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Revision f6ba488073fe8159851fe398cc3c5ee383bb4c7a authored by Vladimir Davydov on 18 August 2017, 22:16:08 UTC, committed by Linus Torvalds on 18 August 2017, 22:32:01 UTC 
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>
1 parent 3010f87
Raw File
crc-t10dif.c 
/*
 * T10 Data Integrity Field CRC16 calculation
 *
 * Copyright (c) 2007 Oracle Corporation.  All rights reserved.
 * Written by Martin K. Petersen <martin.petersen@oracle.com>
 *
 * This source code is licensed under the GNU General Public License,
 * Version 2. See the file COPYING for more details.
 */

#include <linux/types.h>
#include <linux/module.h>
#include <linux/crc-t10dif.h>
#include <linux/err.h>
#include <linux/init.h>
#include <crypto/hash.h>
#include <linux/static_key.h>

static struct crypto_shash *crct10dif_tfm;
static struct static_key crct10dif_fallback __read_mostly;

__u16 crc_t10dif_update(__u16 crc, const unsigned char *buffer, size_t len)
{
	struct {
		struct shash_desc shash;
		char ctx[2];
	} desc;
	int err;

	if (static_key_false(&crct10dif_fallback))
		return crc_t10dif_generic(crc, buffer, len);

	desc.shash.tfm = crct10dif_tfm;
	desc.shash.flags = 0;
	*(__u16 *)desc.ctx = crc;

	err = crypto_shash_update(&desc.shash, buffer, len);
	BUG_ON(err);

	return *(__u16 *)desc.ctx;
}
EXPORT_SYMBOL(crc_t10dif_update);

__u16 crc_t10dif(const unsigned char *buffer, size_t len)
{
	return crc_t10dif_update(0, buffer, len);
}
EXPORT_SYMBOL(crc_t10dif);

static int __init crc_t10dif_mod_init(void)
{
	crct10dif_tfm = crypto_alloc_shash("crct10dif", 0, 0);
	if (IS_ERR(crct10dif_tfm)) {
		static_key_slow_inc(&crct10dif_fallback);
		crct10dif_tfm = NULL;
	}
	return 0;
}

static void __exit crc_t10dif_mod_fini(void)
{
	crypto_free_shash(crct10dif_tfm);
}

module_init(crc_t10dif_mod_init);
module_exit(crc_t10dif_mod_fini);

MODULE_DESCRIPTION("T10 DIF CRC calculation");
MODULE_LICENSE("GPL");
MODULE_SOFTDEP("pre: crct10dif");
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