linux-kernel - Re: BUG: KASAN: global-out-of-bounds in unmap_kernel_at

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Message-ID: <20180423102909.ra2n6tqvwcn7oash@lakrids.cambridge.arm.com>
Date:   Mon, 23 Apr 2018 11:29:09 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Jan Kiszka <jan.kiszka@....de>
Cc:     linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        will.deacon@....com, catalin.marinas@....com,
        suzuki.poulose@....com
Subject: Re: BUG: KASAN: global-out-of-bounds in
 unmap_kernel_at_el0+0x70/0x1a0

On Mon, Apr 23, 2018 at 07:00:52AM +0200, Jan Kiszka wrote:
> On 2018-04-22 21:06, Mark Rutland wrote:

> > Does the below help?

> > From ade322407e3d6d1f50e558ebd50d2c1c7bd811c2 Mon Sep 17 00:00:00 2001
> > From: Mark Rutland <mark.rutland@....com>
> > Date: Sun, 22 Apr 2018 19:58:08 +0100
> > Subject: [PATCH] arm64: add sentinel to kpti_safe_list
> > 
> > We're missing a sentinel entry in kpti_safe_list. Thus is_midr_in_range_list()
> > can walk past the end of kpti_safe_list. Depending on the contents of memory,
> > this could erroneously match a CPU's MIDR, cause a data abort, or other bad
> > outcomes.
> > 
> > Add the sentinel entry to avoid this.
> > 
> > Fixes: be5b299830c63ed7 ("arm64: capabilities: Add support for checks based on a list of MIDRs")
> > Signed-off-by: Mark Rutland <mark.rutland@....com>
> > Reported-by: Jan Kiszka <jan.kiszka@....de>
> > Cc: Catalin Marinas <catalin.marinas@....com>
> > Cc: Suzuki K Poulose <suzuki.poulose@....com>
> > Cc: Will Deacon <will.deacon@....com>
> > ---
> >  arch/arm64/kernel/cpufeature.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> > index 536d572e5596..9d1b06d67c53 100644
> > --- a/arch/arm64/kernel/cpufeature.c
> > +++ b/arch/arm64/kernel/cpufeature.c
> > @@ -868,6 +868,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
> >  	static const struct midr_range kpti_safe_list[] = {
> >  		MIDR_ALL_VERSIONS(MIDR_CAVIUM_THUNDERX2),
> >  		MIDR_ALL_VERSIONS(MIDR_BRCM_VULCAN),
> > +		{ /* sentinel */ }
> >  	};
> >  	char const *str = "command line option";
> >  
> > 
> 
> Jep, all fine now!

Cool. Can I take that as a Tested-by?

Mark.