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
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>
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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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