linux-kernel - Re: [PATCH] arm64: kasan: clear stale stack poison

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Message-ID: <20160218180353.GG16883@arm.com>
Date:	Thu, 18 Feb 2016 18:03:54 +0000
From:	Will Deacon <will.deacon@....com>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	Mark Rutland <mark.rutland@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>, mingo@...nel.org,
	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	akpm@...ux-foundation.org, hpa@...ux.intel.com, tglx@...utronix.de
Subject: Re: [PATCH] arm64: kasan: clear stale stack poison

On Thu, Feb 18, 2016 at 05:54:47PM +0000, Catalin Marinas wrote:
> On Thu, Feb 18, 2016 at 05:27:38PM +0000, Mark Rutland wrote:
> > @@ -145,6 +146,7 @@ ENTRY(cpu_resume_mmu)
> >  ENDPROC(cpu_resume_mmu)
> >  	.popsection
> >  cpu_resume_after_mmu:
> > +	kasan_unpoison_stack 96
> 
> I don't think the 96 here is needed since we populate the stack in
> assembly (__cpu_suspend_enter) and unwind it again still in assembly
> (cpu_resume_after_mmu), so no KASAN shadow writes/reads.
> 
> Otherwise the patch looks fine.

I'd much rather it was written in C -- is there a reason we can't do
that if we use a separate compilation unit where the compiler will
honour the fno-sanitize flag?

Will