Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751496AbdGaVKJ (ORCPT ); Mon, 31 Jul 2017 17:10:09 -0400 Received: from mail-oi0-f65.google.com ([209.85.218.65]:35913 "EHLO mail-oi0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751052AbdGaVKI (ORCPT ); Mon, 31 Jul 2017 17:10:08 -0400 MIME-Version: 1.0 In-Reply-To: References: <20170731065016.2947796-1-arnd@arndb.de> From: Arnd Bergmann Date: Mon, 31 Jul 2017 23:10:07 +0200 X-Google-Sender-Auth: zsJe2eHyd244pCpyKLIIXKULOXI Message-ID: Subject: Re: [PATCH] infiniband: avoid overflow warning To: Kees Cook Cc: Moni Shoua , Doug Ledford , Sean Hefty , Hal Rosenstock , Daniel Micay , "Kalderon, Michal" , Ariel Elior , "David S. Miller" , Bart Van Assche , Parav Pandit , Noa Osherovich , linux-rdma , Linux Kernel Mailinglist Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 881 Lines: 20 On Mon, Jul 31, 2017 at 10:58 PM, Kees Cook wrote: > On Mon, Jul 31, 2017 at 12:30 AM, Arnd Bergmann wrote: >> On Mon, Jul 31, 2017 at 9:08 AM, Moni Shoua 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