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authorVladimir Davydov <vdavydov.dev@gmail.com>2017-08-18 15:16:08 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-08-18 15:32:01 -0700
commitf6ba488073fe8159851fe398cc3c5ee383bb4c7a (patch)
treeef31a6801b9ba41c586349319994cb5eaf6555b6
parent3010f876500f9ba921afaeccec30c45ca6584dc8 (diff)
downloadlinux-stericsson-f6ba488073fe8159851fe398cc3c5ee383bb4c7a.tar.gz
slub: fix per memcg cache leak on css offline
To avoid a possible deadlock, sysfs_slab_remove() schedules an asynchronous work to delete sysfs entries corresponding to the kmem cache. To ensure the cache isn't freed before the work function is called, it takes a reference to the cache kobject. The reference is supposed to be released by the work function. However, the work function (sysfs_slab_remove_workfn()) does nothing in case the cache sysfs entry has already been deleted, leaking the kobject and the corresponding cache. This may happen on a per memcg cache destruction, because sysfs entries of a per memcg cache are deleted on memcg offline if the cache is empty (see __kmemcg_cache_deactivate()). The kmemleak report looks like this: unreferenced object 0xffff9f798a79f540 (size 32): comm "kworker/1:4", pid 15416, jiffies 4307432429 (age 28687.554s) hex dump (first 32 bytes): 6b 6d 61 6c 6c 6f 63 2d 31 36 28 31 35 39 39 3a kmalloc-16(1599: 6e 65 77 72 6f 6f 74 29 00 23 6b c0 ff ff ff ff newroot).#k..... backtrace: kmemleak_alloc+0x4a/0xa0 __kmalloc_track_caller+0x148/0x2c0 kvasprintf+0x66/0xd0 kasprintf+0x49/0x70 memcg_create_kmem_cache+0xe6/0x160 memcg_kmem_cache_create_func+0x20/0x110 process_one_work+0x205/0x5d0 worker_thread+0x4e/0x3a0 kthread+0x109/0x140 ret_from_fork+0x2a/0x40 unreferenced object 0xffff9f79b6136840 (size 416): comm "kworker/1:4", pid 15416, jiffies 4307432429 (age 28687.573s) hex dump (first 32 bytes): 40 fb 80 c2 3e 33 00 00 00 00 00 40 00 00 00 00 @...>3.....@.... 00 00 00 00 00 00 00 00 10 00 00 00 10 00 00 00 ................ backtrace: kmemleak_alloc+0x4a/0xa0 kmem_cache_alloc+0x128/0x280 create_cache+0x3b/0x1e0 memcg_create_kmem_cache+0x118/0x160 memcg_kmem_cache_create_func+0x20/0x110 process_one_work+0x205/0x5d0 worker_thread+0x4e/0x3a0 kthread+0x109/0x140 ret_from_fork+0x2a/0x40 Fix the leak by adding the missing call to kobject_put() to sysfs_slab_remove_workfn(). Link: http://lkml.kernel.org/r/20170812181134.25027-1-vdavydov.dev@gmail.com Fixes: 3b7b314053d02 ("slub: make sysfs file removal asynchronous") Signed-off-by: Vladimir Davydov <vdavydov.dev@gmail.com> Reported-by: Andrei Vagin <avagin@gmail.com> Tested-by: Andrei Vagin <avagin@gmail.com> Acked-by: Tejun Heo <tj@kernel.org> Acked-by: David Rientjes <rientjes@google.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: <stable@vger.kernel.org> [4.12.x] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/slub.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/mm/slub.c b/mm/slub.c
index 1d3f9835f4ea..e8b4e31162ca 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5642,13 +5642,14 @@ static void sysfs_slab_remove_workfn(struct work_struct *work)
* A cache is never shut down before deactivation is
* complete, so no need to worry about synchronization.
*/
- return;
+ goto out;
#ifdef CONFIG_MEMCG
kset_unregister(s->memcg_kset);
#endif
kobject_uevent(&s->kobj, KOBJ_REMOVE);
kobject_del(&s->kobj);
+out:
kobject_put(&s->kobj);
}