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Revision d38a2b7a9c939e6d7329ab92b96559ccebf7b135 authored by Muchun Song on 24 July 2020, 04:15:27 UTC, committed by Linus Torvalds on 24 July 2020, 19:42:41 UTC 
mm: memcg/slab: fix memory leak at non-root kmem_cache destroy
 
If the kmem_cache refcount is greater than one, we should not mark the
root kmem_cache as dying.  If we mark the root kmem_cache dying
incorrectly, the non-root kmem_cache can never be destroyed.  It
resulted in memory leak when memcg was destroyed.  We can use the
following steps to reproduce.

  1) Use kmem_cache_create() to create a new kmem_cache named A.
  2) Coincidentally, the kmem_cache A is an alias for kmem_cache B,
     so the refcount of B is just increased.
  3) Use kmem_cache_destroy() to destroy the kmem_cache A, just
     decrease the B's refcount but mark the B as dying.
  4) Create a new memory cgroup and alloc memory from the kmem_cache
     B. It leads to create a non-root kmem_cache for allocating memory.
  5) When destroy the memory cgroup created in the step 4), the
     non-root kmem_cache can never be destroyed.

If we repeat steps 4) and 5), this will cause a lot of memory leak.  So
only when refcount reach zero, we mark the root kmem_cache as dying.

Fixes: 92ee383f6daa ("mm: fix race between kmem_cache destroy, create and deactivate")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20200716165103.83462-1-songmuchun@bytedance.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 8d22a93
Raw File
fips.c 
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * FIPS 200 support.
 *
 * Copyright (c) 2008 Neil Horman <nhorman@tuxdriver.com>
 */

#include <linux/export.h>
#include <linux/fips.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sysctl.h>
#include <linux/notifier.h>

int fips_enabled;
EXPORT_SYMBOL_GPL(fips_enabled);

ATOMIC_NOTIFIER_HEAD(fips_fail_notif_chain);
EXPORT_SYMBOL_GPL(fips_fail_notif_chain);

/* Process kernel command-line parameter at boot time. fips=0 or fips=1 */
static int fips_enable(char *str)
{
	fips_enabled = !!simple_strtol(str, NULL, 0);
	printk(KERN_INFO "fips mode: %s\n",
		fips_enabled ? "enabled" : "disabled");
	return 1;
}

__setup("fips=", fips_enable);

static struct ctl_table crypto_sysctl_table[] = {
	{
		.procname       = "fips_enabled",
		.data           = &fips_enabled,
		.maxlen         = sizeof(int),
		.mode           = 0444,
		.proc_handler   = proc_dointvec
	},
	{}
};

static struct ctl_table crypto_dir_table[] = {
	{
		.procname       = "crypto",
		.mode           = 0555,
		.child          = crypto_sysctl_table
	},
	{}
};

static struct ctl_table_header *crypto_sysctls;

static void crypto_proc_fips_init(void)
{
	crypto_sysctls = register_sysctl_table(crypto_dir_table);
}

static void crypto_proc_fips_exit(void)
{
	unregister_sysctl_table(crypto_sysctls);
}

void fips_fail_notify(void)
{
	if (fips_enabled)
		atomic_notifier_call_chain(&fips_fail_notif_chain, 0, NULL);
}
EXPORT_SYMBOL_GPL(fips_fail_notify);

static int __init fips_init(void)
{
	crypto_proc_fips_init();
	return 0;
}

static void __exit fips_exit(void)
{
	crypto_proc_fips_exit();
}

subsys_initcall(fips_init);
module_exit(fips_exit);
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