Re: [PATCH] arm64: kaslr: Reserve size of ARM64_MEMSTART_ALIGN in linear region

[Sasha Levin]

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