Re: crypto: s390/aes - Fix buffer overread in CTR mode

Harald Freudenberger
2023-11-28T13:18:07Z

On 2023-11-28 07:22, Herbert Xu wrote:
> When processing the last block, the s390 ctr code will always read
> a whole block, even if there isn't a whole block of data left. Fix
> this by using the actual length left and copy it into a buffer first
> for processing.
>
> Fixes: 0200f3ecc196 ("crypto: s390 - add System z hardware support for
> CTR mode")
> Cc: <stable@vger.kernel.org>
> Reported-by: Guangwu Zhang <guazhang@redhat.com>
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
>
> diff --git a/arch/s390/crypto/aes_s390.c b/arch/s390/crypto/aes_s390.c
> index c773820e4af9..c6fe5405de4a 100644
> --- a/arch/s390/crypto/aes_s390.c
> +++ b/arch/s390/crypto/aes_s390.c
> @@ -597,7 +597,9 @@ static int ctr_aes_crypt(struct skcipher_request
> *req)
> * final block may be < AES_BLOCK_SIZE, copy only nbytes
> */
> if (nbytes) {
> - cpacf_kmctr(sctx->fc, sctx->key, buf, walk.src.virt.addr,
> + memset(buf, 0, AES_BLOCK_SIZE);
> + memcpy(buf, walk.src.virt.addr, nbytes);
> + cpacf_kmctr(sctx->fc, sctx->key, buf, buf,
> AES_BLOCK_SIZE, walk.iv);
> memcpy(walk.dst.virt.addr, buf, nbytes);
> crypto_inc(walk.iv, AES_BLOCK_SIZE);

Here is a similar fix for the s390 paes ctr cipher. Compiles and is
tested. You may merge this with your patch for the s390 aes cipher.

--------------------------------------------------------------------------------

diff --git a/arch/s390/crypto/paes_s390.c b/arch/s390/crypto/paes_s390.c
index 8b541e44151d..55ee5567a5ea 100644
--- a/arch/s390/crypto/paes_s390.c
+++ b/arch/s390/crypto/paes_s390.c
@@ -693,9 +693,11 @@ static int ctr_paes_crypt(struct skcipher_request
*req)
* final block may be < AES_BLOCK_SIZE, copy only nbytes
*/
if (nbytes) {
+ memset(buf, 0, AES_BLOCK_SIZE);
+ memcpy(buf, walk.src.virt.addr, nbytes);
while (1) {
if (cpacf_kmctr(ctx->fc, &param, buf,
- walk.src.virt.addr,
AES_BLOCK_SIZE,
+ buf, AES_BLOCK_SIZE,
walk.iv) == AES_BLOCK_SIZE)
break;
if (__paes_convert_key(ctx))