if (unlikely(!d_in_lookup(dentry))) { |
| int error = d_revalidate(dentry, flags); |
| if (unlikely(error <= 0)) { |
| if (!error) { |
| d_invalidate(dentry); |
| dput(dentry); |
| goto again; |
| } |
| dput(dentry); |
| dentry = ERR_PTR(error); |
| } |
| } else { |
| old = inode->i_op->lookup(inode, dentry, flags); |
| d_lookup_done(dentry); |
| if (unlikely(old)) { |
| dput(dentry); |
| dentry = old; |
| } |
| } |
| return dentry; |
| } |
| |
| static struct dentry *lookup_slow(const struct qstr *name, |
| struct dentry *dir, |
| unsigned int flags) |
| { |
| struct inode *inode = dir->d_inode; |
| struct dentry *res; |
| inode_lock_shared(inode); |
| res = __lookup_slow(name, dir, flags); |
| inode_unlock_shared(inode); |
| return res; |
| } |
| |
| static inline int may_lookup(struct user_namespace *mnt_userns, |
| struct nameidata *nd) |
| { |
| if (nd->flags & LOOKUP_RCU) { |
| int err = inode_permission(mnt_userns, nd->inode, MAY_EXEC|MAY_NOT_BLOCK); |
| if (err != -ECHILD || !try_to_unlazy(nd)) |
| return err; |
| } |
| return inode_permission(mnt_userns, nd->inode, MAY_EXEC); |
| } |
| |
| static int reserve_stack(struct nameidata *nd, struct path *link) |
| { |
| if (unlikely(nd->total_link_count++ >= MAXSYMLINKS)) |
| return -ELOOP; |
| |
| if (likely(nd->depth != EMBEDDED_LEVELS)) |
| return 0; |
| if (likely(nd->stack != nd->internal)) |
| return 0; |
| if (likely(nd_alloc_stack(nd))) |
| return 0; |
| |
| if (nd->flags & LOOKUP_RCU) { |
| // we need to grab link before we do unlazy. And we can't skip |
| // unlazy even if we fail to grab the link - cleanup needs it |
| bool grabbed_link = legitimize_path(nd, link, nd->next_seq); |
| |
| if (!try_to_unlazy(nd) || !grabbed_link) |
| return -ECHILD; |
| |
| if (nd_alloc_stack(nd)) |
| return 0; |
| } |
| return -ENOMEM; |
| } |
| |
| enum {WALK_TRAILING = 1, WALK_MORE = 2, WALK_NOFOLLOW = 4}; |
| |
| static const char *pick_link(struct nameidata *nd, struct path *link, |
| struct inode *inode, int flags) |
| { |
| struct saved *last; |
| const char *res; |
| int error = reserve_stack(nd, link); |
| |
| if (unlikely(error)) { |
| if (!(nd->flags & LOOKUP_RCU)) |
| path_put(link); |
| return ERR_PTR(error); |
| } |
| last = nd->stack + nd->depth++; |
| last->link = *link; |
| clear_delayed_call(&last->done); |
| last->seq = nd->next_seq; |
| |
| if (flags & WALK_TRAILING) { |
| error = may_follow_link(nd, inode); |
| if (unlikely(error)) |
| return ERR_PTR(error); |
| } |
| |
| if (unlikely(nd->flags & LOOKUP_NO_SYMLINKS) || |
| unlikely(link->mnt->mnt_flags & MNT_NOSYMFOLLOW)) |
| return ERR_PTR(-ELOOP); |
| |
| if (!(nd->flags & LOOKUP_RCU)) { |
| touch_atime(&last->link); |
| cond_resched(); |
| } else if (atime_needs_update(&last->link, inode)) { |
| if (!try_to_unlazy(nd)) |
| return ERR_PTR(-ECHILD); |
| touch_atime(&last->link); |
| } |
| |
| error = security_inode_follow_link(link->dentry, inode, |
| nd->flags & LOOKUP_RCU); |
| if (unlikely(error)) |
| return ERR_PTR(error); |
| |
| res = READ_ONCE(inode->i_link); |
| if (!res) { |
| const char * (*get)(struct dentry *, struct inode *, |
| struct delayed_call *); |
| get = inode->i_op->get_link; |
| if (nd->flags & LOOKUP_RCU) { |
| res = get(NULL, inode, &last->done); |
| if (res == ERR_PTR(-ECHILD) && try_to_unlazy(nd)) |
| res = get(link->dentry, inode, &last->done); |
| } else { |
| res = get(link->dentry, inode, &last->done); |
| } |
| if (!res) |
| goto all_done; |
| if (IS_ERR(res)) |
| return res; |
| } |
| if (*res == '/') { |
| error = nd_jump_root(nd); |
| if (unlikely(error)) |
| return ERR_PTR(error); |
| while (unlikely(*++res == '/')) |
| ; |
| } |
| if (*res) |
| return res; |
| all_done: // pure jump |
| put_link(nd); |
| return NULL; |
| } |
| |
| /* |
| * Do we need to follow links? We _really_ want to be able |
| * to do this check without having to look at inode->i_op, |
| * so we keep a cache of "no, this doesn't need follow_link" |
| * for the common case. |
| * |
| * NOTE: dentry must be what nd->next_seq had been sampled from. |
| */ |
| static const char *step_into(struct nameidata *nd, int flags, |
| struct dentry *dentry) |
| { |
| struct path path; |
| struct inode *inode; |
| int err = handle_mounts(nd, dentry, &path); |
| |
| if (err < 0) |
| return ERR_PTR(err); |
| inode = path.dentry->d_inode; |
| if (likely(!d_is_symlink(path.dentry)) || |
| ((flags & WALK_TRAILING) && !(nd->flags & LOOKUP_FOLLOW)) || |
| (flags & WALK_NOFOLLOW)) { |
| /* not a symlink or should not follow */ |
| if (nd->flags & LOOKUP_RCU) { |
| if (read_seqcount_retry(&path.dentry->d_seq, nd->next_seq)) |
| return ERR_PTR(-ECHILD); |
| if (unlikely(!inode)) |
| return ERR_PTR(-ENOENT); |
| } else { |
| dput(nd->path.dentry); |
| if (nd->path.mnt != path.mnt) |
| mntput(nd->path.mnt); |
| } |
| nd->path = path; |
| nd->inode = inode; |
| nd->seq = nd->next_seq; |
| return NULL; |
| } |
| if (nd->flags & LOOKUP_RCU) { |
| /* make sure that d_is_symlink above matches inode */ |
| if (read_seqcount_retry(&path.dentry->d_seq, nd->next_seq)) |
| return ERR_PTR(-ECHILD); |
| } else { |
| if (path.mnt == nd->path.mnt) |
| mntget(path.mnt); |
| } |
| return pick_link(nd, &path, inode, flags); |
| } |
| |
| static struct dentry *follow_dotdot_rcu(struct nameidata *nd) |
| { |
| struct dentry *parent, *old; |
| |
| if (path_equal(&nd->path, &nd->root)) |
| goto in_root; |
| if (unlikely(nd->path.dentry == nd->path.mnt->mnt_root)) { |
| struct path path; |
| unsigned seq; |
| if (!choose_mountpoint_rcu(real_mount(nd->path.mnt), |
| &nd->root, &path, &seq)) |
| goto in_root; |
| if (unlikely(nd->flags & LOOKUP_NO_XDEV)) |
| return ERR_PTR(-ECHILD); |
| nd->path = path; |
| nd->inode = path.dentry->d_inode; |
| nd->seq = seq; |
| // makes sure that non-RCU pathwalk could reach this state |
| if (read_seqretry(&mount_lock, nd->m_seq)) |
| return ERR_PTR(-ECHILD); |
| /* we know that mountpoint was pinned */ |
| } |
| old = nd->path.dentry; |
| parent = old->d_parent; |
| nd->next_seq = read_seqcount_begin(&parent->d_seq); |
| // makes sure that non-RCU pathwalk could reach this state |
| if (read_seqcount_retry(&old->d_seq, nd->seq)) |
| return ERR_PTR(-ECHILD); |
| if (unlikely(!path_connected(nd->path.mnt, parent))) |
| return ERR_PTR(-ECHILD); |
| return parent; |
| in_root: |
| if (read_seqretry(&mount_lock, nd->m_seq)) |
| return ERR_PTR(-ECHILD); |
| if (unlikely(nd->flags & LOOKUP_BENEATH)) |
| return ERR_PTR(-ECHILD); |
| nd->next_seq = nd->seq; |
| return nd->path.dentry; |
| } |
| |
| static struct dentry *follow_dotdot(struct nameidata *nd) |
| { |
| struct dentry *parent; |
| |
| if (path_equal(&nd->path, &nd->root)) |
| goto in_root; |
| if (unlikely(nd->path.dentry == nd->path.mnt->mnt_root)) { |
| struct path path; |
| |
| if (!choose_mountpoint(real_mount(nd->path.mnt), |
| &nd->root, &path)) |
| goto in_root; |
| path_put(&nd->path); |
| nd->path = path; |
| nd->inode = path.dentry->d_inode; |
| if (unlikely(nd->flags & LOOKUP_NO_XDEV)) |
| return ERR_PTR(-EXDEV); |
| } |
| /* rare case of legitimate dget_parent()... */ |
| parent = dget_parent(nd->path.dentry); |
| if (unlikely(!path_connected(nd->path.mnt, parent))) { |
| dput(parent); |
| return ERR_PTR(-ENOENT); |
| } |
| return parent; |
| |
| in_root: |
| if (unlikely(nd->flags & LOOKUP_BENEATH)) |
| return ERR_PTR(-EXDEV); |
| return dget(nd->path.dentry); |
| } |
| |
| static const char *handle_dots(struct nameidata *nd, int type) |
| { |
| if (type == LAST_DOTDOT) { |
| const char *error = NULL; |
| struct dentry *parent; |
| |
| if (!nd->root.mnt) { |
| error = ERR_PTR(set_root(nd)); |
| if (error) |
| return error; |
| } |
| if (nd->flags & LOOKUP_RCU) |
| parent = follow_dotdot_rcu(nd); |
| else |
| parent = follow_dotdot(nd); |
| if (IS_ERR(parent)) |
| return ERR_CAST(parent); |
| error = step_into(nd, WALK_NOFOLLOW, parent); |
| if (unlikely(error)) |
| return error; |
| |
| if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) { |
| /* |
| * If there was a racing rename or mount along our |
| * path, then we can't be sure that ".." hasn't jumped |
| * above nd->root (and so userspace should retry or use |
| * some fallback). |
| */ |
| smp_rmb(); |
| if (__read_seqcount_retry(&mount_lock.seqcount, nd->m_seq)) |
| return ERR_PTR(-EAGAIN); |
| if (__read_seqcount_retry(&rename_lock.seqcount, nd->r_seq)) |
| return ERR_PTR(-EAGAIN); |
| } |
| } |
| return NULL; |
| } |
| |
| static const char *walk_component(struct nameidata *nd, int flags) |
| { |
| struct dentry *dentry; |
| /* |
| * "." and ".." are special - ".." especially so because it has |
| * to be able to know about the current root directory and |
| * parent relationships. |
| */ |
| if (unlikely(nd->last_type != LAST_NORM)) { |
| if (!(flags & WALK_MORE) && nd->depth) |
| put_link(nd); |
| return handle_dots(nd, nd->last_type); |
| } |
| dentry = lookup_fast(nd); |
| if (IS_ERR(dentry)) |
| return ERR_CAST(dentry); |
| if (unlikely(!dentry)) { |
| dentry = lookup_slow(&nd->last, nd->path.dentry, nd->flags); |
| if (IS_ERR(dentry)) |
| return ERR_CAST(dentry); |
| } |
| if (!(flags & WALK_MORE) && nd->depth) |
| put_link(nd); |
| return step_into(nd, flags, dentry); |
| } |
| |
| /* |
| * We can do the critical dentry name comparison and hashing |
| * operations one word at a time, but we are limited to: |
| * |
| * - Architectures with fast unaligned word accesses. We could |
| * do a "get_unaligned()" if this helps and is sufficiently |
| * fast. |
| * |
| * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we |
| * do not trap on the (extremely unlikely) case of a page |
| * crossing operation. |
| * |
| * - Furthermore, we need an efficient 64-bit compile for the |
| * 64-bit case in order to generate the "number of bytes in |
| * the final mask". Again, that could be replaced with a |
| * efficient population count instruction or similar. |
| */ |
| #ifdef CONFIG_DCACHE_WORD_ACCESS |
| |
| #include <asm/word-at-a-time.h> |
| |
| #ifdef HASH_MIX |
| |
| /* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */ |
| |
| #elif defined(CONFIG_64BIT) |
| /* |
| * Register pressure in the mixing function is an issue, particularly |
| * on 32-bit x86, but almost any function requires one state value and |
| * one temporary. Instead, use a function designed for two state values |
| * and no temporaries. |
| * |
| * This function cannot create a collision in only two iterations, so |
| * we have two iterations to achieve avalanche. In those two iterations, |
| * we have six layers of mixing, which is enough to spread one bit's |
| * influence out to 2^6 = 64 state bits. |
| * |
| * Rotate constants are scored by considering either 64 one-bit input |
| * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the |
| * probability of that delta causing a change to each of the 128 output |
| * bits, using a sample of random initial states. |
| * |
| * The Shannon entropy of the computed probabilities is then summed |
| * to produce a score. Ideally, any input change has a 50% chance of |
| * toggling any given output bit. |
| * |
| * Mixing scores (in bits) for (12,45): |
| * Input delta: 1-bit 2-bit |
| * 1 round: 713.3 42542.6 |
| * 2 rounds: 2753.7 140389.8 |
| * 3 rounds: 5954.1 233458.2 |
| * 4 rounds: 7862.6 256672.2 |
| * Perfect: 8192 258048 |
| * (64*128) (64*63/2 * 128) |
| */ |
| #define HASH_MIX(x, y, a) \ |
| ( x ^= (a), \ |
| y ^= x, x = rol64(x,12),\ |
| x += y, y = rol64(y,45),\ |
| y *= 9 ) |
| |
| /* |
| * Fold two longs into one 32-bit hash value. This must be fast, but |
| * latency isn't quite as critical, as there is a fair bit of additional |
| * work done before the hash value is used. |
| */ |
| static inline unsigned int fold_hash(unsigned long x, unsigned long y) |
| { |
| y ^= x * GOLDEN_RATIO_64; |
| y *= GOLDEN_RATIO_64; |
| return y >> 32; |
| } |
| |
| #else /* 32-bit case */ |
| |
| /* |
| * Mixing scores (in bits) for (7,20): |
| * Input delta: 1-bit 2-bit |
| * 1 round: 330.3 9201.6 |
| * 2 rounds: 1246.4 25475.4 |
| * 3 rounds: 1907.1 31295.1 |
| * 4 rounds: 2042.3 31718.6 |
| * Perfect: 2048 31744 |
| * (32*64) (32*31/2 * 64) |
| */ |
| #define HASH_MIX(x, y, a) \ |
| ( x ^= (a), \ |
| y ^= x, x = rol32(x, 7),\ |
| x += y, y = rol32(y,20),\ |
| y *= 9 ) |
| |
| static inline unsigned int fold_hash(unsigned long x, unsigned long y) |
| { |
| /* Use arch-optimized multiply if one exists */ |
| return __hash_32(y ^ __hash_32(x)); |
| } |
| |
| #endif |
| |
| /* |
| * Return the hash of a string of known length. This is carfully |
| * designed to match hash_name(), which is the more critical function. |
| * In particular, we must end by hashing a final word containing 0..7 |
| * payload bytes, to match the way that hash_name() iterates until it |
| * finds the delimiter after the name. |
| */ |
| unsigned int full_name_hash(const void *salt, const char *name, unsigned int len) |
| { |
| unsigned long a, x = 0, y = (unsigned long)salt; |
| |
| for (;;) { |
| if (!len) |
| goto done; |
| a = load_unaligned_zeropad(name); |
| if (len < sizeof(unsigned long)) |
| break; |
| HASH_MIX(x, y, a); |
| name += sizeof(unsigned long); |
| len -= sizeof(unsigned long); |
| } |
| x ^= a & bytemask_from_count(len); |
| done: |
| return fold_hash(x, y); |
| } |
| EXPORT_SYMBOL(full_name_hash); |
| |
| /* Return the "hash_len" (hash and length) of a null-terminated string */ |
| u64 hashlen_string(const void *salt, const char *name) |
| { |
| unsigned long a = 0, x = 0, y = (unsigned long)salt; |
| unsigned long adata, mask, len; |
| const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; |
| |
| len = 0; |
| goto inside; |
| |
| do { |
| HASH_MIX(x, y, a); |
| len += sizeof(unsigned long); |
| inside: |
| a = load_unaligned_zeropad(name+len); |
| } while (!has_zero(a, &adata, &constants)); |
| |
| adata = prep_zero_mask(a, adata, &constants); |
| mask = create_zero_mask(adata); |
| x ^= a & zero_bytemask(mask); |
| |
| return hashlen_create(fold_hash(x, y), len + find_zero(mask)); |
| } |
| EXPORT_SYMBOL(hashlen_string); |
| |
| /* |
| * Calculate the length and hash of the path component, and |
| * return the "hash_len" as the result. |
| */ |
| static inline u64 hash_name(const void *salt, const char *name) |
| { |
| unsigned long a = 0, b, x = 0, y = (unsigned long)salt; |
| unsigned long adata, bdata, mask, len; |
| const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; |
| |
| len = 0; |
| goto inside; |
| |
| do { |
| HASH_MIX(x, y, a); |
| len += sizeof(unsigned long); |
| inside: |
| a = load_unaligned_zeropad(name+len); |
| b = a ^ REPEAT_BYTE('/'); |
| } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants))); |
| |
| adata = prep_zero_mask(a, adata, &constants); |
| bdata = prep_zero_mask(b, bdata, &constants); |
| mask = create_zero_mask(adata | bdata); |
| x ^= a & zero_bytemask(mask); |
| |
| return hashlen_create(fold_hash(x, y), len + find_zero(mask)); |
| } |
| |
| #else /* !CONFIG_DCACHE_WORD_ACCESS: Slow, byte-at-a-time version */ |
| |
| /* Return the hash of a string of known length */ |
| unsigned int full_name_hash(const void *salt, const char *name, unsigned int len) |
| { |
| unsigned long hash = init_name_hash(salt); |
| while (len--) |
| hash = partial_name_hash((unsigned char)*name++, hash); |
| return end_name_hash(hash); |
| } |
| EXPORT_SYMBOL(full_name_hash); |
| |
| /* Return the "hash_len" (hash and length) of a null-terminated string */ |
| u64 hashlen_string(const void *salt, const char *name) |
| { |
| unsigned long hash = init_name_hash(salt); |
| unsigned long len = 0, c; |
| |
| c = (unsigned char)*name; |
| while (c) { |
| len++; |
| hash = partial_name_hash(c, hash); |
| c = (unsigned char)name[len]; |
| } |
| return hashlen_create(end_name_hash(hash), len); |
| } |
| EXPORT_SYMBOL(hashlen_string); |
| |
| /* |
| * We know there's a real path component here of at least |
| * one character. |
| */ |
| static inline u64 hash_name(const void *salt, const char *name) |
| { |
| unsigned long hash = init_name_hash(salt); |
| unsigned long len = 0, c; |
| |
| c = (unsigned char)*name; |
| do { |
| len++; |
| hash = partial_name_hash(c, hash); |
| c = (unsigned char)name[len]; |
| } while (c && c != '/'); |
| return hashlen_create(end_name_hash(hash), len); |
| } |
| |
| #endif |
| |
| /* |
| * Name resolution. |
| * This is the basic name resolution function, turning a pathname into |
| * the final dentry. We expect 'base' to be positive and a directory. |
| * |
| * Returns 0 and nd will have valid dentry and mnt on success. |
| * Returns error and drops reference to input namei data on failure. |
| */ |
| static int link_path_walk(const char *name, struct nameidata *nd) |
| { |
| int depth = 0; // depth <= nd->depth |
| int err; |
| |
| nd->last_type = LAST_ROOT; |
| nd->flags |= LOOKUP_PARENT; |
| if (IS_ERR(name)) |
| return PTR_ERR(name); |
| while (*name=='/') |
| name++; |
| if (!*name) { |
| nd->dir_mode = 0; // short-circuit the 'hardening' idiocy |
| return 0; |
| } |
| |
| /* At this point we know we have a real path component. */ |
| for(;;) { |
| struct user_namespace *mnt_userns; |
| const char *link; |
| u64 hash_len; |
| int type; |
| |
| mnt_userns = mnt_user_ns(nd->path.mnt); |
| err = may_lookup(mnt_userns, nd); |
| if (err) |
| return err; |
| |
| hash_len = hash_name(nd->path.dentry, name); |
| |
| type = LAST_NORM; |
| if (name[0] == '.') switch (hashlen_len(hash_len)) { |
| case 2: |
| if (name[1] == '.') { |
| type = LAST_DOTDOT; |
| nd->state |= ND_JUMPED; |
| } |
| break; |
| case 1: |
| type = LAST_DOT; |
| } |
| if (likely(type == LAST_NORM)) { |
| struct dentry *parent = nd->path.dentry; |
| nd->state &= ~ND_JUMPED; |
| if (unlikely(parent->d_flags & DCACHE_OP_HASH)) { |
| struct qstr this = { { .hash_len = hash_len }, .name = name }; |
| err = parent->d_op->d_hash(parent, &this); |
| if (err < 0) |
| return err; |
| hash_len = this.hash_len; |
| name = this.name; |
| } |
| } |
| |
| nd->last.hash_len = hash_len; |
| nd->last.name = name; |
| nd->last_type = type; |
| |
| name += hashlen_len(hash_len); |
| if (!*name) |
| goto OK; |
| /* |
| * If it wasn't NUL, we know it was '/'. Skip that |
| * slash, and continue until no more slashes. |
| */ |
| do { |
| name++; |
| } while (unlikely(*name == '/')); |
| if (unlikely(!*name)) { |
| OK: |
| /* pathname or trailing symlink, done */ |
| if (!depth) { |
| nd->dir_uid = i_uid_into_mnt(mnt_userns, nd->inode); |
| nd->dir_mode = nd->inode->i_mode; |
| nd->flags &= ~LOOKUP_PARENT; |
| return 0; |
| } |
| /* last component of nested symlink */ |
| name = nd->stack[--depth].name; |
| link = walk_component(nd, 0); |
| } else { |
| /* not the last component */ |
| link = walk_component(nd, WALK_MORE); |
| } |
| if (unlikely(link)) { |
| if (IS_ERR(link)) |
| return PTR_ERR(link); |
| /* a symlink to follow */ |
| nd->stack[depth++].name = name; |
| name = link; |
| continue; |
| } |
| if (unlikely(!d_can_lookup(nd->path.dentry))) { |
| if (nd->flags & LOOKUP_RCU) { |
| if (!try_to_unlazy(nd)) |
| return -ECHILD; |
| } |
| return -ENOTDIR; |
| } |
| } |
| } |
| |
| /* must be paired with terminate_walk() */ |
| static const char *path_init(struct nameidata *nd, unsigned flags) |
| { |
| int error; |
| const char *s = nd->name->name; |
| |
| /* LOOKUP_CACHED requires RCU, ask caller to retry */ |
| if ((flags & (LOOKUP_RCU | LOOKUP_CACHED)) == LOOKUP_CACHED) |
| return ERR_PTR(-EAGAIN); |
| |
| if (!*s) |
| flags &= ~LOOKUP_RCU; |
| if (flags & LOOKUP_RCU) |
| rcu_read_lock(); |
| else |
| nd->seq = nd->next_seq = 0; |
| |
| nd->flags = flags; |
| nd->state |= ND_JUMPED; |
| |
| nd->m_seq = __read_seqcount_begin(&mount_lock.seqcount); |
| nd->r_seq = __read_seqcount_begin(&rename_lock.seqcount); |
| smp_rmb(); |
| |
| if (nd->state & ND_ROOT_PRESET) { |
| struct dentry *root = nd->root.dentry; |
| struct inode *inode = root->d_inode; |
| if (*s && unlikely(!d_can_lookup(root))) |
| return ERR_PTR(-ENOTDIR); |
| nd->path = nd->root; |
| nd->inode = inode; |
| if (flags & LOOKUP_RCU) { |
| nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); |
| nd->root_seq = nd->seq; |
| } else { |
| path_get(&nd->path); |
| } |
| return s; |
| } |
| |
| nd->root.mnt = NULL; |
| |
| /* Absolute pathname -- fetch the root (LOOKUP_IN_ROOT uses nd->dfd). */ |
| if (*s == '/' && !(flags & LOOKUP_IN_ROOT)) { |
| error = nd_jump_root(nd); |
| if (unlikely(error)) |
| return ERR_PTR(error); |
| return s; |
| } |
| |
| /* Relative pathname -- get the starting-point it is relative to. */ |
| if (nd->dfd == AT_FDCWD) { |
| if (flags & LOOKUP_RCU) { |
| struct fs_struct *fs = current->fs; |
| unsigned seq; |
| |
| do { |
| seq = read_seqcount_begin(&fs->seq); |
| nd->path = fs->pwd; |
| nd->inode = nd->path.dentry->d_inode; |
| nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); |
| } while (read_seqcount_retry(&fs->seq, seq)); |
| } else { |
| get_fs_pwd(current->fs, &nd->path); |
| nd->inode = nd->path.dentry->d_inode; |
| } |
| } else { |
| /* Caller must check execute permissions on the starting path component */ |
| struct fd f = fdget_raw(nd->dfd); |
| struct dentry *dentry; |
| |
| if (!f.file) |
| return ERR_PTR(-EBADF); |
| |
| dentry = f.file->f_path.dentry; |
| |
| if (*s && unlikely(!d_can_lookup(dentry))) { |
| fdput(f); |
| return ERR_PTR(-ENOTDIR); |
| } |
| |
| nd->path = f.file->f_path; |
| if (flags & LOOKUP_RCU) { |
| nd->inode = nd->path.dentry->d_inode; |
| nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); |
| } else { |
| path_get(&nd->path); |
| nd->inode = nd->path.dentry->d_inode; |
| } |
| fdput(f); |
| } |
| |
| /* For scoped-lookups we need to set the root to the dirfd as well. */ |
| if (flags & LOOKUP_IS_SCOPED) { |
| nd->root = nd->path; |
| if (flags & LOOKUP_RCU) { |
| nd->root_seq = nd->seq; |
| } else { |
| path_get(&nd->root); |
| nd->state |= ND_ROOT_GRABBED; |
| } |
| } |
| return s; |
| } |
| |
| static inline const char *lookup_last(struct nameidata *nd) |
| { |
| if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len]) |
| nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; |
| |
| return walk_component(nd, WALK_TRAILING); |
| } |
| |
| static int handle_lookup_down(struct nameidata *nd) |
| { |
| if (!(nd->flags & LOOKUP_RCU)) |
| dget(nd->path.dentry); |
| nd->next_seq = nd->seq; |
| return PTR_ERR(step_into(nd, WALK_NOFOLLOW, nd->path.dentry)); |
| } |
| |
| /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ |
| static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path) |
| { |
| const char *s = path_init(nd, flags); |
| int err; |
| |
| if (unlikely(flags & LOOKUP_DOWN) && !IS_ERR(s)) { |
| err = handle_lookup_down(nd); |
| if (unlikely(err < 0)) |
| s = ERR_PTR(err); |
| } |
| |
| while (!(err = link_path_walk(s, nd)) && |
| (s = lookup_last(nd)) != NULL) |
| ; |
| if (!err && unlikely(nd->flags & LOOKUP_MOUNTPOINT)) { |
| err = handle_lookup_down(nd); |
| nd->state &= ~ND_JUMPED; // no d_weak_revalidate(), please... |
| } |
| if (!err) |
| err = complete_walk(nd); |
| |
| if (!err && nd->flags & LOOKUP_DIRECTORY) |
| if (!d_can_lookup(nd->path.dentry)) |
| err = -ENOTDIR; |
| if (!err) { |
| *path = nd->path; |
| nd->path.mnt = NULL; |
| nd->path.dentry = NULL; |
| } |
| terminate_walk(nd); |
| return err; |
| } |
| |
| int filename_lookup(int dfd, struct filename *name, unsigned flags, |
| struct path *path, struct path *root) |
| { |
| int retval; |
| struct nameidata nd; |
| if (IS_ERR(name)) |
| return PTR_ERR(name); |
| set_nameidata(&nd, dfd, name, root); |
| retval = path_lookupat(&nd, flags | LOOKUP_RCU, path); |
| if (unlikely(retval == -ECHILD)) |
| retval = path_lookupat(&nd, flags, path); |
| if (unlikely(retval == -ESTALE)) |
| retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path); |
| |
| if (likely(!retval)) |
| audit_inode(name, path->dentry, |
| flags & LOOKUP_MOUNTPOINT ? AUDIT_INODE_NOEVAL : 0); |
| restore_nameidata(); |
| return retval; |
| } |
| |
| /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ |
| static int path_parentat(struct nameidata *nd, unsigned flags, |
| struct path *parent) |
| { |
| const char *s = path_init(nd, flags); |
| int err = link_path_walk(s, nd); |
| if (!err) |
| err = complete_walk(nd); |
| if (!err) { |
| *parent = nd->path; |
| nd->path.mnt = NULL; |
| nd->path.dentry = NULL; |
| } |
| terminate_walk(nd); |
| return err; |
| } |
| |
| /* Note: this does not consume "name" */ |
| static int __filename_parentat(int dfd, struct filename *name, |
| unsigned int flags, struct path *parent, |
| struct qstr *last, int *type, |
| const struct path *root) |
| { |
| int retval; |
| struct nameidata nd; |
| |
| if (IS_ERR(name)) |
| return PTR_ERR(name); |
| set_nameidata(&nd, dfd, name, root); |
| retval = path_parentat(&nd, flags | LOOKUP_RCU, parent); |
| if (unlikely(retval == -ECHILD)) |
| retval = path_parentat(&nd, flags, parent); |
| if (unlikely(retval == -ESTALE)) |
| retval = path_parentat(&nd, flags | LOOKUP_REVAL, parent); |
| if (likely(!retval)) { |
| *last = nd.last; |
| *type = nd.last_type; |
| audit_inode(name, parent->dentry, AUDIT_INODE_PARENT); |
| } |
| restore_nameidata(); |
| return retval; |
| } |
| |
| static int filename_parentat(int dfd, struct filename *name, |
| unsigned int flags, struct path *parent, |
| struct qstr *last, int *type) |
| { |
| return __filename_parentat(dfd, name, flags, parent, last, type, NULL); |
| } |
| |
| /* does lookup, returns the object with parent locked */ |
| static struct dentry *__kern_path_locked(struct filename *name, struct path *path) |
| { |
| struct dentry *d; |
| struct qstr last; |
| int type, error; |
| |
| error = filename_parentat(AT_FDCWD, name, 0, path, &last, &type); |
| if (error) |
| return ERR_PTR(error); |
| if (unlikely(type != LAST_NORM)) { |
| path_put(path); |
| return ERR_PTR(-EINVAL); |
| } |
| inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT); |
| d = lookup_one_qstr_excl(&last, path->dentry, 0); |
| if (IS_ERR(d)) { |
| inode_unlock(path->dentry->d_inode); |
| path_put(path); |
| } |
| return d; |
| } |
| |
| struct dentry *kern_path_locked(const char *name, struct path *path) |
| { |
| struct filename *filename = getname_kernel(name); |
| struct dentry *res = __kern_path_locked(filename, path); |
| |
| putname(filename); |
| return res; |
| } |
| |
| int kern_path(const char *name, unsigned int flags, struct path *path) |
| { |
| struct filename *filename = getname_kernel(name); |
| int ret = filename_lookup(AT_FDCWD, filename, flags, path, NULL); |
| |
| putname(filename); |
| return ret; |
| |
| } |
| EXPORT_SYMBOL(kern_path); |
| |
| /** |
| * vfs_path_parent_lookup - lookup a parent path relative to a dentry-vfsmount pair |
| * @filename: filename structure |
| * @flags: lookup flags |
| * @parent: pointer to struct path to fill |
| * @last: last component |
| * @type: type of the last component |
| * @root: pointer to struct path of the base directory |
| */ |
| int vfs_path_parent_lookup(struct filename *filename, unsigned int flags, |
| struct path *parent, struct qstr *last, int *type, |
| const struct path *root) |
| { |
| return __filename_parentat(AT_FDCWD, filename, flags, parent, last, |
| type, root); |
| } |
| EXPORT_SYMBOL(vfs_path_parent_lookup); |
| |
| /** |
| * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair |
| * @dentry: pointer to dentry of the base directory |
| * @mnt: pointer to vfs mount of the base directory |
| * @name: pointer to file name |
| * @flags: lookup flags |
| * @path: pointer to struct path to fill |
| */ |
| int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, |
| const char *name, unsigned int flags, |
| struct path *path) |
| { |
| struct filename *filename; |
| struct path root = {.mnt = mnt, .dentry = dentry}; |
| int ret; |
| |
| filename = getname_kernel(name); |
| /* the first argument of filename_lookup() is ignored with root */ |
| ret = filename_lookup(AT_FDCWD, filename, flags, path, &root); |
| putname(filename); |
| return ret; |
| } |
| EXPORT_SYMBOL(vfs_path_lookup); |
| |
| static int lookup_one_common(struct user_namespace *mnt_userns, |
| const char *name, struct dentry *base, int len, |
| struct qstr *this) |
| { |
| this->name = name; |
| this->len = len; |
| this->hash = full_name_hash(base, name, len); |
| if (!len) |
| return -EACCES; |
| |
| if (unlikely(name[0] == '.')) { |
| if (len < 2 || (len == 2 && name[1] == '.')) |
| return -EACCES; |
| } |
| |
| while (len--) { |
| unsigned int c = *(const unsigned char *)name++; |
| if (c == '/' || c == '\0') |
| return -EACCES; |
| } |
| /* |
| * See if the low-level filesystem might want |
| * to use its own hash.. |
| */ |
| if (base->d_flags & DCACHE_OP_HASH) { |
| int err = base->d_op->d_hash(base, this); |
| if (err < 0) |
| return err; |
| } |
| |
| return inode_permission(mnt_userns, base->d_inode, MAY_EXEC); |
| } |
| |
| /** |
| * try_lookup_one_len - filesystem helper to lookup single pathname component |
| * @name: pathname component to lookup |
| * @base: base directory to lookup from |
| * @len: maximum length @len should be interpreted to |
| * |
| * Look up a dentry by name in the dcache, returning NULL if it does not |
| * currently exist. The function does not try to create a dentry. |
| * |
| * Note that this routine is purely a helper for filesystem usage and should |
| * not be called by generic code. |
| * |
| * The caller must hold base->i_mutex. |
| */ |
| struct dentry *try_lookup_one_len(const char *name, struct dentry *base, int len) |
| { |
| struct qstr this; |
| int err; |
| |
| WARN_ON_ONCE(!inode_is_locked(base->d_inode)); |
| |
| err = lookup_one_common(&init_user_ns, name, base, len, &this); |
| if (err) |
| return ERR_PTR(err); |
| |
| return lookup_dcache(&this, base, 0); |
| } |
| EXPORT_SYMBOL(try_lookup_one_len); |
| |
| /** |
| * lookup_one_len - filesystem helper to lookup single pathname component |
| * @name: pathname component to lookup |
| * @base: base directory to lookup from |
| * @len: maximum length @len should be interpreted to |
| * |
| * Note that this routine is purely a helper for filesystem usage and should |
| * not be called by generic code. |
| * |
| * The caller must hold base->i_mutex. |
| */ |
| struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) |
| { |
| struct dentry *dentry; |
| struct qstr this; |
| int err; |
| |
| WARN_ON_ONCE(!inode_is_locked(base->d_inode)); |
| |
| err = lookup_one_common(&init_user_ns, name, base, len, &this); |
| if (err) |
| return ERR_PTR(err); |
| |
| dentry = lookup_dcache(&this, base, 0); |
| return dentry ? dentry : __lookup_slow(&this, base, 0); |
| } |
| EXPORT_SYMBOL(lookup_one_len); |
| |
| /** |
| * lookup_one - filesystem helper to lookup single pathname component |
| * @mnt_userns: user namespace of the mount the lookup is performed from |
| * @name: pathname component to lookup |
| * @base: base directory to lookup from |
| * @len: maximum length @len should be interpreted to |
| * |
| * Note that this routine is purely a helper for filesystem usage and should |
| * not be called by generic code. |
| * |
| * The caller must hold base->i_mutex. |
| */ |
| struct dentry *lookup_one(struct user_namespace *mnt_userns, const char *name, |
| struct dentry *base, int len) |
| { |
| struct dentry *dentry; |
| struct qstr this; |
| int err; |
| |
| WARN_ON_ONCE(!inode_is_locked(base->d_inode)); |
| |
| err = lookup_one_common(mnt_userns, name, base, len, &this); |
| if (err) |
| return ERR_PTR(err); |
| |
| dentry = lookup_dcache(&this, base, 0); |
| return dentry ? dentry : __lookup_slow(&this, base, 0); |
| } |
| EXPORT_SYMBOL(lookup_one); |
| |
| /** |
| * lookup_one_unlocked - filesystem helper to lookup single pathname component |
| * @mnt_userns: idmapping of the mount the lookup is performed from |
| * @name: pathname component to lookup |
| * @base: base directory to lookup from |
| * @len: maximum length @len should be interpreted to |
| * |
| * Note that this routine is purely a helper for filesystem usage and should |
| * not be called by generic code. |
| * |
| * Unlike lookup_one_len, it should be called without the parent |
| * i_mutex held, and will take the i_mutex itself if necessary. |
| */ |
| struct dentry *lookup_one_unlocked(struct user_namespace *mnt_userns, |
| const char *name, struct dentry *base, |
| int len) |
| { |
| struct qstr this; |
| int err; |
| struct dentry *ret; |
| |
| err = lookup_one_common(mnt_userns, name, base, len, &this); |
| if (err) |
| return ERR_PTR(err); |
| |
| ret = lookup_dcache(&this, base, 0); |
| if (!ret) |
| ret = lookup_slow(&this, base, 0); |
| return ret; |
| } |
| EXPORT_SYMBOL(lookup_one_unlocked); |
| |
| /** |
| * lookup_one_positive_unlocked - filesystem helper to lookup single |
| * pathname component |
| * @mnt_userns: idmapping of the mount the lookup is performed from |
| * @name: pathname component to lookup |
| * @base: base directory to lookup from |
| * @len: maximum length @len should be interpreted to |
| * |
| * This helper will yield ERR_PTR(-ENOENT) on negatives. The helper returns |
| * known positive or ERR_PTR(). This is what most of the users want. |
| * |
| * Note that pinned negative with unlocked parent _can_ become positive at any |
| * time, so callers of lookup_one_unlocked() need to be very careful; pinned |
| * positives have >d_inode stable, so this one avoids such problems. |
| * |
| * Note that this routine is purely a helper for filesystem usage and should |
| * not be called by generic code. |
| * |
| * The helper should be called without i_mutex held. |
| */ |
| struct dentry *lookup_one_positive_unlocked(struct user_namespace *mnt_userns, |
| const char *name, |
| struct dentry *base, int len) |
| { |
| struct dentry *ret = lookup_one_unlocked(mnt_userns, name, base, len); |
| |
| if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) { |
| dput(ret); |
| ret = ERR_PTR(-ENOENT); |
| } |
| return ret; |
| } |
| EXPORT_SYMBOL(lookup_one_positive_unlocked); |
| |
| /** |
| * lookup_one_len_unlocked - filesystem helper to lookup single pathname component |
| * @name: pathname component to lookup |
| * @base: base directory to lookup from |
| * @len: maximum length @len should be interpreted to |
| * |
| * Note that this routine is purely a helper for filesystem usage and should |
| * not be called by generic code. |
| * |
| * Unlike lookup_one_len, it should be called without the parent |
| * i_mutex held, and will take the i_mutex itself if necessary. |
| */ |
| struct dentry *lookup_one_len_unlocked(const char *name, |
| struct dentry *base, int len) |
| { |
| return lookup_one_unlocked(&init_user_ns, name, base, len); |
| } |
| EXPORT_SYMBOL(lookup_one_len_unlocked); |
| |
| /* |
| * Like lookup_one_len_unlocked(), except that it yields ERR_PTR(-ENOENT) |
| * on negatives. Returns known positive or ERR_PTR(); that's what |
| * most of the users want. Note that pinned negative with unlocked parent |
| * _can_ become positive at any time, so callers of lookup_one_len_unlocked() |
| * need to be very careful; pinned positives have ->d_inode stable, so |
| * this one avoids such problems. |
| */ |
| struct dentry *lookup_positive_unlocked(const char *name, |
| struct dentry *base, int len) |
| { |
| return lookup_one_positive_unlocked(&init_user_ns, name, base, len); |
| } |
| EXPORT_SYMBOL(lookup_positive_unlocked); |
| |
| #ifdef CONFIG_UNIX98_PTYS |
| int path_pts(struct path *path) |
| { |
| /* Find something mounted on "pts" in the same directory as |
| * the input path. |
| */ |
| struct dentry *parent = dget_parent(path->dentry); |
| struct dentry *child; |
| struct qstr this = QSTR_INIT("pts", 3); |
| |
| if (unlikely(!path_connected(path->mnt, parent))) { |
| dput(parent); |
| return -ENOENT; |
| } |
| dput(path->dentry); |
| path->dentry = parent; |
| child = d_hash_and_lookup(parent, &this); |
| if (IS_ERR_OR_NULL(child)) |
| return -ENOENT; |
| |
| path->dentry = child; |
| dput(parent); |
| follow_down(path); |
| return 0; |
| } |
| #endif |
| |
| int user_path_at_empty(int dfd, const char __user *name, unsigned flags, |
| struct path *path, int *empty) |
| { |
| struct filename *filename = getname_flags(name, flags, empty); |
| int ret = filename_lookup(dfd, filename, flags, path, NULL); |
| |
| putname(filename); |
| return ret; |
| } |
| EXPORT_SYMBOL(user_path_at_empty); |
| |
| int __check_sticky(struct user_namespace *mnt_userns, struct inode *dir, |
| struct inode *inode) |
| { |
| kuid_t fsuid = current_fsuid(); |
| |
| if (uid_eq(i_uid_into_mnt(mnt_userns, inode), fsuid)) |
| return 0; |
| if (uid_eq(i_uid_into_mnt(mnt_userns, dir), fsuid)) |
| return 0; |
| return !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FOWNER); |
| } |
| EXPORT_SYMBOL(__check_sticky); |
| |
| /* |
| * Check whether we can remove a link victim from directory dir, check |
| * whether the type of victim is right. |
| * 1. We can't do it if dir is read-only (done in permission()) |
| * 2. We should have write and exec permissions on dir |
| * 3. We can't remove anything from append-only dir |
| * 4. We can't do anything with immutable dir (done in permission()) |
| * 5. If the sticky bit on dir is set we should either |
| * a. be owner of dir, or |
| * b. be owner of victim, or |
| * c. have CAP_FOWNER capability |
| * 6. If the victim is append-only or immutable we can't do antyhing with |
| * links pointing to it. |
| * 7. If the victim has an unknown uid or gid we can't change the inode. |
| * 8. If we were asked to remove a directory and victim isn't one - ENOTDIR. |
| * 9. If we were asked to remove a non-directory and victim isn't one - EISDIR. |
| * 10. We can't remove a root or mountpoint. |
| * 11. We don't allow removal of NFS sillyrenamed files; it's handled by |
| * nfs_async_unlink(). |
| */ |
| static int may_delete(struct user_namespace *mnt_userns, struct inode *dir, |
| struct dentry *victim, bool isdir) |
| { |
| struct inode *inode = d_backing_inode(victim); |
| int error; |
| |
| if (d_is_negative(victim)) |
| return -ENOENT; |
| BUG_ON(!inode); |
| |
| BUG_ON(victim->d_parent->d_inode != dir); |
| |
| /* Inode writeback is not safe when the uid or gid are invalid. */ |
| if (!uid_valid(i_uid_into_mnt(mnt_userns, inode)) || |
| !gid_valid(i_gid_into_mnt(mnt_userns, inode))) |
| return -EOVERFLOW; |
| |
| audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE); |
| |
| error = inode_permission(mnt_userns, dir, MAY_WRITE | MAY_EXEC); |
| if (error) |
| return error; |
| if (IS_APPEND(dir)) |
| return -EPERM; |
| |
| if (check_sticky(mnt_userns, dir, inode) || IS_APPEND(inode) || |
| IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) || |
| HAS_UNMAPPED_ID(mnt_userns, inode)) |
| return -EPERM; |
| if (isdir) { |
| if (!d_is_dir(victim)) |
| return -ENOTDIR; |
| if (IS_ROOT(victim)) |
| return -EBUSY; |
| } else if (d_is_dir(victim)) |
| return -EISDIR; |
| if (IS_DEADDIR(dir)) |
| return -ENOENT; |
| if (victim->d_flags & DCACHE_NFSFS_RENAMED) |
| return -EBUSY; |
| return 0; |
| } |
| |
| /* Check whether we can create an object with dentry child in directory |
| * dir. |
| * 1. We can't do it if child already exists (open has special treatment for |
| * this case, but since we are inlined it's OK) |
| * 2. We can't do it if dir is read-only (done in permission()) |
| * 3. We can't do it if the fs can't represent the fsuid or fsgid. |
| * 4. We should have write and exec permissions on dir |
| * 5. We can't do it if dir is immutable (done in permission()) |
| */ |
| static inline int may_create(struct user_namespace *mnt_userns, |
| struct inode *dir, struct dentry *child) |
| { |
| audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE); |
| if (child->d_inode) |
| return -EEXIST; |
| if (IS_DEADDIR(dir)) |
| return -ENOENT; |
| if (!fsuidgid_has_mapping(dir->i_sb, mnt_userns)) |
| return -EOVERFLOW; |
| |
| return inode_permission(mnt_userns, dir, MAY_WRITE | MAY_EXEC); |
| } |
| |
| static struct dentry *lock_two_directories(struct dentry *p1, struct dentry *p2) |
| { |
| struct dentry *p; |
| |
| p = d_ancestor(p2, p1); |
| if (p) { |
| inode_lock_nested(p2->d_inode, I_MUTEX_PARENT); |
| inode_lock_nested(p1->d_inode, I_MUTEX_PARENT2); |
| return p; |
| } |
| |
| p = d_ancestor(p1, p2); |
| inode_lock_nested(p1->d_inode, I_MUTEX_PARENT); |
| inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2); |
| return p; |
| } |
| |
| /* |
| * p1 and p2 should be directories on the same fs. |
| */ |
| struct dentry *lock_rename(struct dentry *p1, struct dentry *p2) |
| { |
| if (p1 == p2) { |
| inode_lock_nested(p1->d_inode, I_MUTEX_PARENT); |
| return NULL; |
| } |
| |
| mutex_lock(&p1->d_sb->s_vfs_rename_mutex); |
| return lock_two_directories(p1, p2); |
| } |
| EXPORT_SYMBOL(lock_rename); |
| |
| /* |
| * c1 and p2 should be on the same fs. |
| */ |
| struct dentry *lock_rename_child(struct dentry *c1, struct dentry *p2) |
| { |
| if (READ_ONCE(c1->d_parent) == p2) { |
| /* |
| * hopefully won't need to touch ->s_vfs_rename_mutex at all. |
| */ |
| inode_lock_nested(p2->d_inode, I_MUTEX_PARENT); |
| /* |
| * now that p2 is locked, nobody can move in or out of it, |
| * so the test below is safe. |
| */ |
| if (likely(c1->d_parent == p2)) |
| return NULL; |
| |
| /* |
| * c1 got moved out of p2 while we'd been taking locks; |
| * unlock and fall back to slow case. |
| */ |
| inode_unlock(p2->d_inode); |
| } |
| |
| mutex_lock(&c1->d_sb->s_vfs_rename_mutex); |
| /* |
| * nobody can move out of any directories on this fs. |
| */ |
| if (likely(c1->d_parent != p2)) |
| return lock_two_directories(c1->d_parent, p2); |
| |
| /* |
| * c1 got moved into p2 while we were taking locks; |
| * we need p2 locked and ->s_vfs_rename_mutex unlocked, |
| * for consistency with lock_rename(). |
| */ |
| inode_lock_nested(p2->d_inode, I_MUTEX_PARENT); |
| mutex_unlock(&c1->d_sb->s_vfs_rename_mutex); |
| return NULL; |
| } |
| EXPORT_SYMBOL(lock_rename_child); |
| |
| void unlock_rename(struct dentry *p1, struct dentry *p2) |
| { |
| inode_unlock(p1->d_inode); |
| if (p1 != p2) { |
| inode_unlock(p2->d_inode); |
| mutex_unlock(&p1->d_sb->s_vfs_rename_mutex); |
| } |
| } |
| EXPORT_SYMBOL |