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

Kees Cook
2018-08-02T23:46:05Z

On Tue, Jul 24, 2018 at 9:49 AM, Kees Cook <keescook@chromium.org> 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@chromium.org>
> Acked-by: Arnd Bergmann <arnd@arndb.de>

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