From 2e601e1e8e4b330020a346c55ba111d49e0b188e Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Mon, 29 Jan 2024 20:34:38 -0500 Subject: mm: zswap: fix objcg use-after-free in entry destruction In the per-memcg LRU universe, LRU removal uses entry->objcg to determine which list count needs to be decreased. Drop the objcg reference after updating the LRU, to fix a possible use-after-free. Link: https://lkml.kernel.org/r/20240130013438.565167-1-hannes@cmpxchg.org Fixes: a65b0e7607cc ("zswap: make shrinking memcg-aware") Signed-off-by: Johannes Weiner Acked-by: Yosry Ahmed Reviewed-by: Nhat Pham Reviewed-by: Chengming Zhou Signed-off-by: Andrew Morton --- mm/zswap.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'mm/zswap.c') diff --git a/mm/zswap.c b/mm/zswap.c index ca25b676048e..0a94b197ed32 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -536,10 +536,6 @@ static struct zpool *zswap_find_zpool(struct zswap_entry *entry) */ static void zswap_free_entry(struct zswap_entry *entry) { - if (entry->objcg) { - obj_cgroup_uncharge_zswap(entry->objcg, entry->length); - obj_cgroup_put(entry->objcg); - } if (!entry->length) atomic_dec(&zswap_same_filled_pages); else { @@ -548,6 +544,10 @@ static void zswap_free_entry(struct zswap_entry *entry) atomic_dec(&entry->pool->nr_stored); zswap_pool_put(entry->pool); } + if (entry->objcg) { + obj_cgroup_uncharge_zswap(entry->objcg, entry->length); + obj_cgroup_put(entry->objcg); + } zswap_entry_cache_free(entry); atomic_dec(&zswap_stored_pages); zswap_update_total_size(); -- cgit v1.2.3