Re: [PATCH] infiniband: avoid overflow warning

[Arnd Bergmann]

On Mon, Jul 31, 2017 at 10:58 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> On Mon, Jul 31, 2017 at 12:30 AM, Arnd Bergmann <arnd@xxxxxxxx> wrote:
>> On Mon, Jul 31, 2017 at 9:08 AM, Moni Shoua <monis@xxxxxxxxxxxx> wrote:
>>>>                 break;
>>>>         default:
>>>>                 return -EINVAL;
>>> what happens if you replace 16 with sizeof(struct in6_addr)?
>>
>> Same thing: the problem is that gcc already knows the size of the structure we
>> pass in here, and it is in fact shorter.
>
> So gcc is ignoring both the cast (to 16 byte struct in6_addr) and the
> caller's actual 128 byte struct sockaddr_storage, and looking only at
> struct sockaddr? That seems really weird.

Using a sockaddr_storage on the stack would address the warning, but
the question was about just changing the hardcoded 16 to a sizeof()
operation, and that has no effect.

        Arnd