Re: [PATCH] rxrpc: Reuse SKCIPHER_REQUEST_ON_STACK buffer

[Arnd Bergmann]

On Mon, Jul 16, 2018 at 5:49 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 are not needed
> when only one is used at a time.
>
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>

This looks like a very nice solution to the problem.

Acked-by: Arnd Bergmann <arnd@xxxxxxxx>

Since the large stack usage could already cause problems in older kernels,
should this be backported to stable kernels as well?

      Arnd