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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
ecb.c 
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * ECB: Electronic CodeBook mode
 *
 * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
 */

#include <crypto/algapi.h>
#include <crypto/internal/skcipher.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

static int crypto_ecb_crypt(struct skcipher_request *req,
			    struct crypto_cipher *cipher,
			    void (*fn)(struct crypto_tfm *, u8 *, const u8 *))
{
	const unsigned int bsize = crypto_cipher_blocksize(cipher);
	struct skcipher_walk walk;
	unsigned int nbytes;
	int err;

	err = skcipher_walk_virt(&walk, req, false);

	while ((nbytes = walk.nbytes) != 0) {
		const u8 *src = walk.src.virt.addr;
		u8 *dst = walk.dst.virt.addr;

		do {
			fn(crypto_cipher_tfm(cipher), dst, src);

			src += bsize;
			dst += bsize;
		} while ((nbytes -= bsize) >= bsize);

		err = skcipher_walk_done(&walk, nbytes);
	}

	return err;
}

static int crypto_ecb_encrypt(struct skcipher_request *req)
{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);

	return crypto_ecb_crypt(req, cipher,
				crypto_cipher_alg(cipher)->cia_encrypt);
}

static int crypto_ecb_decrypt(struct skcipher_request *req)
{
	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
	struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);

	return crypto_ecb_crypt(req, cipher,
				crypto_cipher_alg(cipher)->cia_decrypt);
}

static int crypto_ecb_create(struct crypto_template *tmpl, struct rtattr **tb)
{
	struct skcipher_instance *inst;
	int err;

	inst = skcipher_alloc_instance_simple(tmpl, tb);
	if (IS_ERR(inst))
		return PTR_ERR(inst);

	inst->alg.ivsize = 0; /* ECB mode doesn't take an IV */

	inst->alg.encrypt = crypto_ecb_encrypt;
	inst->alg.decrypt = crypto_ecb_decrypt;

	err = skcipher_register_instance(tmpl, inst);
	if (err)
		inst->free(inst);

	return err;
}

static struct crypto_template crypto_ecb_tmpl = {
	.name = "ecb",
	.create = crypto_ecb_create,
	.module = THIS_MODULE,
};

static int __init crypto_ecb_module_init(void)
{
	return crypto_register_template(&crypto_ecb_tmpl);
}

static void __exit crypto_ecb_module_exit(void)
{
	crypto_unregister_template(&crypto_ecb_tmpl);
}

subsys_initcall(crypto_ecb_module_init);
module_exit(crypto_ecb_module_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("ECB block cipher mode of operation");
MODULE_ALIAS_CRYPTO("ecb");
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