linux-kernel - Re: [PATCH] arm64: kaslr: Reserve size of ARM64_MEMSTART

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Message-ID: <20190413143807.GV11568@sasha-vm>
Date:   Sat, 13 Apr 2019 10:38:07 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Nicolas Boichat <drinkcat@...omium.org>
Cc:     stable@...r.kernel.org, Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "will.deacon@....com" <will.deacon@....com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "markus@...rhumer.com" <markus@...rhumer.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Yueyi Li <liyueyi@...e.com>,
        Guenter Roeck <groeck@...omium.org>
Subject: Re: [PATCH] arm64: kaslr: Reserve size of ARM64_MEMSTART_ALIGN in
 linear region

On Sat, Apr 13, 2019 at 08:41:33PM +0800, Nicolas Boichat wrote:
>Dear stable maintainers,
>
>I encountered a similar issue on a 4.19.33 kernel (Chromium OS). On my
>board, the system would not even be able to boot if KASLR decides to
>map the linear region to the top of the virtual address space. This
>happens every 253 boots on average (there are 0xfd possible random
>offsets, and only the top one fails).
>
>I tried to debug the issue, and it appears physical memory allocated
>for vmemmap and mem_section array would end up at the same location,
>corrupting each other early on boot. I could not figure out exactly
>why this is happening, but in any case, this patch fixes my issue (no
>failure in 744 reboots with 240 unique offsets, and counting...), and
>IMHO the ERR_PTR justification in the commit message is enough to
>warrant inclusion in -stable branches.
>
>The patch below was committed to mainline as:
>commit c8a43c18a97845e7f94ed7d181c11f41964976a2
>    arm64: kaslr: Reserve size of ARM64_MEMSTART_ALIGN in linear region
>
>and should be included in stable branches after this commit:
>Fixes: c031a4213c11a5db ("arm64: kaslr: randomize the linear region")
>i.e. anything after kernel 4.5 (git describe says v4.5-rc4-62-gc031a4213c11a5d).

I've queued it for 4.9-4.19, thanks for the report.

--
Thanks,
Sasha