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Message-ID: <1510752482.18523.56.camel@codethink.co.uk>
Subject: Re: [PATCH 4.4 07/40] arm64: ensure __dump_instr() checks addr_limit
From: Ben Hutchings <ben.hutchings@codethink.co.uk>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org, Will Deacon <will.deacon@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>
Date: Wed, 15 Nov 2017 13:28:02 +0000
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On Mon, 2017-11-13 at 19:05 +0000, Ben Hutchings wrote:
> On Mon, 2017-11-06 at 10:44 +0100, Greg Kroah-Hartman wrote:
> > 4.4-stable review patch.  If anyone has any objections, please let me know.
> > 
> > ------------------
> > 
> > > > From: Mark Rutland <mark.rutland@arm.com>
> > 
> > commit 7a7003b1da010d2b0d1dc8bf21c10f5c73b389f1 upstream.
> > 
> > It's possible for a user to deliberately trigger __dump_instr with a
> > chosen kernel address.
> > 
> > Let's avoid problems resulting from this by using get_user() rather than
> > __get_user(), ensuring that we don't erroneously access kernel memory.
> > 
> > Where we use __dump_instr() on kernel text, we already switch to
> > KERNEL_DS, so this shouldn't adversely affect those cases.
> > 
> > Fixes: 60ffc30d5652810d ("arm64: Exception handling")
> 
> [...]
> 
> This seems harmless, but I don't think it will fix the bug in 4.4
> unless you also cherry-pick:
> 
> commit c5cea06be060f38e5400d796e61cfc8c36e52924
> Author: Mark Rutland <mark.rutland@arm.com>
> Date:   Mon Jun 13 11:15:14 2016 +0100
> 
>     arm64: fix dump_instr when PAN and UAO are in use

Oops, now I see you already have that as patch #36.

Ben.

-- 
Ben Hutchings
Software Developer, Codethink Ltd.