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> --- 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
