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From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Jann Horn <jannh@google.com>
Cc: Greg KH <gregkh@linuxfoundation.org>,
	Kees Cook <keescook@chromium.org>,
	kernel list <linux-kernel@vger.kernel.org>,
	Laura Abbott <labbott@redhat.com>,
	Alexander Popov <alex.popov@linux.com>,
	xen-devel <xen-devel@lists.xenproject.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	intel-gfx@lists.freedesktop.org,
	intel-wired-lan@lists.osuosl.org,
	Network Development <netdev@vger.kernel.org>,
	linux-usb <linux-usb@vger.kernel.org>,
	linux-fsdevel@vger.kernel.org, Linux-MM <linux-mm@kvack.org>,
	dev@openvswitch.org,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	linux-security-module <linux-security-module@vger.kernel.org>,
	Kernel Hardening <kernel-hardening@lists.openwall.com>
Subject: Re: [PATCH 1/3] treewide: Lift switch variables out of switches
Date: Wed, 23 Jan 2019 13:12:26 +0100	[thread overview]
Message-ID: <CAKv+Gu-ECKNy+nmnbsetkOg28VR1YkFgnRsu+u9mN4DC_poBwg@mail.gmail.com> (raw)
In-Reply-To: <CAG48ez2vfXkr9dozJiGmze8k49VOXfs=K7M8bv0aQsDDpzrEFQ@mail.gmail.com>

On Wed, 23 Jan 2019 at 13:09, Jann Horn <jannh@google.com> wrote:
>
> On Wed, Jan 23, 2019 at 1:04 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> > On Wed, Jan 23, 2019 at 03:03:47AM -0800, Kees Cook wrote:
> > > Variables declared in a switch statement before any case statements
> > > cannot be initialized, so move all instances out of the switches.
> > > After this, future always-initialized stack variables will work
> > > and not throw warnings like this:
> > >
> > > fs/fcntl.c: In function ‘send_sigio_to_task’:
> > > fs/fcntl.c:738:13: warning: statement will never be executed [-Wswitch-unreachable]
> > >    siginfo_t si;
> > >              ^~
> >
> > That's a pain, so this means we can't have any new variables in { }
> > scope except for at the top of a function?
>
> AFAICS this only applies to switch statements (because they jump to a
> case and don't execute stuff at the start of the block), not blocks
> after if/while/... .
>

I guess that means it may apply to other cases where you do a 'goto'
into the middle of a for() loop, for instance (at the first
iteration), which is also a valid pattern.

Is there any way to tag these assignments so the diagnostic disregards them?

  reply	other threads:[~2019-01-23 12:12 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-23 11:03 [PATCH 0/3] gcc-plugins: Introduce stackinit plugin Kees Cook
2019-01-23 11:03 ` [PATCH 1/3] treewide: Lift switch variables out of switches Kees Cook
2019-01-23 11:58   ` Greg KH
2019-01-23 12:09     ` Jann Horn
2019-01-23 12:12       ` Ard Biesheuvel [this message]
2019-01-23 13:21       ` William Kucharski
2019-01-23 14:17     ` [Intel-gfx] " Jani Nikula
2019-01-23 14:23       ` Jani Nikula
2019-01-23 14:47       ` Edwin Zimmerman
2019-01-23 15:46         ` Jani Nikula
2019-01-23 18:55           ` Kees Cook
2019-01-24  8:10             ` Greg KH
2019-01-23 19:18       ` Matthew Wilcox
2019-01-23 20:36         ` Kees Cook
2019-01-23 16:51   ` [Intel-wired-lan] " Jeff Kirsher
2019-01-24 12:58   ` Edwin Zimmerman
2019-01-23 11:03 ` [PATCH 2/3] gcc-plugins: Introduce stackinit plugin Kees Cook
2019-01-23 11:03 ` [PATCH 3/3] lib: Introduce test_stackinit module Kees Cook
2019-01-29  0:12 ` [PATCH 0/3] gcc-plugins: Introduce stackinit plugin Alexander Popov
2019-02-12 17:54   ` Kees Cook

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