On Mon, Oct 20, 2025 at 5:09 PM Pasha Tatashin <[email protected]> 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 <[email protected]> > Reviewed-by: Pratyush Yadav <[email protected]>
Reviewed-by: David Matlack <[email protected]>
