The linux-next commit "mm: rework non-root kmem_cache lifecycle management" [1] introduced an use-after-free below because kmemcg_workfn() may call slab_kmem_cache_release() which has already freed the whole kmem_cache. Fix it by removing the bogus NULL assignment and checkings that will not work with SLUB_DEBUG poisoning anyway. [1] https://lore.kernel.org/patchwork/patch/1087376/ BUG kmem_cache (Tainted: G B W ): Poison overwritten INFO: 0x(____ptrval____)-0x(____ptrval____). First byte 0x0 instead of 0x6b INFO: Allocated in create_cache+0x6c/0x1bc age=2653 cpu=154 pid=1599 kmem_cache_alloc+0x514/0x568 create_cache+0x6c/0x1bc memcg_create_kmem_cache+0xfc/0x11c memcg_kmem_cache_create_func+0x40/0x170 process_one_work+0x4e0/0xa54 worker_thread+0x498/0x650 kthread+0x1b8/0x1d4 ret_from_fork+0x10/0x18 INFO: Freed in slab_kmem_cache_release+0x3c/0x48 age=255 cpu=7 pid=1505 slab_kmem_cache_release+0x3c/0x48 kmem_cache_release+0x1c/0x28 kobject_cleanup+0x134/0x288 kobject_put+0x5c/0x68 sysfs_slab_release+0x2c/0x38 shutdown_cache+0x190/0x234 kmemcg_cache_shutdown_fn+0x1c/0x34 kmemcg_workfn+0x44/0x68 process_one_work+0x4e0/0xa54 worker_thread+0x498/0x650 kthread+0x1b8/0x1d4 ret_from_fork+0x10/0x18 INFO: Slab 0x(____ptrval____) objects=64 used=64 fp=0x(____ptrval____) flags=0x17ffffffc000200 INFO: Object 0x(____ptrval____) @offset=11601272640106456192 fp=0x(____ptrval____) Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................ Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................ Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................ Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................ Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................ Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................ Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................ Redzone (____ptrval____): bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb ................ Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 00 00 00 00 00 00 00 00 kkkkkkkk........ Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object (____ptrval____): 6b 6b 6b 6b 6b 6b 6b a5 kkkkkkk. Redzone (____ptrval____): bb bb bb bb bb bb bb bb ........ Padding (____ptrval____): 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ Padding (____ptrval____): 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ Padding (____ptrval____): 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ Padding (____ptrval____): 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ Padding (____ptrval____): 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZ CPU: 193 PID: 1557 Comm: kworker/193:1 Tainted: G B W 5.2.0-rc5-next-20190619+ #8 Hardware name: HPE Apollo 70 /C01_APACHE_MB , BIOS L50_5.13_1.0.9 03/01/2019 Workqueue: memcg_kmem_cache memcg_kmem_cache_create_func Call trace: dump_backtrace+0x0/0x268 show_stack+0x20/0x2c dump_stack+0xb4/0x108 print_trailer+0x274/0x298 check_bytes_and_report+0xc4/0x118 check_object+0x2fc/0x36c alloc_debug_processing+0x154/0x240 ___slab_alloc+0x710/0xa68 kmem_cache_alloc+0x514/0x568 create_cache+0x6c/0x1bc memcg_create_kmem_cache+0xfc/0x11c memcg_kmem_cache_create_func+0x40/0x170 process_one_work+0x4e0/0xa54 worker_thread+0x498/0x650 kthread+0x1b8/0x1d4 ret_from_fork+0x10/0x18 FIX kmem_cache: Restoring 0x(____ptrval____)-0x(____ptrval____)=0x6b FIX kmem_cache: Marking all objects used Signed-off-by: Qian Cai <cai@xxxxxx> --- mm/slab_common.c | 5 ----- 1 file changed, 5 deletions(-) diff --git a/mm/slab_common.c b/mm/slab_common.c index 91e8c739dc97..bb8aec6d8744 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -714,10 +714,7 @@ static void kmemcg_workfn(struct work_struct *work) get_online_mems(); mutex_lock(&slab_mutex); - s->memcg_params.work_fn(s); - s->memcg_params.work_fn = NULL; - mutex_unlock(&slab_mutex); put_online_mems(); @@ -753,7 +750,6 @@ static void kmemcg_cache_shutdown(struct percpu_ref *percpu_ref) if (s->memcg_params.root_cache->memcg_params.dying) goto unlock; - WARN_ON(s->memcg_params.work_fn); s->memcg_params.work_fn = kmemcg_cache_shutdown_fn; INIT_WORK(&s->memcg_params.work, kmemcg_workfn); queue_work(memcg_kmem_cache_wq, &s->memcg_params.work); @@ -784,7 +780,6 @@ static void kmemcg_cache_deactivate(struct kmem_cache *s) if (s->memcg_params.root_cache->memcg_params.dying) goto unlock; - WARN_ON_ONCE(s->memcg_params.work_fn); s->memcg_params.work_fn = kmemcg_cache_deactivate_after_rcu; call_rcu(&s->memcg_params.rcu_head, kmemcg_rcufn); unlock: -- 1.8.3.1
