Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754018AbdGXLfU (ORCPT ); Mon, 24 Jul 2017 07:35:20 -0400 Received: from mail-ua0-f172.google.com ([209.85.217.172]:36161 "EHLO mail-ua0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752772AbdGXLfO (ORCPT ); Mon, 24 Jul 2017 07:35:14 -0400 MIME-Version: 1.0 In-Reply-To: <20170721210251.3378996-1-arnd@arndb.de> References: <20170721210251.3378996-1-arnd@arndb.de> From: Alexander Potapenko Date: Mon, 24 Jul 2017 13:35:11 +0200 Message-ID: Subject: Re: [PATCH] [v2] kasan: avoid -Wmaybe-uninitialized warning To: Arnd Bergmann Cc: Andrey Ryabinin , Dmitry Vyukov , Andrew Morton , Andrey Konovalov , kasan-dev , Linux Memory Management List , LKML 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-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id v6OBZRKF032382 Content-Length: 2125 Lines: 60 On Fri, Jul 21, 2017 at 11:02 PM, Arnd Bergmann wrote: > gcc-7 produces this warning: > > mm/kasan/report.c: In function 'kasan_report': > mm/kasan/report.c:351:3: error: 'info.first_bad_addr' may be used uninitialized in this function [-Werror=maybe-uninitialized] > print_shadow_for_address(info->first_bad_addr); > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > mm/kasan/report.c:360:27: note: 'info.first_bad_addr' was declared here > > The code seems fine as we only print info.first_bad_addr when there is a shadow, > and we always initialize it in that case, but this is relatively hard > for gcc to figure out after the latest rework. Adding an intialization > in the other code path gets rid of the warning. > > Fixes: b235b9808664 ("kasan: unify report headers") > Link: https://patchwork.kernel.org/patch/9641417/ > Acked-by: Dmitry Vyukov > Signed-off-by: Arnd Bergmann > --- > Originally submitted on March 23, but unfortunately is still needed, > as verified on 4.13-rc1, with aarch64-linux-gcc-7.1.1 > > v2: add a comment as Andrew suggested > --- > mm/kasan/report.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/kasan/report.c b/mm/kasan/report.c > index 04bb1d3eb9ec..28fb222ab149 100644 > --- a/mm/kasan/report.c > +++ b/mm/kasan/report.c > @@ -111,6 +111,9 @@ static const char *get_wild_bug_type(struct kasan_access_info *info) > { > const char *bug_type = "unknown-crash"; > > + /* shut up spurious -Wmaybe-uninitialized warning */ > + info->first_bad_addr = (void *)(-1ul); > + Why don't we initialize info.first_bad_addr in kasan_report(), where info is allocated? > if ((unsigned long)info->access_addr < PAGE_SIZE) > bug_type = "null-ptr-deref"; > else if ((unsigned long)info->access_addr < TASK_SIZE) > -- > 2.9.0 > -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Matthew Scott Sucherman, Paul Terence Manicle Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg