[PATCH v5 02/11] crypto: cbc: Remove VLA usage

From: Kees Cook <keescook@chromium.org>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Kees Cook <keescook@chromium.org>, Arnd Bergmann <arnd@arndb.de>,
	Eric Biggers <ebiggers@google.com>,
	"Gustavo A. R. Silva" <gustavo@embeddedor.com>,
	Alasdair Kergon <agk@redhat.com>,
	Giovanni Cabiddu <giovanni.cabiddu@intel.com>,
	Lars Persson <larper@axis.com>, Mike Snitzer <snitzer@redhat.com>,
	Rabin Vincent <rabinv@axis.com>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	linux-crypto@vger.kernel.org, qat-linux@intel.com,
	dm-devel@redhat.com, linux-kernel@vger.kernel.org
Subject: [PATCH v5 02/11] crypto: cbc: Remove VLA usage
Date: Mon, 16 Jul 2018 21:21:41 -0700	[thread overview]
Message-ID: <20180717042150.37761-3-keescook@chromium.org> (raw)
In-Reply-To: <20180717042150.37761-1-keescook@chromium.org>

In the quest to remove all stack VLA usage from the kernel[1], this
uses the upper bounds on blocksize. Since this is always a cipher
blocksize, use the existing cipher max blocksize.

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

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/crypto/cbc.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/crypto/cbc.h b/include/crypto/cbc.h
index f5b8bfc22e6d..47db0aac2ab9 100644
--- a/include/crypto/cbc.h
+++ b/include/crypto/cbc.h
@@ -113,7 +113,9 @@ static inline int crypto_cbc_decrypt_inplace(
 	unsigned int bsize = crypto_skcipher_blocksize(tfm);
 	unsigned int nbytes = walk->nbytes;
 	u8 *src = walk->src.virt.addr;
-	u8 last_iv[bsize];
+	u8 last_iv[MAX_CIPHER_BLOCKSIZE];
+
+	BUG_ON(bsize > sizeof(last_iv));
 
 	/* Start of the last block. */
 	src += nbytes - (nbytes & (bsize - 1)) - bsize;
-- 
2.17.1
