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mm/slab_common: fix possible double free of kmem_cache

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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: 0495e337b7 ("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>
This commit is contained in:
Feng Tang 2022-09-19 11:12:41 +08:00 committed by Vlastimil Babka
parent 5373b8a09d
commit d71608a877
1 changed files with 4 additions and 1 deletions
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5
mm/slab_common.c
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@ -475,6 +475,7 @@ 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;
@ -482,6 +483,8 @@ 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;
@ -492,7 +495,7 @@ 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);