netdev - Re: [PATCH 000/141] Fix fall-through warnings for Clang

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 1 Dec 2020 17:08:49 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Kees Cook <keescook@...omium.org>, alsa-devel@...a-project.org,
        linux-atm-general@...ts.sourceforge.net,
        reiserfs-devel@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-wireless <linux-wireless@...r.kernel.org>,
        linux-fbdev@...r.kernel.org,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Nathan Chancellor <natechancellor@...il.com>,
        linux-ide@...r.kernel.org, dm-devel@...hat.com,
        keyrings@...r.kernel.org, linux-mtd@...ts.infradead.org,
        GR-everest-linux-l2@...vell.com, wcn36xx@...ts.infradead.org,
        samba-technical@...ts.samba.org, linux-i3c@...ts.infradead.org,
        linux1394-devel@...ts.sourceforge.net,
        linux-afs@...ts.infradead.org,
        usb-storage@...ts.one-eyed-alien.net, drbd-dev@...n.linbit.com,
        devel@...verdev.osuosl.org, linux-cifs@...r.kernel.org,
        rds-devel@....oracle.com, linux-scsi@...r.kernel.org,
        linux-rdma@...r.kernel.org, oss-drivers@...ronome.com,
        bridge@...ts.linux-foundation.org,
        linux-security-module@...r.kernel.org,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        linux-stm32@...md-mailman.stormreply.com, cluster-devel@...hat.com,
        linux-acpi@...r.kernel.org, coreteam@...filter.org,
        intel-wired-lan@...ts.osuosl.org, linux-input@...r.kernel.org,
        Miguel Ojeda <ojeda@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>, linux-ext4@...r.kernel.org,
        linux-media@...r.kernel.org, linux-watchdog@...r.kernel.org,
        selinux@...r.kernel.org,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        intel-gfx@...ts.freedesktop.org, linux-geode@...ts.infradead.org,
        linux-can@...r.kernel.org, linux-block@...r.kernel.org,
        linux-gpio@...r.kernel.org, op-tee@...ts.trustedfirmware.org,
        linux-mediatek@...ts.infradead.org, xen-devel@...ts.xenproject.org,
        nouveau@...ts.freedesktop.org, linux-hams@...r.kernel.org,
        ceph-devel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-hwmon@...r.kernel.org,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        linux-nfs@...r.kernel.org, GR-Linux-NIC-Dev@...vell.com,
        tipc-discussion@...ts.sourceforge.net,
        Linux Memory Management List <linux-mm@...ck.org>,
        Network Development <netdev@...r.kernel.org>,
        linux-decnet-user@...ts.sourceforge.net, linux-mmc@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        linux-sctp@...r.kernel.org, linux-usb@...r.kernel.org,
        netfilter-devel@...r.kernel.org,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>, patches@...nsource.cirrus.com,
        Joe Perches <joe@...ches.com>, linux-integrity@...r.kernel.org,
        target-devel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH 000/141] Fix fall-through warnings for Clang

On Mon, Nov 23, 2020 at 05:32:51PM -0800, Nick Desaulniers wrote:
> On Sun, Nov 22, 2020 at 8:17 AM Kees Cook <keescook@...omium.org> wrote:
> >
> > On Fri, Nov 20, 2020 at 11:51:42AM -0800, Jakub Kicinski wrote:
> > > If none of the 140 patches here fix a real bug, and there is no change
> > > to machine code then it sounds to me like a W=2 kind of a warning.
> >
> > FWIW, this series has found at least one bug so far:
> > https://lore.kernel.org/lkml/CAFCwf11izHF=g1mGry1fE5kvFFFrxzhPSM6qKAO8gxSp=Kr_CQ@mail.gmail.com/
> 
> So looks like the bulk of these are:
> switch (x) {
>   case 0:
>     ++x;
>   default:
>     break;
> }

This should not generate a warning.

> 
> I have a patch that fixes those up for clang:
> https://reviews.llvm.org/D91895
> 
> There's 3 other cases that don't quite match between GCC and Clang I
> observe in the kernel:
> switch (x) {
>   case 0:
>     ++x;
>   default:
>     goto y;
> }
> y:;

This should generate a warning.

> 
> switch (x) {
>   case 0:
>     ++x;
>   default:
>     return;
> }

Warn for this.


> 
> switch (x) {
>   case 0:
>     ++x;
>   default:
>     ;
> }

Don't warn for this.

If adding a break statement changes the flow of the code then warn about
potentially missing break statements, but if it doesn't change anything
then don't warn about it.

regards,
dan carpenter