On Thu, Jun 29, 2017 at 11:04:01AM -0700, Andrei Vagin wrote:
> Hello,
>
> We run CRIU tests on the linus' tree and found that kmemleak reports
> unreferenced objects which are allocated from memcg_create_kmem_cache:
>
> unreferenced object 0xffff9f79442cd980 (size 112):
> comm "kworker/1:4", pid 15416, jiffies 4307432421 (age 28687.562s)
> hex dump (first 32 bytes):
> 00 00 00 00 ad 4e ad de ff ff ff ff 00 00 00 00 .....N..........
> ff ff ff ff ff ff ff ff b8 39 1b 97 ff ff ff ff .........9......
> backtrace:
> [<ffffffff9591d28a>] kmemleak_alloc+0x4a/0xa0
> [<ffffffff95276198>] kmem_cache_alloc_node+0x168/0x2a0
> [<ffffffff95279f28>] __kmem_cache_create+0x2b8/0x5c0
> [<ffffffff9522ff57>] create_cache+0xb7/0x1e0
> [<ffffffff952305f8>] memcg_create_kmem_cache+0x118/0x160
> [<ffffffff9528eaf0>] memcg_kmem_cache_create_func+0x20/0x110
> [<ffffffff950cd6c5>] process_one_work+0x205/0x5d0
> [<ffffffff950cdade>] worker_thread+0x4e/0x3a0
> [<ffffffff950d5169>] kthread+0x109/0x140
> [<ffffffff9592b8fa>] ret_from_fork+0x2a/0x40
> [<ffffffffffffffff>] 0xffffffffffffffff
> 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:
> [<ffffffff9591d28a>] kmemleak_alloc+0x4a/0xa0
> [<ffffffff9527a378>] __kmalloc_track_caller+0x148/0x2c0
> [<ffffffff95499466>] kvasprintf+0x66/0xd0
> [<ffffffff954995a9>] kasprintf+0x49/0x70
> [<ffffffff952305c6>] memcg_create_kmem_cache+0xe6/0x160
> [<ffffffff9528eaf0>] memcg_kmem_cache_create_func+0x20/0x110
> [<ffffffff950cd6c5>] process_one_work+0x205/0x5d0
> [<ffffffff950cdade>] worker_thread+0x4e/0x3a0
> [<ffffffff950d5169>] kthread+0x109/0x140
> [<ffffffff9592b8fa>] ret_from_fork+0x2a/0x40
> [<ffffffffffffffff>] 0xffffffffffffffff
> 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:
> [<ffffffff9591d28a>] kmemleak_alloc+0x4a/0xa0
> [<ffffffff95275bc8>] kmem_cache_alloc+0x128/0x280
> [<ffffffff9522fedb>] create_cache+0x3b/0x1e0
> [<ffffffff952305f8>] memcg_create_kmem_cache+0x118/0x160
> [<ffffffff9528eaf0>] memcg_kmem_cache_create_func+0x20/0x110
> [<ffffffff950cd6c5>] process_one_work+0x205/0x5d0
> [<ffffffff950cdade>] worker_thread+0x4e/0x3a0
> [<ffffffff950d5169>] kthread+0x109/0x140
> [<ffffffff9592b8fa>] ret_from_fork+0x2a/0x40
> [<ffffffffffffffff>] 0xffffffffffffffff
> unreferenced object 0xffff9f798cac8000 (size 1024):
> comm "kworker/1:4", pid 15416, jiffies 4307432429 (age 28687.573s)
> hex dump (first 32 bytes):
> 10 00 00 00 70 09 00 00 20 09 00 00 00 09 00 00 ....p... .......
> 80 02 00 00 b0 03 00 00 30 06 00 00 50 02 00 00 ........0...P...
> backtrace:
> [<ffffffff9591d28a>] kmemleak_alloc+0x4a/0xa0
> [<ffffffff952766b8>] __kmalloc+0x158/0x2c0
> [<ffffffff95230a5f>] cache_random_seq_create+0x6f/0x130
> [<ffffffff952714da>] init_cache_random_seq+0x3a/0x90
> [<ffffffff95279d70>] __kmem_cache_create+0x100/0x5c0
> [<ffffffff9522ff57>] create_cache+0xb7/0x1e0
> [<ffffffff952305f8>] memcg_create_kmem_cache+0x118/0x160
> [<ffffffff9528eaf0>] memcg_kmem_cache_create_func+0x20/0x110
> [<ffffffff950cd6c5>] process_one_work+0x205/0x5d0
> [<ffffffff950cdade>] worker_thread+0x4e/0x3a0
> [<ffffffff950d5169>] kthread+0x109/0x140
> [<ffffffff9592b8fa>] ret_from_fork+0x2a/0x40
> [<ffffffffffffffff>] 0xffffffffffffffff
> unreferenced object 0xffff9f79442cd800 (size 112):
>
> [root@zdtm linux]# git describe HEAD
> v4.12-rc7-26-gb216759
>
> [root@zdtm linux]# uname -a
> Linux zdtm.openvz.org 4.12.0-rc7+ #9 SMP Thu Jun 29 08:28:18 CEST 2017
> x86_64 x86_64 x86_64 GNU/Linux
Could you check if the patch below fixes the issue?
--
From: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Subject: [PATCH] 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:
[<ffffffff9591d28a>] kmemleak_alloc+0x4a/0xa0
[<ffffffff9527a378>] __kmalloc_track_caller+0x148/0x2c0
[<ffffffff95499466>] kvasprintf+0x66/0xd0
[<ffffffff954995a9>] kasprintf+0x49/0x70
[<ffffffff952305c6>] memcg_create_kmem_cache+0xe6/0x160
[<ffffffff9528eaf0>] memcg_kmem_cache_create_func+0x20/0x110
[<ffffffff950cd6c5>] process_one_work+0x205/0x5d0
[<ffffffff950cdade>] worker_thread+0x4e/0x3a0
[<ffffffff950d5169>] kthread+0x109/0x140
[<ffffffff9592b8fa>] ret_from_fork+0x2a/0x40
[<ffffffffffffffff>] 0xffffffffffffffff
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:
[<ffffffff9591d28a>] kmemleak_alloc+0x4a/0xa0
[<ffffffff95275bc8>] kmem_cache_alloc+0x128/0x280
[<ffffffff9522fedb>] create_cache+0x3b/0x1e0
[<ffffffff952305f8>] memcg_create_kmem_cache+0x118/0x160
[<ffffffff9528eaf0>] memcg_kmem_cache_create_func+0x20/0x110
[<ffffffff950cd6c5>] process_one_work+0x205/0x5d0
[<ffffffff950cdade>] worker_thread+0x4e/0x3a0
[<ffffffff950d5169>] kthread+0x109/0x140
[<ffffffff9592b8fa>] ret_from_fork+0x2a/0x40
[<ffffffffffffffff>] 0xffffffffffffffff
Fix the leak by adding the missing call to kobject_put() to
sysfs_slab_remove_workfn().
Reported-by: Andrei Vagin <avagin@xxxxxxxxx>
Signed-off-by: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Fixes: 3b7b314053d02 ("slub: make sysfs file removal asynchronous")
diff --git a/mm/slub.c b/mm/slub.c
index 8addc535bcdc..a0f3c56611c6 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -5637,13 +5637,14 @@ 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);
}
--
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