5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jeff Layton <jlayton@kernel.org>
commit f42d0fda0c67695db6bc704b04b7c10240805377 upstream.
sunrpc_destroy_cache_detail() only cancels the global cache_cleaner
delayed_work when cache_list is empty. During per-netns teardown
cache_list is never empty because init_net's caches remain registered,
so the cancel never fires. After unlink, the caller proceeds to
cache_destroy_net() which kfrees the cache_detail while cache_clean()
may still hold a dangling pointer to it. The result is a
use-after-free: cache_dequeue() takes cd->queue_lock on freed memory,
and cache_put() dereferences cd->cache_put as a function pointer from
freed slab.
Drop the list_empty guard so that cancel_delayed_work_sync() always
runs, ensuring any in-flight cache_clean() completes before the
cache_detail is freed. Re-arm the cleaner afterwards if other caches
are still registered.
Fixes: 820f9442e711 ("SUNRPC: split cache creation and PipeFS registration")
Cc: <redacted>
Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260526-cache_cleaner_vs_destroy_no_sync-v1-1-a707a6fcfd32@kernel.org (local)
Signed-off-by: Chuck Lever <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sunrpc/cache.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -410,10 +410,9 @@ void sunrpc_destroy_cache_detail(struct
list_del_init(&cd->others);
spin_unlock(&cd->hash_lock);
spin_unlock(&cache_list_lock);
- if (list_empty(&cache_list)) {
- /* module must be being unloaded so its safe to kill the worker */
- cancel_delayed_work_sync(&cache_cleaner);
- }
+ cancel_delayed_work_sync(&cache_cleaner);
+ if (!list_empty(&cache_list))
+ queue_delayed_work(system_power_efficient_wq, &cache_cleaner, 0);
}
EXPORT_SYMBOL_GPL(sunrpc_destroy_cache_detail);