Re: [PATCH] mm: huge_memory: don't force huge page alignment on 32 bit

[Yves-Alexis Perez <corsac@debian.org>]

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On Thu, 2024-01-18 at 05:35 -0800, Yang Shi wrote:
> The commit efa7df3e3bb5 ("mm: align larger anonymous mappings on THP
> boundaries") caused two issues [1] [2] reported on 32 bit system or compat
> userspace.
> 
> It doesn't make too much sense to force huge page alignment on 32 bit
> system due to the constrained virtual address space.

Hi people,

sorry for beeing so late. I've looked at this following the OpenSSH issue
(CVE-2024-6387 [1]) and especially the impact on IA-32 installations where
ASLR is apparently broken.

There was a recent thread [2] on oss-security discussing the issue.

Looking at the commit log I think the intention was to fix this both for:
- - 32 bit process running on 64 bit kernels: in_compat_syscall()
- - all processes running on 32 bit kernels: IS_ENABLED(CONFIG_32BIT)

Unfortunately, as far as I can tell, CONFIG_32BIT is not enabled on 32bit x86
kernels. Maybe CONFIG_X86_32 would be the right one there?

[1] https://www.openwall.com/lists/oss-security/2024/07/01/3
[2] https://www.openwall.com/lists/oss-security/2024/07/08/3
- -- 
Yves-Alexis
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