linux-kernel - Re: [PATCH] proc/kcore: Don't bounds check against address 0

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Message-ID: <4db64722-47b5-767c-4090-bdd9c1522e96@redhat.com>
Date:   Tue, 1 May 2018 15:26:00 -0700
From:   Laura Abbott <labbott@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Dave Anderson <anderson@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH] proc/kcore: Don't bounds check against address 0

On 05/01/2018 02:46 PM, Andrew Morton wrote:
> On Tue,  1 May 2018 13:11:43 -0700 Laura Abbott <labbott@...hat.com> wrote:
> 
>> The existing kcore code checks for bad addresses against
>> __va(0) with the assumption that this is the lowest address
>> on the system. This may not hold true on some systems (e.g.
>> arm64) and produce overflows and crashes. Switch to using
>> other functions to validate the address range.
>>
>> Tested-by: Dave Anderson <anderson@...hat.com>
>> Signed-off-by: Laura Abbott <labbott@...hat.com>
>> ---
>> I took your previous comments as a tested by, please let me know if that
>> was wrong. This should probably just go through -mm. I don't think this
>> is necessary for stable but I can request it later if necessary.
> 
> I'm surprised.  "overflows and crashes" sounds rather serious??
> 

It's currently only seen on arm64 and it's not clear if anyone
wants to use that particular combination on a stable release.
I think a better phrase is "this is not urgent for stable".

Thanks,
Laura