| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * devtmpfs - kernel-maintained tmpfs-based /dev |
| * |
| * Copyright (C) 2009, Kay Sievers <kay.sievers@vrfy.org> |
| * |
| * During bootup, before any driver core device is registered, |
| * devtmpfs, a tmpfs-based filesystem is created. Every driver-core |
| * device which requests a device node, will add a node in this |
| * filesystem. |
| * By default, all devices are named after the name of the device, |
| * owned by root and have a default mode of 0600. Subsystems can |
| * overwrite the default setting if needed. |
| */ |
| |
| #include <linux/kernel.h> |
| #include <linux/syscalls.h> |
| #include <linux/mount.h> |
| #include <linux/device.h> |
| #include <linux/genhd.h> |
| #include <linux/namei.h> |
| #include <linux/fs.h> |
| #include <linux/shmem_fs.h> |
| #include <linux/ramfs.h> |
| #include <linux/sched.h> |
| #include <linux/slab.h> |
| #include <linux/kthread.h> |
| #include <linux/init_syscalls.h> |
| #include <uapi/linux/mount.h> |
| #include "base.h" |
| |
| static struct task_struct *thread; |
| |
| static int __initdata mount_dev = IS_ENABLED(CONFIG_DEVTMPFS_MOUNT); |
| |
| static DEFINE_SPINLOCK(req_lock); |
| |
| static struct req { |
| struct req *next; |
| struct completion done; |
| int err; |
| const char *name; |
| umode_t mode; /* 0 => delete */ |
| kuid_t uid; |
| kgid_t gid; |
| struct device *dev; |
| } *requests; |
| |
| static int __init mount_param(char *str) |
| { |
| mount_dev = simple_strtoul(str, NULL, 0); |
| return 1; |
| } |
| __setup("devtmpfs.mount=", mount_param); |
| |
| static struct vfsmount *mnt; |
| |
| static struct dentry *public_dev_mount(struct file_system_type *fs_type, int flags, |
| const char *dev_name, void *data) |
| { |
| struct super_block *s = mnt->mnt_sb; |
| int err; |
| |
| atomic_inc(&s->s_active); |
| down_write(&s->s_umount); |
| err = reconfigure_single(s, flags, data); |
| if (err < 0) { |
| deactivate_locked_super(s); |
| return ERR_PTR(err); |
| } |
| return dget(s->s_root); |
| } |
| |
| static struct file_system_type internal_fs_type = { |
| .name = "devtmpfs", |
| #ifdef CONFIG_TMPFS |
| .init_fs_context = shmem_init_fs_context, |
| .parameters = shmem_fs_parameters, |
| #else |
| .init_fs_context = ramfs_init_fs_context, |
| .parameters = ramfs_fs_parameters, |
| #endif |
| .kill_sb = kill_litter_super, |
| }; |
| |
| static struct file_system_type dev_fs_type = { |
| .name = "devtmpfs", |
| .mount = public_dev_mount, |
| }; |
| |
| #ifdef CONFIG_BLOCK |
| static inline int is_blockdev(struct device *dev) |
| { |
| return dev->class == &block_class; |
| } |
| #else |
| static inline int is_blockdev(struct device *dev) { return 0; } |
| #endif |
| |
| static int devtmpfs_submit_req(struct req *req, const char *tmp) |
| { |
| init_completion(&req->done); |
| |
| spin_lock(&req_lock); |
| req->next = requests; |
| requests = req; |
| spin_unlock(&req_lock); |
| |
| wake_up_process(thread); |
| wait_for_completion(&req->done); |
| |
| kfree(tmp); |
| |
| return req->err; |
| } |
| |
| int devtmpfs_create_node(struct device *dev) |
| { |
| const char *tmp = NULL; |
| struct req req; |
| |
| if (!thread) |
| return 0; |
| |
| req.mode = 0; |
| req.uid = GLOBAL_ROOT_UID; |
| req.gid = GLOBAL_ROOT_GID; |
| req.name = device_get_devnode(dev, &req.mode, &req.uid, &req.gid, &tmp); |
| if (!req.name) |
| return -ENOMEM; |
| |
| if (req.mode == 0) |
| req.mode = 0600; |
| if (is_blockdev(dev)) |
| req.mode |= S_IFBLK; |
| else |
| req.mode |= S_IFCHR; |
| |
| req.dev = dev; |
| |
| return devtmpfs_submit_req(&req, tmp); |
| } |
| |
| int devtmpfs_delete_node(struct device *dev) |
| { |
| const char *tmp = NULL; |
| struct req req; |
| |
| if (!thread) |
| return 0; |
| |
| req.name = device_get_devnode(dev, NULL, NULL, NULL, &tmp); |
| if (!req.name) |
| return -ENOMEM; |
| |
| req.mode = 0; |
| req.dev = dev; |
| |
| return devtmpfs_submit_req(&req, tmp); |
| } |
| |
| static int dev_mkdir(const char *name, umode_t mode) |
| { |
| struct dentry *dentry; |
| struct path path; |
| int err; |
| |
| dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_DIRECTORY); |
| if (IS_ERR(dentry)) |
| return PTR_ERR(dentry); |
| |
| err = vfs_mkdir(&init_user_ns, d_inode(path.dentry), dentry, mode); |
| if (!err) |
| /* mark as kernel-created inode */ |
| d_inode(dentry)->i_private = &thread; |
| done_path_create(&path, dentry); |
| return err; |
| } |
| |
| static int create_path(const char *nodepath) |
| { |
| char *path; |
| char *s; |
| int err = 0; |
| |
| /* parent directories do not exist, create them */ |
| path = kstrdup(nodepath, GFP_KERNEL); |
| if (!path) |
| return -ENOMEM; |
| |
| s = path; |
| for (;;) { |
| s = strchr(s, '/'); |
| if (!s) |
| break; |
| s[0] = '\0'; |
| err = dev_mkdir(path, 0755); |
| if (err && err != -EEXIST) |
| break; |
| s[0] = '/'; |
| s++; |
| } |
| kfree(path); |
| return err; |
| } |
| |
| static int handle_create(const char *nodename, umode_t mode, kuid_t uid, |
| kgid_t gid, struct device *dev) |
| { |
| struct dentry *dentry; |
| struct path path; |
| int err; |
| |
| dentry = kern_path_create(AT_FDCWD, nodename, &path, 0); |
| if (dentry == ERR_PTR(-ENOENT)) { |
| create_path(nodename); |
| dentry = kern_path_create(AT_FDCWD, nodename, &path, 0); |
| } |
| if (IS_ERR(dentry)) |
| return PTR_ERR(dentry); |
| |
| err = vfs_mknod(&init_user_ns, d_inode(path.dentry), dentry, mode, |
| dev->devt); |
| if (!err) { |
| struct iattr newattrs; |
| |
| newattrs.ia_mode = mode; |
| newattrs.ia_uid = uid; |
| newattrs.ia_gid = gid; |
| newattrs.ia_valid = ATTR_MODE|ATTR_UID|ATTR_GID; |
| inode_lock(d_inode(dentry)); |
| notify_change(&init_user_ns, dentry, &newattrs, NULL); |
| inode_unlock(d_inode(dentry)); |
| |
| /* mark as kernel-created inode */ |
| d_inode(dentry)->i_private = &thread; |
| } |
| done_path_create(&path, dentry); |
| return err; |
| } |
| |
| static int dev_rmdir(const char *name) |
| { |
| struct path parent; |
| struct dentry *dentry; |
| int err; |
| |
| dentry = kern_path_locked(name, &parent); |
| if (IS_ERR(dentry)) |
| return PTR_ERR(dentry); |
| if (d_really_is_positive(dentry)) { |
| if (d_inode(dentry)->i_private == &thread) |
| err = vfs_rmdir(&init_user_ns, d_inode(parent.dentry), |
| dentry); |
| else |
| err = -EPERM; |
| } else { |
| err = -ENOENT; |
| } |
| dput(dentry); |
| inode_unlock(d_inode(parent.dentry)); |
| path_put(&parent); |
| return err; |
| } |
| |
| static int delete_path(const char *nodepath) |
| { |
| char *path; |
| int err = 0; |
| |
| path = kstrdup(nodepath, GFP_KERNEL); |
| if (!path) |
| return -ENOMEM; |
| |
| for (;;) { |
| char *base; |
| |
| base = strrchr(path, '/'); |
| if (!base) |
| break; |
| base[0] = '\0'; |
| err = dev_rmdir(path); |
| if (err) |
| break; |
| } |
| |
| kfree(path); |
| return err; |
| } |
| |
| static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat) |
| { |
| /* did we create it */ |
| if (inode->i_private != &thread) |
| return 0; |
| |
| /* does the dev_t match */ |
| if (is_blockdev(dev)) { |
| if (!S_ISBLK(stat->mode)) |
| return 0; |
| } else { |
| if (!S_ISCHR(stat->mode)) |
| return 0; |
| } |
| if (stat->rdev != dev->devt) |
| return 0; |
| |
| /* ours */ |
| return 1; |
| } |
| |
| static int handle_remove(const char *nodename, struct device *dev) |
| { |
| struct path parent; |
| struct dentry *dentry; |
| int deleted = 0; |
| int err; |
| |
| dentry = kern_path_locked(nodename, &parent); |
| if (IS_ERR(dentry)) |
| return PTR_ERR(dentry); |
| |
| if (d_really_is_positive(dentry)) { |
| struct kstat stat; |
| struct path p = {.mnt = parent.mnt, .dentry = dentry}; |
| err = vfs_getattr(&p, &stat, STATX_TYPE | STATX_MODE, |
| AT_STATX_SYNC_AS_STAT); |
| if (!err && dev_mynode(dev, d_inode(dentry), &stat)) { |
| struct iattr newattrs; |
| /* |
| * before unlinking this node, reset permissions |
| * of possible references like hardlinks |
| */ |
| newattrs.ia_uid = GLOBAL_ROOT_UID; |
| newattrs.ia_gid = GLOBAL_ROOT_GID; |
| newattrs.ia_mode = stat.mode & ~0777; |
| newattrs.ia_valid = |
| ATTR_UID|ATTR_GID|ATTR_MODE; |
| inode_lock(d_inode(dentry)); |
| notify_change(&init_user_ns, dentry, &newattrs, NULL); |
| inode_unlock(d_inode(dentry)); |
| err = vfs_unlink(&init_user_ns, d_inode(parent.dentry), |
| dentry, NULL); |
| if (!err || err == -ENOENT) |
| deleted = 1; |
| } |
| } else { |
| err = -ENOENT; |
| } |
| dput(dentry); |
| inode_unlock(d_inode(parent.dentry)); |
| |
| path_put(&parent); |
| if (deleted && strchr(nodename, '/')) |
| delete_path(nodename); |
| return err; |
| } |
| |
| /* |
| * If configured, or requested by the commandline, devtmpfs will be |
| * auto-mounted after the kernel mounted the root filesystem. |
| */ |
| int __init devtmpfs_mount(void) |
| { |
| int err; |
| |
| if (!mount_dev) |
| return 0; |
| |
| if (!thread) |
| return 0; |
| |
| err = init_mount("devtmpfs", "dev", "devtmpfs", MS_SILENT, NULL); |
| if (err) |
| printk(KERN_INFO "devtmpfs: error mounting %i\n", err); |
| else |
| printk(KERN_INFO "devtmpfs: mounted\n"); |
| return err; |
| } |
| |
| static __initdata DECLARE_COMPLETION(setup_done); |
| |
| static int handle(const char *name, umode_t mode, kuid_t uid, kgid_t gid, |
| struct device *dev) |
| { |
| if (mode) |
| return handle_create(name, mode, uid, gid, dev); |
| else |
| return handle_remove(name, dev); |
| } |
| |
| static void __noreturn devtmpfs_work_loop(void) |
| { |
| while (1) { |
| spin_lock(&req_lock); |
| while (requests) { |
| struct req *req = requests; |
| requests = NULL; |
| spin_unlock(&req_lock); |
| while (req) { |
| struct req *next = req->next; |
| req->err = handle(req->name, req->mode, |
| req->uid, req->gid, req->dev); |
| complete(&req->done); |
| req = next; |
| } |
| spin_lock(&req_lock); |
| } |
| __set_current_state(TASK_INTERRUPTIBLE); |
| spin_unlock(&req_lock); |
| schedule(); |
| } |
| } |
| |
| static noinline int __init devtmpfs_setup(void *p) |
| { |
| int err; |
| |
| err = ksys_unshare(CLONE_NEWNS); |
| if (err) |
| goto out; |
| err = init_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, NULL); |
| if (err) |
| goto out; |
| init_chdir("/.."); /* will traverse into overmounted root */ |
| init_chroot("."); |
| out: |
| *(int *)p = err; |
| return err; |
| } |
| |
| /* |
| * The __ref is because devtmpfs_setup needs to be __init for the routines it |
| * calls. That call is done while devtmpfs_init, which is marked __init, |
| * synchronously waits for it to complete. |
| */ |
| static int __ref devtmpfsd(void *p) |
| { |
| int err = devtmpfs_setup(p); |
| |
| complete(&setup_done); |
| if (err) |
| return err; |
| devtmpfs_work_loop(); |
| return 0; |
| } |
| |
| /* |
| * Create devtmpfs instance, driver-core devices will add their device |
| * nodes here. |
| */ |
| int __init devtmpfs_init(void) |
| { |
| char opts[] = "mode=0755"; |
| int err; |
| |
| mnt = vfs_kern_mount(&internal_fs_type, 0, "devtmpfs", opts); |
| if (IS_ERR(mnt)) { |
| printk(KERN_ERR "devtmpfs: unable to create devtmpfs %ld\n", |
| PTR_ERR(mnt)); |
| return PTR_ERR(mnt); |
| } |
| err = register_filesystem(&dev_fs_type); |
| if (err) { |
| printk(KERN_ERR "devtmpfs: unable to register devtmpfs " |
| "type %i\n", err); |
| return err; |
| } |
| |
| thread = kthread_run(devtmpfsd, &err, "kdevtmpfs"); |
| if (!IS_ERR(thread)) { |
| wait_for_completion(&setup_done); |
| } else { |
| err = PTR_ERR(thread); |
| thread = NULL; |
| } |
| |
| if (err) { |
| printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err); |
| unregister_filesystem(&dev_fs_type); |
| return err; |
| } |
| |
| printk(KERN_INFO "devtmpfs: initialized\n"); |
| return 0; |
| } |