linux-kernel - Re: [PATCH v3 3/3] liveupdate: kho: allocate metadata directly from the buddy allocator

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CALzav=fa0rxnf-ufDmV0uhA+zhoOB2vp9ksfNpeE0amxnLt0jw@mail.gmail.com>
Date: Mon, 27 Oct 2025 16:04:42 -0700
From: David Matlack <dmatlack@...gle.com>
To: Pasha Tatashin <pasha.tatashin@...een.com>
Cc: akpm@...ux-foundation.org, brauner@...nel.org, corbet@....net, 
	graf@...zon.com, jgg@...pe.ca, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, linux-mm@...ck.org, masahiroy@...nel.org, 
	ojeda@...nel.org, pratyush@...nel.org, rdunlap@...radead.org, rppt@...nel.org, 
	tj@...nel.org, jasonmiu@...gle.com, skhawaja@...gle.com
Subject: Re: [PATCH v3 3/3] liveupdate: kho: allocate metadata directly from
 the buddy allocator

On Mon, Oct 20, 2025 at 5:09 PM Pasha Tatashin
<pasha.tatashin@...een.com> wrote:
>
> KHO allocates metadata for its preserved memory map using the slab
> allocator via kzalloc(). This metadata is temporary and is used by the
> next kernel during early boot to find preserved memory.
>
> A problem arises when KFENCE is enabled. kzalloc() calls can be
> randomly intercepted by kfence_alloc(), which services the allocation
> from a dedicated KFENCE memory pool. This pool is allocated early in
> boot via memblock.
>
> When booting via KHO, the memblock allocator is restricted to a "scratch
> area", forcing the KFENCE pool to be allocated within it. This creates a
> conflict, as the scratch area is expected to be ephemeral and
> overwriteable by a subsequent kexec. If KHO metadata is placed in this
> KFENCE pool, it leads to memory corruption when the next kernel is
> loaded.
>
> To fix this, modify KHO to allocate its metadata directly from the buddy
> allocator instead of slab.
>
> Fixes: fc33e4b44b27 ("kexec: enable KHO support for memory preservation")
> Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>
> Reviewed-by: Pratyush Yadav <pratyush@...nel.org>

Reviewed-by: David Matlack <dmatlack@...gle.com>