Re: [PATCH v6 16/18] rxrpc: Reuse SKCIPHER_REQUEST_ON_STACK buffer

[Kees Cook]

On Tue, Jul 24, 2018 at 9:49 AM, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> The use of SKCIPHER_REQUEST_ON_STACK() will trigger FRAME_WARN warnings
> (when less than 2048) once the VLA is no longer hidden from the check:
>
> net/rxrpc/rxkad.c:398:1: warning: the frame size of 1152 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> net/rxrpc/rxkad.c:242:1: warning: the frame size of 1152 bytes is larger than 1024 bytes [-Wframe-larger-than=]
>
> This passes the initial SKCIPHER_REQUEST_ON_STACK allocation to the leaf
> functions for reuse. Two requests allocated on the stack is not needed
> when only one is used at a time.
>
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> Acked-by: Arnd Bergmann <arnd@xxxxxxxx>

David (Howells), what do you think of this? Can this go via your tree
or maybe via netdev?

I'd love your Ack or Review. :)

Thanks,

-Kees

> ---
>  net/rxrpc/rxkad.c | 25 +++++++++++++------------
>  1 file changed, 13 insertions(+), 12 deletions(-)
>
> diff --git a/net/rxrpc/rxkad.c b/net/rxrpc/rxkad.c
> index 278ac0807a60..6393391fac86 100644
> --- a/net/rxrpc/rxkad.c
> +++ b/net/rxrpc/rxkad.c
> @@ -146,10 +146,10 @@ static int rxkad_prime_packet_security(struct rxrpc_connection *conn)
>  static int rxkad_secure_packet_auth(const struct rxrpc_call *call,
>                                     struct sk_buff *skb,
>                                     u32 data_size,
> -                                   void *sechdr)
> +                                   void *sechdr,
> +                                   struct skcipher_request *req)
>  {
>         struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
> -       SKCIPHER_REQUEST_ON_STACK(req, call->conn->cipher);
>         struct rxkad_level1_hdr hdr;
>         struct rxrpc_crypt iv;
>         struct scatterlist sg;
> @@ -183,12 +183,12 @@ static int rxkad_secure_packet_auth(const struct rxrpc_call *call,
>  static int rxkad_secure_packet_encrypt(const struct rxrpc_call *call,
>                                        struct sk_buff *skb,
>                                        u32 data_size,
> -                                      void *sechdr)
> +                                      void *sechdr,
> +                                      struct skcipher_request *req)
>  {
>         const struct rxrpc_key_token *token;
>         struct rxkad_level2_hdr rxkhdr;
>         struct rxrpc_skb_priv *sp;
> -       SKCIPHER_REQUEST_ON_STACK(req, call->conn->cipher);
>         struct rxrpc_crypt iv;
>         struct scatterlist sg[16];
>         struct sk_buff *trailer;
> @@ -296,11 +296,12 @@ static int rxkad_secure_packet(struct rxrpc_call *call,
>                 ret = 0;
>                 break;
>         case RXRPC_SECURITY_AUTH:
> -               ret = rxkad_secure_packet_auth(call, skb, data_size, sechdr);
> +               ret = rxkad_secure_packet_auth(call, skb, data_size, sechdr,
> +                                              req);
>                 break;
>         case RXRPC_SECURITY_ENCRYPT:
>                 ret = rxkad_secure_packet_encrypt(call, skb, data_size,
> -                                                 sechdr);
> +                                                 sechdr, req);
>                 break;
>         default:
>                 ret = -EPERM;
> @@ -316,10 +317,10 @@ static int rxkad_secure_packet(struct rxrpc_call *call,
>   */
>  static int rxkad_verify_packet_1(struct rxrpc_call *call, struct sk_buff *skb,
>                                  unsigned int offset, unsigned int len,
> -                                rxrpc_seq_t seq)
> +                                rxrpc_seq_t seq,
> +                                struct skcipher_request *req)
>  {
>         struct rxkad_level1_hdr sechdr;
> -       SKCIPHER_REQUEST_ON_STACK(req, call->conn->cipher);
>         struct rxrpc_crypt iv;
>         struct scatterlist sg[16];
>         struct sk_buff *trailer;
> @@ -402,11 +403,11 @@ static int rxkad_verify_packet_1(struct rxrpc_call *call, struct sk_buff *skb,
>   */
>  static int rxkad_verify_packet_2(struct rxrpc_call *call, struct sk_buff *skb,
>                                  unsigned int offset, unsigned int len,
> -                                rxrpc_seq_t seq)
> +                                rxrpc_seq_t seq,
> +                                struct skcipher_request *req)
>  {
>         const struct rxrpc_key_token *token;
>         struct rxkad_level2_hdr sechdr;
> -       SKCIPHER_REQUEST_ON_STACK(req, call->conn->cipher);
>         struct rxrpc_crypt iv;
>         struct scatterlist _sg[4], *sg;
>         struct sk_buff *trailer;
> @@ -549,9 +550,9 @@ static int rxkad_verify_packet(struct rxrpc_call *call, struct sk_buff *skb,
>         case RXRPC_SECURITY_PLAIN:
>                 return 0;
>         case RXRPC_SECURITY_AUTH:
> -               return rxkad_verify_packet_1(call, skb, offset, len, seq);
> +               return rxkad_verify_packet_1(call, skb, offset, len, seq, req);
>         case RXRPC_SECURITY_ENCRYPT:
> -               return rxkad_verify_packet_2(call, skb, offset, len, seq);
> +               return rxkad_verify_packet_2(call, skb, offset, len, seq, req);
>         default:
>                 return -ENOANO;
>         }
> --
> 2.17.1
>



-- 
Kees Cook
Pixel Security