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From: Andy Lutomirski <luto@amacapital.net>
Date: Wed, 4 May 2016 16:02:55 -0700
Message-ID: <CALCETrVzhzF_xJeYVNhg4XtQucbvYzbwaNFEpitLzpBPeAtdVA@mail.gmail.com>
Subject: Re: [PATCH 1/4] signals/sigaltstack: If SS_AUTODISARM, bypass on_sig_stack
To: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>, Shuah Khan <shuahkh@osg.samsung.com>,
        Pavel Emelyanov <xemul@parallels.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Jason Low <jason.low2@hp.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Josh Triplett <josh@joshtriplett.org>,
        Aleksa Sarai <cyphar@cyphar.com>, Paul Moore <pmoore@redhat.com>,
        X86 ML <x86@kernel.org>, Sasha Levin <sasha.levin@oracle.com>,
        Stas Sergeev <stsp@list.ru>, Denys Vlasenko <dvlasenk@redhat.com>,
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        Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
        Heinrich Schuchardt <xypron.glpk@gmx.de>, Tejun Heo <tj@kernel.org>,
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On May 3, 2016 11:32 PM, "Ingo Molnar" <mingo@kernel.org> wrote:
>
>
> * Andy Lutomirski <luto@kernel.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@list.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