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authorAl Viro <viro@zeniv.linux.org.uk>2023-11-21 04:02:11 +0300
committerAl Viro <viro@zeniv.linux.org.uk>2023-11-25 10:54:14 +0300
commita8b0026847b8c43445c921ad2c85521c92eb175f (patch)
tree39078ede8594fab57ee0486e522655df86cb131f /fs/ecryptfs
parentdbd4540df2b2857a91593754275c02f3e415fc30 (diff)
downloadlinux-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.c2
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)