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Message-Id: <1523126303-23205-3-git-send-email-s.mesoraca16@gmail.com>
Date: Sat, 7 Apr 2018 20:38:19 +0200
From: Salvatore Mesoraca <s.mesoraca16@...il.com>
To: linux-kernel@...r.kernel.org
Cc: kernel-hardening@...ts.openwall.com,
linux-crypto@...r.kernel.org,
"David S. Miller" <davem@...emloft.net>,
Herbert Xu <herbert@...dor.apana.org.au>,
Kees Cook <keescook@...omium.org>,
Salvatore Mesoraca <s.mesoraca16@...il.com>,
Eric Biggers <ebiggers3@...il.com>,
Laura Abbott <labbott@...hat.com>
Subject: [PATCH 2/6] crypto: ctr - avoid VLA use
We avoid 2 VLAs[1] by always allocating MAX_BLOCKSIZE +
MAX_ALIGNMASK bytes.
We also check the selected cipher at instance creation time, if
it doesn't comply with these limits, the creation will fail.
[1] http://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
Signed-off-by: Salvatore Mesoraca <s.mesoraca16@...il.com>
---
crypto/ctr.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/crypto/ctr.c b/crypto/ctr.c
index 854d924..ce62552 100644
--- a/crypto/ctr.c
+++ b/crypto/ctr.c
@@ -20,6 +20,7 @@
#include <linux/random.h>
#include <linux/scatterlist.h>
#include <linux/slab.h>
+#include "internal.h"
struct crypto_ctr_ctx {
struct crypto_cipher *child;
@@ -58,7 +59,7 @@ static void crypto_ctr_crypt_final(struct blkcipher_walk *walk,
unsigned int bsize = crypto_cipher_blocksize(tfm);
unsigned long alignmask = crypto_cipher_alignmask(tfm);
u8 *ctrblk = walk->iv;
- u8 tmp[bsize + alignmask];
+ u8 tmp[MAX_BLOCKSIZE + MAX_ALIGNMASK];
u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
u8 *src = walk->src.virt.addr;
u8 *dst = walk->dst.virt.addr;
@@ -106,7 +107,7 @@ static int crypto_ctr_crypt_inplace(struct blkcipher_walk *walk,
unsigned int nbytes = walk->nbytes;
u8 *ctrblk = walk->iv;
u8 *src = walk->src.virt.addr;
- u8 tmp[bsize + alignmask];
+ u8 tmp[MAX_BLOCKSIZE + MAX_ALIGNMASK];
u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
do {
@@ -206,6 +207,14 @@ static struct crypto_instance *crypto_ctr_alloc(struct rtattr **tb)
if (alg->cra_blocksize < 4)
goto out_put_alg;
+ /* Block size must be <= MAX_BLOCKSIZE. */
+ if (alg->cra_blocksize > MAX_BLOCKSIZE)
+ goto out_put_alg;
+
+ /* Alignmask must be <= MAX_ALIGNMASK. */
+ if (alg->cra_alignmask > MAX_ALIGNMASK)
+ goto out_put_alg;
+
/* If this is false we'd fail the alignment of crypto_inc. */
if (alg->cra_blocksize % 4)
goto out_put_alg;
--
1.9.1
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