Commit ae085d7f authored by Muchun Song's avatar Muchun Song Committed by Linus Torvalds
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mm: kfence: fix missing objcg housekeeping for SLAB 

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: default avatar <syzbot+f8c45ccc7d5d45fc5965@syzkaller.appspotmail.com>
Fixes: d3fb45f3 ("mm, kfence: insert KFENCE hooks for SLAB")
Signed-off-by: default avatarMuchun 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: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f82da161

mm/slab.c

+1 −0
Original line number Diff line number Diff line
@@ -3422,6 +3422,7 @@ static __always_inline void __cache_free(struct kmem_cache *cachep, void *objp, 


	if (is_kfence_address(objp)) {

		kmemleak_free_recursive(objp, cachep->flags);

		memcg_slab_free_hook(cachep, &objp, 1);

		__kfence_free(objp);

		return;

	}