6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: HyungJung Joo [ Upstream commit d227786ab1119669df4dc333a61510c52047cce4 ] mb_cache_destroy() calls shrinker_free() and then frees all cache entries and the cache itself, but it does not cancel the pending c_shrink_work work item first. If mb_cache_entry_create() schedules c_shrink_work via schedule_work() and the work item is still pending or running when mb_cache_destroy() runs, mb_cache_shrink_worker() will access the cache after its memory has been freed, causing a use-after-free. This is only reachable by a privileged user (root or CAP_SYS_ADMIN) who can trigger the last put of a mounted ext2/ext4/ocfs2 filesystem. Cancel the work item with cancel_work_sync() before calling shrinker_free(), ensuring the worker has finished and will not be rescheduled before the cache is torn down. Fixes: c2f3140fe2ec ("mbcache2: limit cache size") Signed-off-by: Hyungjung Joo Link: https://patch.msgid.link/20260317054556.1821600-1-jhj140711@gmail.com Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin --- fs/mbcache.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/mbcache.c b/fs/mbcache.c index 82aa7a35db26b..f8cd2e820fbb9 100644 --- a/fs/mbcache.c +++ b/fs/mbcache.c @@ -408,6 +408,7 @@ void mb_cache_destroy(struct mb_cache *cache) { struct mb_cache_entry *entry, *next; + cancel_work_sync(&cache->c_shrink_work); shrinker_free(cache->c_shrink); /* -- 2.53.0