[PATCH 5.16 0006/1017] mm: kfence: fix missing objcg housekeeping for SLAB

Greg Kroah-Hartman
2022-04-05T08:57:40Z

From: Muchun Song <songmuchun@bytedance.com>

commit ae085d7f9365de7da27ab5c0d16b12d51ea7fca9 upstream.

The objcg is not cleared and put for kfence object when it is freed,
which could lead to memory leak for struct obj_cgroup and wrong
statistics of NR_SLAB_RECLAIMABLE_B or NR_SLAB_UNRECLAIMABLE_B.

Since the last freed object's objcg is not cleared,
mem_cgroup_from_obj() could return the wrong memcg when this kfence
object, which is not charged to any objcgs, is reallocated to other
users.

A real word issue [1] is caused by this bug.

Link: https://lore.kernel.org/all/000000000000cabcb505dae9e577@google.com/ [1]
Reported-by: syzbot+f8c45ccc7d5d45fc5965@syzkaller.appspotmail.com
Fixes: d3fb45f370d9 ("mm, kfence: insert KFENCE hooks for SLAB")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
mm/slab.c | 1 +
1 file changed, 1 insertion(+)

--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3429,6 +3429,7 @@ static __always_inline void __cache_free

if (is_kfence_address(objp)) {
kmemleak_free_recursive(objp, cachep->flags);
+ memcg_slab_free_hook(cachep, &objp, 1);
__kfence_free(objp);
return;
}