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| author | Al Viro <viro@zeniv.linux.org.uk> | 2023-11-21 04:02:11 +0300 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2023-11-25 10:54:14 +0300 |
| commit | a8b0026847b8c43445c921ad2c85521c92eb175f (patch) | |
| tree | 39078ede8594fab57ee0486e522655df86cb131f /fs/ecryptfs | |
| parent | dbd4540df2b2857a91593754275c02f3e415fc30 (diff) | |
| download | linux-a8b0026847b8c43445c921ad2c85521c92eb175f.tar.xz | |
rename(): avoid a deadlock in the case of parents having no common ancestor
... and fix the directory locking documentation and proof of correctness.
Holding ->s_vfs_rename_mutex *almost* prevents ->d_parent changes; the
case where we really don't want it is splicing the root of disconnected
tree to somewhere.
In other words, ->s_vfs_rename_mutex is sufficient to stabilize "X is an
ancestor of Y" only if X and Y are already in the same tree. Otherwise
it can go from false to true, and one can construct a deadlock on that.
Make lock_two_directories() report an error in such case and update the
callers of lock_rename()/lock_rename_child() to handle such errors.
And yes, such conditions are not impossible to create ;-/
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/ecryptfs')
| -rw-r--r-- | fs/ecryptfs/inode.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c index a25dd3d20008..8efd20dc902b 100644 --- a/fs/ecryptfs/inode.c +++ b/fs/ecryptfs/inode.c @@ -599,6 +599,8 @@ ecryptfs_rename(struct mnt_idmap *idmap, struct inode *old_dir, target_inode = d_inode(new_dentry); trap = lock_rename(lower_old_dir_dentry, lower_new_dir_dentry); + if (IS_ERR(trap)) + return PTR_ERR(trap); dget(lower_new_dentry); rc = -EINVAL; if (lower_old_dentry->d_parent != lower_old_dir_dentry) |