From: Youling Tang <tangyouling@xxxxxxxxxx> Note that list_lru_from_memcg_idx() may return NULL, so it is necessary to error handle the return value to avoid triggering NULL pointer dereference BUG. The issue was triggered for discussion [1], Link [1]: https://lore.kernel.org/linux-bcachefs/84de6cb1-57bd-42f7-8029-4203820ef0b4@xxxxxxxxx/T/#m901bb26cdb1d9d4bacebf0d034f0a5a712cc93a6 Signed-off-by: Youling Tang <tangyouling@xxxxxxxxxx> --- mm/list_lru.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/list_lru.c b/mm/list_lru.c index 3fd64736bc45..ee7424c3879d 100644 --- a/mm/list_lru.c +++ b/mm/list_lru.c @@ -94,6 +94,9 @@ bool list_lru_add(struct list_lru *lru, struct list_head *item, int nid, spin_lock(&nlru->lock); if (list_empty(item)) { l = list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(memcg)); + if (!l) + goto out; + list_add_tail(item, &l->list); /* Set shrinker bit if the first element was added */ if (!l->nr_items++) @@ -102,6 +105,7 @@ bool list_lru_add(struct list_lru *lru, struct list_head *item, int nid, spin_unlock(&nlru->lock); return true; } +out: spin_unlock(&nlru->lock); return false; } -- 2.34.1
