Re: [PATCH] infiniband: avoid overflow warning

[Moni Shoua]

On Mon, Jul 31, 2017 at 9:50 AM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> A sockaddr_in structure on the stack getting passed into rdma_ip2gid
> triggers this warning, since we memcpy into a larger sockaddr_in6
> structure:
>
> In function 'memcpy',
>     inlined from 'rdma_ip2gid' at include/rdma/ib_addr.h:175:3,
>     inlined from 'addr_event.isra.4.constprop' at drivers/infiniband/core/roce_gid_mgmt.c:693:2,
>     inlined from 'inetaddr_event' at drivers/infiniband/core/roce_gid_mgmt.c:716:9:
> include/linux/string.h:305:4: error: call to '__read_overflow2' declared with attribute error: detected read beyond size of object passed as 2nd parameter
>
> The warning seems appropriate here, but the code is also clearly
> correct, so we really just want to shut up this instance of the
> output.
>
> The best way I found so far is to avoid the memcpy() call and instead
> replace it with a struct assignment.
>
> Fixes: 6974f0c4555e ("include/linux/string.h: add the option of fortified string.h functions")
> Cc: Daniel Micay <danielmicay@xxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
>  include/rdma/ib_addr.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/rdma/ib_addr.h b/include/rdma/ib_addr.h
> index 7aca12188ef3..ec5008cf5d51 100644
> --- a/include/rdma/ib_addr.h
> +++ b/include/rdma/ib_addr.h
> @@ -172,7 +172,8 @@ static inline int rdma_ip2gid(struct sockaddr *addr, union ib_gid *gid)
>                                        (struct in6_addr *)gid);
>                 break;
>         case AF_INET6:
> -               memcpy(gid->raw, &((struct sockaddr_in6 *)addr)->sin6_addr, 16);
> +               *(struct in6_addr *)&gid->raw =
> +                       ((struct sockaddr_in6 *)addr)->sin6_addr;
>                 break;
>         default:
>                 return -EINVAL;
what happens if you replace 16 with sizeof(struct in6_addr)?