linux-kernel - Re: [PATCH 4.4 07/40] arm64: ensure __dump_instr() checks addr

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Message-ID: <1510752985.18523.58.camel@codethink.co.uk>
Date:   Wed, 15 Nov 2017 13:36:25 +0000
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org, Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH 4.4 07/40] arm64: ensure __dump_instr() checks addr_limit

On Wed, 2017-11-15 at 13:28 +0000, Ben Hutchings wrote:
> 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@....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@....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.

Only not, because I'm confusing arm and arm64.

Ben.

-- 
Ben Hutchings
Software Developer, Codethink Ltd.