Re: [PATCH] infiniband: avoid overflow warning

Arnd Bergmann
2017-07-31T21:10:07Z

On Mon, Jul 31, 2017 at 10:58 PM, Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org> wrote:
> On Mon, Jul 31, 2017 at 12:30 AM, Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org> wrote:
>> On Mon, Jul 31, 2017 at 9:08 AM, Moni Shoua <monis-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org> 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