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authorAl Viro <viro@zeniv.linux.org.uk>2023-11-21 02:02:11 +0100
committerAl Viro <viro@zeniv.linux.org.uk>2023-11-25 08:54:14 +0100
commita8b0026847b8c43445c921ad2c85521c92eb175f (patch)
tree39078ede8594fab57ee0486e522655df86cb131f /fs/cachefiles
parentkill lock_two_inodes() (diff)
downloadlinux-a8b0026847b8c43445c921ad2c85521c92eb175f.tar.xz
linux-a8b0026847b8c43445c921ad2c85521c92eb175f.zip
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/cachefiles')
-rw-r--r--fs/cachefiles/namei.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 7bf7a5fcc045..7ade836beb58 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -305,6 +305,8 @@ try_again:
/* do the multiway lock magic */
trap = lock_rename(cache->graveyard, dir);
+ if (IS_ERR(trap))
+ return PTR_ERR(trap);
/* do some checks before getting the grave dentry */
if (rep->d_parent != dir || IS_DEADDIR(d_inode(rep))) {