From: Kees Cook <keescook@chromium.org>
Subject: [PATCH 07/11] crypto: xcbc: Remove VLA usage
Date: Wed, 20 Jun 2018 12:04:04 -0700
Message-ID: <20180620190408.45104-8-keescook@chromium.org>
References: <20180620190408.45104-1-keescook@chromium.org>
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Cc: Giovanni Cabiddu <giovanni.cabiddu@intel.com>,
	Kees Cook <keescook@chromium.org>, Arnd Bergmann <arnd@arndb.de>,
	Eric Biggers <ebiggers@google.com>, Mike Snitzer <snitzer@redhat.com>,
	"Gustavo A. R. Silva" <gustavo@embeddedor.com>,
	qat-linux@intel.com, linux-kernel@vger.kernel.org,
	dm-devel@redhat.com, linux-crypto@vger.kernel.org,
	Lars Persson <larper@axis.com>, Tim Chen <tim.c.chen@linux.intel.com>,
	"David S. Miller" <davem@davemloft.net>, Alasdair Kergon <agk@redhat.com>,
	Rabin Vincent <rabinv@axis.com>
To: Herbert Xu <herbert@gondor.apana.org.au>
In-Reply-To: <20180620190408.45104-1-keescook@chromium.org>
Sender: dm-devel-bounces@redhat.com
Errors-To: dm-devel-bounces@redhat.com

In the quest to remove all stack VLA usage from the kernel[1], this uses
the maximum blocksize and adds a sanity check.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 crypto/xcbc.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/crypto/xcbc.c b/crypto/xcbc.c
index 25c75af50d3f..016481b1f3ba 100644
--- a/crypto/xcbc.c
+++ b/crypto/xcbc.c
@@ -65,7 +65,10 @@ static int crypto_xcbc_digest_setkey(struct crypto_shash *parent,
 	int bs = crypto_shash_blocksize(parent);
 	u8 *consts = PTR_ALIGN(&ctx->ctx[0], alignmask + 1);
 	int err = 0;
-	u8 key1[bs];
+	u8 key1[CRYPTO_ALG_MAX_BLOCKSIZE];
+
+	if (WARN_ON(bs > sizeof(key1)))
+		return -EINVAL;
 
 	if ((err = crypto_cipher_setkey(ctx->child, inkey, keylen)))
 		return err;
-- 
2.17.1