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Al Viro
169b803397
the victim might've been rmdir'ed just before the lock_rename();
unlike the normal callers, we do not look the source up after the
parents are locked - we know it beforehand and just recheck that it's
still the child of what used to be its parent. Unfortunately,
the check is too weak - we don't spot a dead directory since its
->d_parent is unchanged, dentry is positive, etc. So we sail all
the way to ->rename(), with hosting filesystems _not_ expecting
to be asked renaming an rmdir'ed subdirectory.
The fix is easy, fortunately - the lock on parent is sufficient for
making IS_DEADDIR() on child safe.
Cc: [email protected]
Fixes: 9ae326a690 (CacheFiles: A cache that backs onto a mounted filesystem)
Signed-off-by: Al Viro <[email protected]>
Signed-off-by: David Howells <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>