UPSTREAM: dentry name snapshots
commit 49d31c2f389acfe83417083e1208422b4091cd9e upstream.
take_dentry_name_snapshot() takes a safe snapshot of dentry name;
if the name is a short one, it gets copied into caller-supplied
structure, otherwise an extra reference to external name is grabbed
(those are never modified). In either case the pointer to stable
string is stored into the same structure.
dentry must be held by the caller of take_dentry_name_snapshot(),
but may be freely dropped afterwards - the snapshot will stay
until destroyed by release_dentry_name_snapshot().
Intended use:
struct name_snapshot s;
take_dentry_name_snapshot(&s, dentry);
...
access s.name
...
release_dentry_name_snapshot(&s);
Replaces fsnotify_oldname_...(), gets used in fsnotify to obtain the name
to pass down with event.
CVE-2017-7533
Change-Id: I92a07b50c4380c329fb368cb8ad93d11a6f45f4f
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/fs/dcache.c b/fs/dcache.c
index 05b75fa..b2ae8fb 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -3367,3 +3367,30 @@
bdev_cache_init();
chrdev_init();
}
+
+void take_dentry_name_snapshot(struct name_snapshot *name, struct dentry *dentry)
+{
+ spin_lock(&dentry->d_lock);
+ if (unlikely(dname_external(dentry))) {
+ struct external_name *p = external_name(dentry);
+ atomic_inc(&p->u.count);
+ spin_unlock(&dentry->d_lock);
+ name->name = p->name;
+ } else {
+ memcpy(name->inline_name, dentry->d_iname, DNAME_INLINE_LEN);
+ spin_unlock(&dentry->d_lock);
+ name->name = name->inline_name;
+ }
+}
+EXPORT_SYMBOL(take_dentry_name_snapshot);
+
+void release_dentry_name_snapshot(struct name_snapshot *name)
+{
+ if (unlikely(name->name != name->inline_name)) {
+ struct external_name *p;
+ p = container_of(name->name, struct external_name, name[0]);
+ if (unlikely(atomic_dec_and_test(&p->u.count)))
+ kfree_rcu(p, u.head);
+ }
+}
+EXPORT_SYMBOL(release_dentry_name_snapshot);
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 6f0ce53..1488e13 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -620,7 +620,7 @@
{
int error;
struct dentry *dentry = NULL, *trap;
- const char *old_name;
+ struct name_snapshot old_name;
trap = lock_rename(new_dir, old_dir);
/* Source or destination directories don't exist? */
@@ -635,19 +635,19 @@
if (IS_ERR(dentry) || dentry == trap || dentry->d_inode)
goto exit;
- old_name = fsnotify_oldname_init(old_dentry->d_name.name);
+ take_dentry_name_snapshot(&old_name, old_dentry);
error = simple_rename(old_dir->d_inode, old_dentry, new_dir->d_inode,
dentry);
if (error) {
- fsnotify_oldname_free(old_name);
+ release_dentry_name_snapshot(&old_name);
goto exit;
}
d_move(old_dentry, dentry);
- fsnotify_move(old_dir->d_inode, new_dir->d_inode, old_name,
+ fsnotify_move(d_inode(old_dir), d_inode(new_dir), old_name.name,
S_ISDIR(old_dentry->d_inode->i_mode),
NULL, old_dentry);
- fsnotify_oldname_free(old_name);
+ release_dentry_name_snapshot(&old_name);
unlock_rename(new_dir, old_dir);
dput(dentry);
return old_dentry;
diff --git a/fs/namei.c b/fs/namei.c
index 5feb2d3..656b36d 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4177,11 +4177,11 @@
{
int error;
bool is_dir = d_is_dir(old_dentry);
- const unsigned char *old_name;
struct inode *source = old_dentry->d_inode;
struct inode *target = new_dentry->d_inode;
bool new_is_dir = false;
unsigned max_links = new_dir->i_sb->s_max_links;
+ struct name_snapshot old_name;
if (source == target)
return 0;
@@ -4231,7 +4231,7 @@
if (error)
return error;
- old_name = fsnotify_oldname_init(old_dentry->d_name.name);
+ take_dentry_name_snapshot(&old_name, old_dentry);
dget(new_dentry);
if (!is_dir || (flags & RENAME_EXCHANGE))
lock_two_nondirectories(source, target);
@@ -4292,14 +4292,14 @@
mutex_unlock(&target->i_mutex);
dput(new_dentry);
if (!error) {
- fsnotify_move(old_dir, new_dir, old_name, is_dir,
+ fsnotify_move(old_dir, new_dir, old_name.name, is_dir,
!(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
if (flags & RENAME_EXCHANGE) {
fsnotify_move(new_dir, old_dir, old_dentry->d_name.name,
new_is_dir, NULL, new_dentry);
}
}
- fsnotify_oldname_free(old_name);
+ release_dentry_name_snapshot(&old_name);
return error;
}
diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index 41e39102..e1f24ed 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -105,16 +105,20 @@
if (unlikely(!fsnotify_inode_watches_children(p_inode)))
__fsnotify_update_child_dentry_flags(p_inode);
else if (p_inode->i_fsnotify_mask & mask) {
+ struct name_snapshot name;
+
/* we are notifying a parent so come up with the new mask which
* specifies these are events which came from a child. */
mask |= FS_EVENT_ON_CHILD;
+ take_dentry_name_snapshot(&name, dentry);
if (path)
ret = fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH,
- dentry->d_name.name, 0);
+ name.name, 0);
else
ret = fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
- dentry->d_name.name, 0);
+ name.name, 0);
+ release_dentry_name_snapshot(&name);
}
dput(parent);
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index bac618a..331c1d6 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -530,4 +530,11 @@
return upper;
}
+struct name_snapshot {
+ const char *name;
+ char inline_name[DNAME_INLINE_LEN];
+};
+void take_dentry_name_snapshot(struct name_snapshot *, struct dentry *);
+void release_dentry_name_snapshot(struct name_snapshot *);
+
#endif /* __LINUX_DCACHE_H */
diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index 7ee1774..a778955 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -310,35 +310,4 @@
}
}
-#if defined(CONFIG_FSNOTIFY) /* notify helpers */
-
-/*
- * fsnotify_oldname_init - save off the old filename before we change it
- */
-static inline const unsigned char *fsnotify_oldname_init(const unsigned char *name)
-{
- return kstrdup(name, GFP_KERNEL);
-}
-
-/*
- * fsnotify_oldname_free - free the name we got from fsnotify_oldname_init
- */
-static inline void fsnotify_oldname_free(const unsigned char *old_name)
-{
- kfree(old_name);
-}
-
-#else /* CONFIG_FSNOTIFY */
-
-static inline const char *fsnotify_oldname_init(const unsigned char *name)
-{
- return NULL;
-}
-
-static inline void fsnotify_oldname_free(const unsigned char *old_name)
-{
-}
-
-#endif /* CONFIG_FSNOTIFY */
-
#endif /* _LINUX_FS_NOTIFY_H */
