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; }