From: Feng Tang feng.tang@intel.com
[ Upstream commit d71608a877362becdc94191f190902fac1e64d35 ]
When doing slub_debug test, kfence's 'test_memcache_typesafe_by_rcu' kunit test case cause a use-after-free error:
BUG: KASAN: use-after-free in kobject_del+0x14/0x30 Read of size 8 at addr ffff888007679090 by task kunit_try_catch/261
CPU: 1 PID: 261 Comm: kunit_try_catch Tainted: G B N 6.0.0-rc5-next-20220916 #17 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x34/0x48 print_address_description.constprop.0+0x87/0x2a5 print_report+0x103/0x1ed kasan_report+0xb7/0x140 kobject_del+0x14/0x30 kmem_cache_destroy+0x130/0x170 test_exit+0x1a/0x30 kunit_try_run_case+0xad/0xc0 kunit_generic_run_threadfn_adapter+0x26/0x50 kthread+0x17b/0x1b0 </TASK>
The cause is inside kmem_cache_destroy():
kmem_cache_destroy acquire lock/mutex shutdown_cache schedule_work(kmem_cache_release) (if RCU flag set) release lock/mutex kmem_cache_release (if RCU flag not set)
In some certain timing, the scheduled work could be run before the next RCU flag checking, which can then get a wrong value and lead to double kmem_cache_release().
Fix it by caching the RCU flag inside protected area, just like 'refcnt'
Fixes: 0495e337b703 ("mm/slab_common: Deleting kobject in kmem_cache_destroy() without holding slab_mutex/cpu_hotplug_lock") Signed-off-by: Feng Tang feng.tang@intel.com Reviewed-by: Hyeonggon Yoo 42.hyeyoo@gmail.com Reviewed-by: Waiman Long longman@redhat.com Signed-off-by: Vlastimil Babka vbabka@suse.cz Signed-off-by: Sasha Levin sashal@kernel.org --- mm/slab_common.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/mm/slab_common.c b/mm/slab_common.c index dbd4b6f9b0e7..29ae1358d5f0 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -503,6 +503,7 @@ void slab_kmem_cache_release(struct kmem_cache *s) void kmem_cache_destroy(struct kmem_cache *s) { int refcnt; + bool rcu_set;
if (unlikely(!s) || !kasan_check_byte(s)) return; @@ -510,6 +511,8 @@ void kmem_cache_destroy(struct kmem_cache *s) cpus_read_lock(); mutex_lock(&slab_mutex);
+ rcu_set = s->flags & SLAB_TYPESAFE_BY_RCU; + refcnt = --s->refcount; if (refcnt) goto out_unlock; @@ -520,7 +523,7 @@ void kmem_cache_destroy(struct kmem_cache *s) out_unlock: mutex_unlock(&slab_mutex); cpus_read_unlock(); - if (!refcnt && !(s->flags & SLAB_TYPESAFE_BY_RCU)) + if (!refcnt && !rcu_set) kmem_cache_release(s); } EXPORT_SYMBOL(kmem_cache_destroy);