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Message-Id: <1523282044-22075-7-git-send-email-s.mesoraca16@gmail.com>
Date: Mon, 9 Apr 2018 15:54:04 +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 6/6] crypto: cfb - avoid VLA use
We avoid 3 VLAs[1] by always allocating MAX_BLOCKSIZE bytes or,
when needed for alignement, 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/cfb.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/crypto/cfb.c b/crypto/cfb.c
index 94ee39b..f500816 100644
--- a/crypto/cfb.c
+++ b/crypto/cfb.c
@@ -28,6 +28,7 @@
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/types.h>
+#include "internal.h"
struct crypto_cfb_ctx {
struct crypto_cipher *child;
@@ -53,9 +54,8 @@ static void crypto_cfb_encrypt_one(struct crypto_skcipher *tfm,
static void crypto_cfb_final(struct skcipher_walk *walk,
struct crypto_skcipher *tfm)
{
- const unsigned int bsize = crypto_cfb_bsize(tfm);
const unsigned long alignmask = crypto_skcipher_alignmask(tfm);
- u8 tmp[bsize + alignmask];
+ u8 tmp[MAX_BLOCKSIZE + MAX_ALIGNMASK];
u8 *stream = PTR_ALIGN(tmp + 0, alignmask + 1);
u8 *src = walk->src.virt.addr;
u8 *dst = walk->dst.virt.addr;
@@ -94,7 +94,7 @@ static int crypto_cfb_encrypt_inplace(struct skcipher_walk *walk,
unsigned int nbytes = walk->nbytes;
u8 *src = walk->src.virt.addr;
u8 *iv = walk->iv;
- u8 tmp[bsize];
+ u8 tmp[MAX_BLOCKSIZE];
do {
crypto_cfb_encrypt_one(tfm, iv, tmp);
@@ -164,7 +164,7 @@ static int crypto_cfb_decrypt_inplace(struct skcipher_walk *walk,
unsigned int nbytes = walk->nbytes;
u8 *src = walk->src.virt.addr;
u8 *iv = walk->iv;
- u8 tmp[bsize];
+ u8 tmp[MAX_BLOCKSIZE];
do {
crypto_cfb_encrypt_one(tfm, iv, tmp);
@@ -295,6 +295,12 @@ static int crypto_cfb_create(struct crypto_template *tmpl, struct rtattr **tb)
if (err)
goto err_drop_spawn;
+ err = -EINVAL;
+ if (alg->cra_blocksize > MAX_BLOCKSIZE)
+ goto err_drop_spawn;
+ if (alg->cra_alignmask > MAX_ALIGNMASK)
+ goto err_drop_spawn;
+
inst->alg.base.cra_priority = alg->cra_priority;
/* we're a stream cipher independend of the crypto cra_blocksize */
inst->alg.base.cra_blocksize = 1;
--
1.9.1
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