On Wed, Jun 19, 2019 at 04:52:53PM -0400, Qian Cai wrote: > 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); Ah, perfect catch! Thank you, Qian! Acked-by: Roman Gushchin <guro@xxxxxx>
