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authorJan Kara <jack@suse.cz>2023-06-01 12:58:25 +0200
committerChristian Brauner <brauner@kernel.org>2023-06-02 15:00:18 +0200
commit28eceeda130f5058074dd007d9c59d2e8bc5af2e (patch)
tree1b2ccadf12dbd14e5690640972a7916de73cbf8f /fs
parentf23ce757185319886ca80c4864ce5f81ac6cc9e9 (diff)
fs: Lock moved directories
When a directory is moved to a different directory, some filesystems (udf, ext4, ocfs2, f2fs, and likely gfs2, reiserfs, and others) need to update their pointer to the parent and this must not race with other operations on the directory. Lock the directories when they are moved. Although not all filesystems need this locking, we perform it in vfs_rename() because getting the lock ordering right is really difficult and we don't want to expose these locking details to filesystems. CC: stable@vger.kernel.org Signed-off-by: Jan Kara <jack@suse.cz> Message-Id: <20230601105830.13168-5-jack@suse.cz> Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/namei.c22
1 files changed, 14 insertions, 8 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 148570aabe74..6a5e26a529e1 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4731,7 +4731,7 @@ SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname
* sb->s_vfs_rename_mutex. We might be more accurate, but that's another
* story.
* c) we have to lock _four_ objects - parents and victim (if it exists),
- * and source (if it is not a directory).
+ * and source.
* And that - after we got ->i_mutex on parents (until then we don't know
* whether the target exists). Solution: try to be smart with locking
* order for inodes. We rely on the fact that tree topology may change
@@ -4815,10 +4815,16 @@ int vfs_rename(struct renamedata *rd)
take_dentry_name_snapshot(&old_name, old_dentry);
dget(new_dentry);
- if (!is_dir || (flags & RENAME_EXCHANGE))
- lock_two_nondirectories(source, target);
- else if (target)
- inode_lock(target);
+ /*
+ * Lock all moved children. Moved directories may need to change parent
+ * pointer so they need the lock to prevent against concurrent
+ * directory changes moving parent pointer. For regular files we've
+ * historically always done this. The lockdep locking subclasses are
+ * somewhat arbitrary but RENAME_EXCHANGE in particular can swap
+ * regular files and directories so it's difficult to tell which
+ * subclasses to use.
+ */
+ lock_two_inodes(source, target, I_MUTEX_NORMAL, I_MUTEX_NONDIR2);
error = -EPERM;
if (IS_SWAPFILE(source) || (target && IS_SWAPFILE(target)))
@@ -4866,9 +4872,9 @@ int vfs_rename(struct renamedata *rd)
d_exchange(old_dentry, new_dentry);
}
out:
- if (!is_dir || (flags & RENAME_EXCHANGE))
- unlock_two_nondirectories(source, target);
- else if (target)
+ if (source)
+ inode_unlock(source);
+ if (target)
inode_unlock(target);
dput(new_dentry);
if (!error) {