From: Muchun Song <songmuchun@xxxxxxxxxxxxx> 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@xxxxxxxxxx/ [1] Reported-by: syzbot+f8c45ccc7d5d45fc5965@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: d3fb45f370d9 ("mm, kfence: insert KFENCE hooks for SLAB") Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Marco Elver <elver@xxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/slab.c | 1 + 1 file changed, 1 insertion(+) --- a/mm/slab.c +++ b/mm/slab.c @@ -3421,6 +3421,7 @@ 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; }
