Revision 35a9393c95b31870a74f51a3e7455f33f5657b6f authored by Peter Zijlstra on 26 February 2015, 15:23:11 UTC, committed by Ingo Molnar on 23 March 2015, 09:49:07 UTC
Module unload calls lockdep_free_key_range(), which removes entries
from the data structures. Most of the lockdep code OTOH assumes the
data structures are append only; in specific see the comments in
add_lock_to_list() and look_up_lock_class().

Clearly this has only worked by accident; make it work proper. The
actual scenario to make it go boom would involve the memory freed by
the module unlock being re-allocated and re-used for a lock inside of
a rcu-sched grace period. This is a very unlikely scenario, still
better plug the hole.

Use RCU list iteration in all places and ammend the comments.

Change lockdep_free_key_range() to issue a sync_sched() between
removal from the lists and returning -- which results in the memory
being freed. Further ensure the callers are placed correctly and
comment the requirements.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Tsyvarev <tsyvarev@ispras.ru>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
1 parent bc465aa
Raw File
lz4hc.c
/*
 * Cryptographic API.
 *
 * Copyright (c) 2013 Chanho Min <chanho.min@lge.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.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 51
 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 *
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/crypto.h>
#include <linux/vmalloc.h>
#include <linux/lz4.h>

struct lz4hc_ctx {
	void *lz4hc_comp_mem;
};

static int lz4hc_init(struct crypto_tfm *tfm)
{
	struct lz4hc_ctx *ctx = crypto_tfm_ctx(tfm);

	ctx->lz4hc_comp_mem = vmalloc(LZ4HC_MEM_COMPRESS);
	if (!ctx->lz4hc_comp_mem)
		return -ENOMEM;

	return 0;
}

static void lz4hc_exit(struct crypto_tfm *tfm)
{
	struct lz4hc_ctx *ctx = crypto_tfm_ctx(tfm);

	vfree(ctx->lz4hc_comp_mem);
}

static int lz4hc_compress_crypto(struct crypto_tfm *tfm, const u8 *src,
			    unsigned int slen, u8 *dst, unsigned int *dlen)
{
	struct lz4hc_ctx *ctx = crypto_tfm_ctx(tfm);
	size_t tmp_len = *dlen;
	int err;

	err = lz4hc_compress(src, slen, dst, &tmp_len, ctx->lz4hc_comp_mem);

	if (err < 0)
		return -EINVAL;

	*dlen = tmp_len;
	return 0;
}

static int lz4hc_decompress_crypto(struct crypto_tfm *tfm, const u8 *src,
			      unsigned int slen, u8 *dst, unsigned int *dlen)
{
	int err;
	size_t tmp_len = *dlen;
	size_t __slen = slen;

	err = lz4_decompress_unknownoutputsize(src, __slen, dst, &tmp_len);
	if (err < 0)
		return -EINVAL;

	*dlen = tmp_len;
	return err;
}

static struct crypto_alg alg_lz4hc = {
	.cra_name		= "lz4hc",
	.cra_flags		= CRYPTO_ALG_TYPE_COMPRESS,
	.cra_ctxsize		= sizeof(struct lz4hc_ctx),
	.cra_module		= THIS_MODULE,
	.cra_list		= LIST_HEAD_INIT(alg_lz4hc.cra_list),
	.cra_init		= lz4hc_init,
	.cra_exit		= lz4hc_exit,
	.cra_u			= { .compress = {
	.coa_compress		= lz4hc_compress_crypto,
	.coa_decompress		= lz4hc_decompress_crypto } }
};

static int __init lz4hc_mod_init(void)
{
	return crypto_register_alg(&alg_lz4hc);
}

static void __exit lz4hc_mod_fini(void)
{
	crypto_unregister_alg(&alg_lz4hc);
}

module_init(lz4hc_mod_init);
module_exit(lz4hc_mod_fini);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("LZ4HC Compression Algorithm");
MODULE_ALIAS_CRYPTO("lz4hc");
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