On 04/10/18 05:52 PM, Kees Cook wrote:
> In the quest to remove VLAs from the kernel[1], this replaces the VLA
> size with the only possible size used in the code, and adds a mechanism
> to double-check future IV sizes.
>
> [1]
> https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qpxydaacu1rq...@mail.gmail.com
>
> Signed-off-by: Kees Cook <keesc...@chromium.org>
Thanks
Acked-by: Dave Watson <davejwat...@fb.com>
> ---
> net/tls/tls_sw.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
> index 4dc766b03f00..71e79597f940 100644
> --- a/net/tls/tls_sw.c
> +++ b/net/tls/tls_sw.c
> @@ -41,6 +41,8 @@
> #include <net/strparser.h>
> #include <net/tls.h>
>
> +#define MAX_IV_SIZE TLS_CIPHER_AES_GCM_128_IV_SIZE
> +
> static int tls_do_decryption(struct sock *sk,
> struct scatterlist *sgin,
> struct scatterlist *sgout,
> @@ -673,7 +675,7 @@ static int decrypt_skb(struct sock *sk, struct sk_buff
> *skb,
> {
> struct tls_context *tls_ctx = tls_get_ctx(sk);
> struct tls_sw_context *ctx = tls_sw_ctx(tls_ctx);
> - char iv[TLS_CIPHER_AES_GCM_128_SALT_SIZE + tls_ctx->rx.iv_size];
> + char iv[TLS_CIPHER_AES_GCM_128_SALT_SIZE + MAX_IV_SIZE];
> struct scatterlist sgin_arr[MAX_SKB_FRAGS + 2];
> struct scatterlist *sgin = &sgin_arr[0];
> struct strp_msg *rxm = strp_msg(skb);
> @@ -1094,6 +1096,12 @@ int tls_set_sw_offload(struct sock *sk, struct
> tls_context *ctx, int tx)
> goto free_priv;
> }
>
> + /* Sanity-check the IV size for stack allocations. */
> + if (iv_size > MAX_IV_SIZE) {
> + rc = -EINVAL;
> + goto free_priv;
> + }
> +
> cctx->prepend_size = TLS_HEADER_SIZE + nonce_size;
> cctx->tag_size = tag_size;
> cctx->overhead_size = cctx->prepend_size + cctx->tag_size;
> --
> 2.7.4
>
>
> --
> Kees Cook
> Pixel Security
