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Revision a318f12ed8843cfac53198390c74a565c632f417 authored by Kees Cook on 16 July 2019, 23:30:21 UTC, committed by Linus Torvalds on 17 July 2019, 02:23:24 UTC 
ipc/mqueue.c: only perform resource calculation if user valid
 
Andreas Christoforou reported:

  UBSAN: Undefined behaviour in ipc/mqueue.c:414:49 signed integer overflow:
  9 * 2305843009213693951 cannot be represented in type 'long int'
  ...
  Call Trace:
    mqueue_evict_inode+0x8e7/0xa10 ipc/mqueue.c:414
    evict+0x472/0x8c0 fs/inode.c:558
    iput_final fs/inode.c:1547 [inline]
    iput+0x51d/0x8c0 fs/inode.c:1573
    mqueue_get_inode+0x8eb/0x1070 ipc/mqueue.c:320
    mqueue_create_attr+0x198/0x440 ipc/mqueue.c:459
    vfs_mkobj+0x39e/0x580 fs/namei.c:2892
    prepare_open ipc/mqueue.c:731 [inline]
    do_mq_open+0x6da/0x8e0 ipc/mqueue.c:771

Which could be triggered by:

        struct mq_attr attr = {
                .mq_flags = 0,
                .mq_maxmsg = 9,
                .mq_msgsize = 0x1fffffffffffffff,
                .mq_curmsgs = 0,
        };

        if (mq_open("/testing", 0x40, 3, &attr) == (mqd_t) -1)
                perror("mq_open");

mqueue_get_inode() was correctly rejecting the giant mq_msgsize, and
preparing to return -EINVAL.  During the cleanup, it calls
mqueue_evict_inode() which performed resource usage tracking math for
updating "user", before checking if there was a valid "user" at all
(which would indicate that the calculations would be sane).  Instead,
delay this check to after seeing a valid "user".

The overflow was real, but the results went unused, so while the flaw is
harmless, it's noisy for kernel fuzzers, so just fix it by moving the
calculation under the non-NULL "user" where it actually gets used.

Link: http://lkml.kernel.org/r/201906072207.ECB65450@keescook
Signed-off-by: Kees Cook <keescook@chromium.org>
Reported-by: Andreas Christoforou <andreaschristofo@gmail.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 6b15f67
Raw File
lz4hc.c 
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Cryptographic API.
 *
 * Copyright (c) 2013 Chanho Min <chanho.min@lge.com>
 */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/crypto.h>
#include <linux/vmalloc.h>
#include <linux/lz4.h>
#include <crypto/internal/scompress.h>

struct lz4hc_ctx {
	void *lz4hc_comp_mem;
};

static void *lz4hc_alloc_ctx(struct crypto_scomp *tfm)
{
	void *ctx;

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

	return ctx;
}

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

	ctx->lz4hc_comp_mem = lz4hc_alloc_ctx(NULL);
	if (IS_ERR(ctx->lz4hc_comp_mem))
		return -ENOMEM;

	return 0;
}

static void lz4hc_free_ctx(struct crypto_scomp *tfm, void *ctx)
{
	vfree(ctx);
}

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

	lz4hc_free_ctx(NULL, ctx->lz4hc_comp_mem);
}

static int __lz4hc_compress_crypto(const u8 *src, unsigned int slen,
				   u8 *dst, unsigned int *dlen, void *ctx)
{
	int out_len = LZ4_compress_HC(src, dst, slen,
		*dlen, LZ4HC_DEFAULT_CLEVEL, ctx);

	if (!out_len)
		return -EINVAL;

	*dlen = out_len;
	return 0;
}

static int lz4hc_scompress(struct crypto_scomp *tfm, const u8 *src,
			   unsigned int slen, u8 *dst, unsigned int *dlen,
			   void *ctx)
{
	return __lz4hc_compress_crypto(src, slen, dst, dlen, ctx);
}

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);

	return __lz4hc_compress_crypto(src, slen, dst, dlen,
					ctx->lz4hc_comp_mem);
}

static int __lz4hc_decompress_crypto(const u8 *src, unsigned int slen,
				     u8 *dst, unsigned int *dlen, void *ctx)
{
	int out_len = LZ4_decompress_safe(src, dst, slen, *dlen);

	if (out_len < 0)
		return -EINVAL;

	*dlen = out_len;
	return 0;
}

static int lz4hc_sdecompress(struct crypto_scomp *tfm, const u8 *src,
			     unsigned int slen, u8 *dst, unsigned int *dlen,
			     void *ctx)
{
	return __lz4hc_decompress_crypto(src, slen, dst, dlen, NULL);
}

static int lz4hc_decompress_crypto(struct crypto_tfm *tfm, const u8 *src,
				   unsigned int slen, u8 *dst,
				   unsigned int *dlen)
{
	return __lz4hc_decompress_crypto(src, slen, dst, dlen, NULL);
}

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

static struct scomp_alg scomp = {
	.alloc_ctx		= lz4hc_alloc_ctx,
	.free_ctx		= lz4hc_free_ctx,
	.compress		= lz4hc_scompress,
	.decompress		= lz4hc_sdecompress,
	.base			= {
		.cra_name	= "lz4hc",
		.cra_driver_name = "lz4hc-scomp",
		.cra_module	 = THIS_MODULE,
	}
};

static int __init lz4hc_mod_init(void)
{
	int ret;

	ret = crypto_register_alg(&alg_lz4hc);
	if (ret)
		return ret;

	ret = crypto_register_scomp(&scomp);
	if (ret) {
		crypto_unregister_alg(&alg_lz4hc);
		return ret;
	}

	return ret;
}

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

subsys_initcall(lz4hc_mod_init);
module_exit(lz4hc_mod_fini);

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