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]
Message-ID: <202011201129.B13FDB3C@keescook>
Date:   Fri, 20 Nov 2020 11:30:40 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-kernel@...r.kernel.org, alsa-devel@...a-project.org,
        amd-gfx@...ts.freedesktop.org, bridge@...ts.linux-foundation.org,
        ceph-devel@...r.kernel.org, cluster-devel@...hat.com,
        coreteam@...filter.org, devel@...verdev.osuosl.org,
        dm-devel@...hat.com, drbd-dev@...ts.linbit.com,
        dri-devel@...ts.freedesktop.org, GR-everest-linux-l2@...vell.com,
        GR-Linux-NIC-Dev@...vell.com, intel-gfx@...ts.freedesktop.org,
        intel-wired-lan@...ts.osuosl.org, keyrings@...r.kernel.org,
        linux1394-devel@...ts.sourceforge.net, linux-acpi@...r.kernel.org,
        linux-afs@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org,
        linux-atm-general@...ts.sourceforge.net,
        linux-block@...r.kernel.org, linux-can@...r.kernel.org,
        linux-cifs@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-decnet-user@...ts.sourceforge.net,
        linux-ext4@...r.kernel.org, linux-fbdev@...r.kernel.org,
        linux-geode@...ts.infradead.org, linux-gpio@...r.kernel.org,
        linux-hams@...r.kernel.org, linux-hwmon@...r.kernel.org,
        linux-i3c@...ts.infradead.org, linux-ide@...r.kernel.org,
        linux-iio@...r.kernel.org, linux-input@...r.kernel.org,
        linux-integrity@...r.kernel.org,
        linux-mediatek@...ts.infradead.org, linux-media@...r.kernel.org,
        linux-mmc@...r.kernel.org, linux-mm@...ck.org,
        linux-mtd@...ts.infradead.org, linux-nfs@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-sctp@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-usb@...r.kernel.org, linux-watchdog@...r.kernel.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        netfilter-devel@...r.kernel.org, nouveau@...ts.freedesktop.org,
        op-tee@...ts.trustedfirmware.org, oss-drivers@...ronome.com,
        patches@...nsource.cirrus.com, rds-devel@....oracle.com,
        reiserfs-devel@...r.kernel.org, samba-technical@...ts.samba.org,
        selinux@...r.kernel.org, target-devel@...r.kernel.org,
        tipc-discussion@...ts.sourceforge.net,
        usb-storage@...ts.one-eyed-alien.net,
        virtualization@...ts.linux-foundation.org,
        wcn36xx@...ts.infradead.org, x86@...nel.org,
        xen-devel@...ts.xenproject.org, linux-hardening@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Miguel Ojeda <ojeda@...nel.org>, Joe Perches <joe@...ches.com>
Subject: Re: [PATCH 000/141] Fix fall-through warnings for Clang

On Fri, Nov 20, 2020 at 10:53:44AM -0800, Jakub Kicinski wrote:
> On Fri, 20 Nov 2020 12:21:39 -0600 Gustavo A. R. Silva wrote:
> > This series aims to fix almost all remaining fall-through warnings in
> > order to enable -Wimplicit-fallthrough for Clang.
> > 
> > In preparation to enable -Wimplicit-fallthrough for Clang, explicitly
> > add multiple break/goto/return/fallthrough statements instead of just
> > letting the code fall through to the next case.
> > 
> > Notice that in order to enable -Wimplicit-fallthrough for Clang, this
> > change[1] is meant to be reverted at some point. So, this patch helps
> > to move in that direction.
> > 
> > Something important to mention is that there is currently a discrepancy
> > between GCC and Clang when dealing with switch fall-through to empty case
> > statements or to cases that only contain a break/continue/return
> > statement[2][3][4].
> 
> Are we sure we want to make this change? Was it discussed before?
> 
> Are there any bugs Clangs puritanical definition of fallthrough helped
> find?
> 
> IMVHO compiler warnings are supposed to warn about issues that could
> be bugs. Falling through to default: break; can hardly be a bug?!

It's certainly a place where the intent is not always clear. I think
this makes all the cases unambiguous, and doesn't impact the machine
code, since the compiler will happily optimize away any behavioral
redundancy.


-- 
Kees Cook

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ