linux-kernel - Re: [PATCH] x86/crypto: Add missing RETs

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Message-ID: <20180626064930.GB25879@gmail.com>
Date:   Tue, 26 Jun 2018 08:49:30 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Alexey Dobriyan <adobriyan@...il.com>,
        Borislav Petkov <bp@...en8.de>, linux-crypto@...r.kernel.org,
        Mike Galbraith <efault@....de>, torvalds@...ux-foundation.org,
        tglx@...utronix.de, luto@...nel.org, peterz@...radead.org,
        brgerst@...il.com, hpa@...or.com, linux-kernel@...r.kernel.org,
        dvlasenk@...hat.com, h.peter.anvin@...el.com,
        linux-tip-commits <linux-tip-commits@...r.kernel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] x86/crypto: Add missing RETs


* Josh Poimboeuf <jpoimboe@...hat.com> wrote:

> On Mon, Jun 25, 2018 at 09:24:38AM +0200, Ingo Molnar wrote:
> > 
> > * Alexey Dobriyan <adobriyan@...il.com> wrote:
> > 
> > > On Sun, Jun 24, 2018 at 09:11:05AM +0200, Ingo Molnar wrote:
> > > > > Add explicit RETs to the tail calls of AEGIS and MORUS crypto algorithms
> > > > > otherwise they run into INT3 padding due to
> > > > > 
> > > > >   51bad67ffbce ("x86/asm: Pad assembly functions with INT3 instructions")
> > > > > 
> > > > > leading to spurious debug exceptions.
> > > > > 
> > > > > Mike Galbraith <efault@....de> took care of all the remaining callsites.
> > > > 
> > > > Note that 51bad67ffbce has been zapped because it caused too many problems like 
> > > > this, but the explicit RETs make sense nevertheless.
> > > 
> > > So commit which found real bug(s) was zapped.
> > > 
> > > OK
> > 
> > No, what happened is that the commit was first moved into WIP.x86/debug showing 
> > its work-in-progress status, because it was incomplete and caused bugs:
> > 
> >    https://lore.kernel.org/lkml/20180518073644.GA8593@gmail.com/T/#u
> > 
> > ... and finally, after weeks of inaction I zapped it because I didn't see progress 
> > and you didn't answer my question.
> > 
> > If a fixed patch with updated tooling to detect these crashes before they occur on 
> > live systems is submitted we'll reconsider - it didn't get NAK-ed, it's just 
> > incomplete in the current form.
> 
> Hm, what happened to the objtool patch to detect these at build time?
> Did it not work?
> 
>   https://lore.kernel.org/lkml/20180517134934.eog2fgoby5azq5a7@treble

So that's still incomplete in that doesn't analyze the 32-bit build yet, right?

Thanks,

	Ingo