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mm: zswap: fix objcg use-after-free in entry destruction

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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: a65b0e7607 ("zswap: make shrinking memcg-aware")
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Reviewed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Johannes Weiner 2024-01-29 20:34:38 -05:00 committed by Andrew Morton
parent 4c2da3188b
commit 2e601e1e8e
1 changed files with 4 additions and 4 deletions
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8
mm/zswap.c
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@ -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();