[PATCH 6/6] crypto: cfb - avoid VLA use

[Salvatore Mesoraca]

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=qpxydaacu1rq...@mail.gmail.com

Signed-off-by: Salvatore Mesoraca 
---
 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 
 #include 
 #include 
+#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

[PATCH 6/6] crypto: cfb - avoid VLA use

[Salvatore Mesoraca]

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=qpxydaacu1rq...@mail.gmail.com

Signed-off-by: Salvatore Mesoraca 
---
 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 
 #include 
 #include 
+#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