linux-kernel - Re: [PATCH 1/4] signals/sigaltstack: If SS_AUTODISARM, bypass on_sig

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Message-ID: <CALCETrVzhzF_xJeYVNhg4XtQucbvYzbwaNFEpitLzpBPeAtdVA@mail.gmail.com>
Date:	Wed, 4 May 2016 16:02:55 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Shuah Khan <shuahkh@....samsung.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jason Low <jason.low2@...com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Josh Triplett <josh@...htriplett.org>,
	Aleksa Sarai <cyphar@...har.com>,
	Paul Moore <pmoore@...hat.com>, X86 ML <x86@...nel.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	Stas Sergeev <stsp@...t.ru>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	"Amanieu d'Antras" <amanieu@...il.com>,
	Borislav Petkov <bp@...en8.de>,
	Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
	Heinrich Schuchardt <xypron.glpk@....de>,
	Tejun Heo <tj@...nel.org>, Brian Gerst <brgerst@...il.com>,
	Linux API <linux-api@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Palmer Dabbelt <palmer@...belt.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Vladimir Davydov <vdavydov@...allels.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Richard Weinberger <richard@....at>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 1/4] signals/sigaltstack: If SS_AUTODISARM, bypass on_sig_stack

On May 3, 2016 11:32 PM, "Ingo Molnar" <mingo@...nel.org> wrote:
>
>
> * Andy Lutomirski <luto@...nel.org> wrote:
>
> > If a signal stack is set up with SS_AUTODISARM, then the kernel
> > inherently avoids incorrectly resetting the signal stack if signals
> > recurse: the signal stack will be reset on the first signal
> > delivery.  This means that we don't need check the stack pointer
> > when delivering signals if SS_AUTODISARM is set.
> >
> > This will make segmented x86 programs more robust: currently there's
> > a hole that could be triggered if ESP/RSP appears to point to the
> > signal stack but actually doesn't due to a nonzero SS base.
> >
> > Signed-off-by: Stas Sergeev <stsp@...t.ru>
>
> Presuably that SOB from Stas is stray, as there's no matching From: line?
> I've removed it.

Yes.  It was a cut-and-paste-o -- I meant to change it to cc.

>
> Thanks,
>
>         Ingo