Date: Fri, 15 Jan 2016 11:23:07 +0000 From: Mark Rutland <mark.rutland@....com> To: Ard Biesheuvel <ard.biesheuvel@...aro.org> Cc: Kees Cook <keescook@...omium.org>, Arnd Bergmann <arnd@...db.de>, kernel-hardening@...ts.openwall.com, Sharma Bhupesh <bhupesh.sharma@...escale.com>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Leif Lindholm <leif.lindholm@...aro.org>, Stuart Yoder <stuart.yoder@...escale.com>, Marc Zyngier <marc.zyngier@....com>, Christoffer Dall <christoffer.dall@...aro.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org> Subject: Re: [PATCH v3 07/21] arm64: move kernel image to base of vmalloc area On Fri, Jan 15, 2016 at 10:54:26AM +0100, Ard Biesheuvel wrote: > On 14 January 2016 at 19:57, Mark Rutland <mark.rutland@....com> wrote: > > On Wed, Jan 13, 2016 at 01:51:10PM +0000, Mark Rutland wrote: > >> On Wed, Jan 13, 2016 at 09:39:41AM +0100, Ard Biesheuvel wrote: > >> > If I remove the rounding, I get false positive kasan errors which I > >> > have not quite diagnosed yet, but are probably due to the fact that > >> > the rounding performed by vmemmap_populate() goes in the wrong > >> > direction. > > > > As far as I can see, it implicitly rounds the base down and end up to > > SWAPPER_BLOCK_SIZE granularity. > > > > I can see that it might map too much memory, but I can't see why that > > should trigger KASAN failures. Regardless of what was mapped KASAN > > should stick to the region it cares about, and everything else should > > stay out of that. > > > > When do you see the failures, and are they in any way consistent? > > > > Do you have an example to hand? > > > > For some reason, this issue has evaporated, i.e., I can no longer > reproduce it on my WIP v4 branch. > So I will remove the rounding. Ok. I'll let you know if I stumble across anything that looks like a potential cause of the KASAN failures, and I'll try to give v4 a go at some point soon. Thanks, Mark.
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