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
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>
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libcrc32c.c
/*
* CRC32C
*@Article{castagnoli-crc,
* author = { Guy Castagnoli and Stefan Braeuer and Martin Herrman},
* title = {{Optimization of Cyclic Redundancy-Check Codes with 24
* and 32 Parity Bits}},
* journal = IEEE Transactions on Communication,
* year = {1993},
* volume = {41},
* number = {6},
* pages = {},
* month = {June},
*}
* Used by the iSCSI driver, possibly others, and derived from the
* the iscsi-crc.c module of the linux-iscsi driver at
* http://linux-iscsi.sourceforge.net.
*
* Following the example of lib/crc32, this function is intended to be
* flexible and useful for all users. Modules that currently have their
* own crc32c, but hopefully may be able to use this one are:
* net/sctp (please add all your doco to here if you change to
* use this one!)
* <endoflist>
*
* Copyright (c) 2004 Cisco Systems, Inc.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version.
*
*/
#include <crypto/hash.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/crc32c.h>
static struct crypto_shash *tfm;
u32 crc32c(u32 crc, const void *address, unsigned int length)
{
SHASH_DESC_ON_STACK(shash, tfm);
u32 ret, *ctx = (u32 *)shash_desc_ctx(shash);
int err;
shash->tfm = tfm;
shash->flags = 0;
*ctx = crc;
err = crypto_shash_update(shash, address, length);
BUG_ON(err);
ret = *ctx;
barrier_data(ctx);
return ret;
}
EXPORT_SYMBOL(crc32c);
static int __init libcrc32c_mod_init(void)
{
tfm = crypto_alloc_shash("crc32c", 0, 0);
return PTR_ERR_OR_ZERO(tfm);
}
static void __exit libcrc32c_mod_fini(void)
{
crypto_free_shash(tfm);
}
module_init(libcrc32c_mod_init);
module_exit(libcrc32c_mod_fini);
MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations");
MODULE_LICENSE("GPL");
MODULE_SOFTDEP("pre: crc32c");
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