linux-kernel - Re: [PATCH 0/2] Don't use SIGMINSTKSZ when enforcing alternative signal stack size for compat tasks

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Date:   Tue, 30 Jul 2019 10:27:31 +0100
From:   Will Deacon <will@...nel.org>
To:     Will Deacon <will.deacon@....com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, arnd@...db.de,
        linux@...inikbrodowski.net, ebiederm@...ssion.com,
        akpm@...ux-foundation.org, viro@...iv.linux.org.uk,
        oleg@...hat.com, steve.mcintyre@....com, dave.martin@....com
Subject: Re: [PATCH 0/2] Don't use SIGMINSTKSZ when enforcing alternative
 signal stack size for compat tasks

On Mon, Jul 29, 2019 at 10:23:02PM +0200, Aurelien Jarno wrote:
> On 2018-07-25 14:45, Will Deacon wrote:
> > Hi all,
> > 
> > The Debian folks have observed a failure in the 32-bit arm glibc testsuite
> > when running under a 64-bit kernel. They tracked this down to sigaltstack(2)
> > enforcing the alternative signal stack to be at least SIGMINSTKSZ bytes,
> > which is higher for native arm64 tasks than compat 32-bit tasks.
> > 
> > These patches resolve the issue by allowing an architecture to define
> > COMPAT_SIGMINSTKSZ for compat tasks, which is then used by the sigaltstack
> > checking code.
> > 
> > Feedback welcome,
> > 
> > Will
> > 
> > --->8
> > 
> > Will Deacon (2):
> >   signal: Introduce COMPAT_SIGMINSTKSZ for use in compat_sys_sigaltstack
> >   arm64: compat: Provide definition for COMPAT_SIGMINSTKSZ
> 
> Only the first patch went to the stable kernels. The second one is
> missing, so the bug is still not fixed in those kernels. Would it be
> possible to also get it included?

Damn, you're right. I think the autosel bot picked the first commit but not
the second. In hindsight, we should've tagged them both, but oh well. I've
posted the patch here for -stable, with you on cc:

https://lore.kernel.org/lkml/20190730092547.1284-1-will@kernel.org/T/#u

Will