From mboxrd@z Thu Jan  1 00:00:00 1970
From: will.deacon@arm.com (Will Deacon)
Date: Tue, 24 Apr 2018 11:24:09 +0100
Subject: [PATCH] arm64: add sentinel to kpti_safe_list
In-Reply-To: <20180424101954.xyz67zpt6etpm32b@lakrids.cambridge.arm.com>
References: <20180423104133.36395-1-mark.rutland@arm.com>
 <931cba30-91ee-0940-e0f2-a599fbf8eb5a@arm.com>
 <20180424101954.xyz67zpt6etpm32b@lakrids.cambridge.arm.com>
Message-ID: <20180424102409.GD8951@arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Tue, Apr 24, 2018 at 11:19:55AM +0100, Mark Rutland wrote:
> On Mon, Apr 23, 2018 at 05:19:38PM +0100, Suzuki K Poulose wrote:
> > On 23/04/18 11:41, Mark Rutland wrote:
> > > 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@arm.com>
> > > Reported-by: Jan Kiszka <jan.kiszka@siemens.com>
> > > Tested-by: Jan Kiszka <jan.kiszka@siemens.com>
> > > Cc: Catalin Marinas <catalin.marinas@arm.com>
> > > Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
> > > Cc: Will Deacon <will.deacon@arm.com>
> > > ---
> > >   arch/arm64/kernel/cpufeature.c | 1 +
> > >   1 file changed, 1 insertion(+)
> > > 
> > > As discussesd in [1].
> > > 
> > > Mark.
> > > 
> > > [1] https://lkml.kernel.org/r/97d99ad9-c5cf-a4d2-126a-2b39ffead0b3 at web.de
> > > 
> > > 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";
> > 
> > Thanks for the report and the fix.
> > 
> > Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> 
> Cheers!
> 
> Catalin, are you happy to pick this up as a fix for -rc3?

Already got it queued locally.

Will