linux-kernel - [PATCH 07/11] crypto: xcbc: Remove VLA usage

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Date:   Wed, 20 Jun 2018 12:04:04 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Alasdair Kergon <agk@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Eric Biggers <ebiggers@...gle.com>,
        Giovanni Cabiddu <giovanni.cabiddu@...el.com>,
        Lars Persson <larper@...s.com>,
        Mike Snitzer <snitzer@...hat.com>,
        Rabin Vincent <rabinv@...s.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        "David S. Miller" <davem@...emloft.net>,
        linux-crypto@...r.kernel.org, qat-linux@...el.com,
        dm-devel@...hat.com, linux-kernel@...r.kernel.org
Subject: [PATCH 07/11] crypto: xcbc: Remove VLA usage

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@...omium.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