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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uuid.c
/*
* Unified UUID/GUID definition
*
* Copyright (C) 2009, 2016 Intel Corp.
* Huang Ying <ying.huang@intel.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version
* 2 as published by the Free Software Foundation;
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <linux/kernel.h>
#include <linux/ctype.h>
#include <linux/errno.h>
#include <linux/export.h>
#include <linux/uuid.h>
#include <linux/random.h>
const guid_t guid_null;
EXPORT_SYMBOL(guid_null);
const uuid_t uuid_null;
EXPORT_SYMBOL(uuid_null);
const u8 guid_index[16] = {3,2,1,0,5,4,7,6,8,9,10,11,12,13,14,15};
const u8 uuid_index[16] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
/***************************************************************
* Random UUID interface
*
* Used here for a Boot ID, but can be useful for other kernel
* drivers.
***************************************************************/
/*
* Generate random UUID
*/
void generate_random_uuid(unsigned char uuid[16])
{
get_random_bytes(uuid, 16);
/* Set UUID version to 4 --- truly random generation */
uuid[6] = (uuid[6] & 0x0F) | 0x40;
/* Set the UUID variant to DCE */
uuid[8] = (uuid[8] & 0x3F) | 0x80;
}
EXPORT_SYMBOL(generate_random_uuid);
static void __uuid_gen_common(__u8 b[16])
{
prandom_bytes(b, 16);
/* reversion 0b10 */
b[8] = (b[8] & 0x3F) | 0x80;
}
void guid_gen(guid_t *lu)
{
__uuid_gen_common(lu->b);
/* version 4 : random generation */
lu->b[7] = (lu->b[7] & 0x0F) | 0x40;
}
EXPORT_SYMBOL_GPL(guid_gen);
void uuid_gen(uuid_t *bu)
{
__uuid_gen_common(bu->b);
/* version 4 : random generation */
bu->b[6] = (bu->b[6] & 0x0F) | 0x40;
}
EXPORT_SYMBOL_GPL(uuid_gen);
/**
* uuid_is_valid - checks if UUID string valid
* @uuid: UUID string to check
*
* Description:
* It checks if the UUID string is following the format:
* xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
* where x is a hex digit.
*
* Return: true if input is valid UUID string.
*/
bool uuid_is_valid(const char *uuid)
{
unsigned int i;
for (i = 0; i < UUID_STRING_LEN; i++) {
if (i == 8 || i == 13 || i == 18 || i == 23) {
if (uuid[i] != '-')
return false;
} else if (!isxdigit(uuid[i])) {
return false;
}
}
return true;
}
EXPORT_SYMBOL(uuid_is_valid);
static int __uuid_parse(const char *uuid, __u8 b[16], const u8 ei[16])
{
static const u8 si[16] = {0,2,4,6,9,11,14,16,19,21,24,26,28,30,32,34};
unsigned int i;
if (!uuid_is_valid(uuid))
return -EINVAL;
for (i = 0; i < 16; i++) {
int hi = hex_to_bin(uuid[si[i] + 0]);
int lo = hex_to_bin(uuid[si[i] + 1]);
b[ei[i]] = (hi << 4) | lo;
}
return 0;
}
int guid_parse(const char *uuid, guid_t *u)
{
return __uuid_parse(uuid, u->b, guid_index);
}
EXPORT_SYMBOL(guid_parse);
int uuid_parse(const char *uuid, uuid_t *u)
{
return __uuid_parse(uuid, u->b, uuid_index);
}
EXPORT_SYMBOL(uuid_parse);
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