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

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Message-Id: <20180501144604.1cf872e7938bffc01a26349f@linux-foundation.org>
Date:   Tue, 1 May 2018 14:46:04 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Laura Abbott <labbott@...hat.com>
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 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??