On Fri, Dec 19, 2025 at 02:12:09AM -0500, Pasha Tatashin wrote:
> If the previous kernel enabled KHO but did not call kho_finalize()
> (e.g., CONFIG_LIVEUPDATE=n or userspace skipped the finalization step),
> the 'preserved-memory-map' property in the FDT remains empty/zero.
>
> Previously, kho_populate() would succeed regardless of the memory map's
> state, reserving the incoming scratch regions in memblock. However,
> kho_memory_init() would later fail to deserialize the empty map. By that
> time, the scratch regions were already registered, leading to partial
> initialization and subsequent list corruption (double-free) during
> kho_init().
>
> Move the validation of the preserved memory map earlier into
> kho_populate(). If the memory map is empty/NULL:
> 1. Abort kho_populate() immediately with -ENOENT.
> 2. Do not register or reserve the incoming scratch memory, allowing the new
> kernel to reclaim those pages as standard free memory.
> 3. Leave the global 'kho_in' state uninitialized.
>
> Consequently, kho_memory_init() sees no active KHO context
> (kho_in.mem_chunks_phys is 0) and falls back to kho_reserve_scratch(),
> allocating fresh scratch memory as if it were a standard cold boot.
>
> Fixes: de51999e687c ("kho: allow memory preservation state updates after
> finalization")
> Reported-by: Ricardo Neri <[email protected]>
> Closes:
> https://lore.kernel.org/all/[email protected]
> Signed-off-by: Pasha Tatashin <[email protected]>
> Reviewed-by: Mike Rapoport (Microsoft) <[email protected]>
Thanks for the patch (and fixing my e-mail ;)). This fixes the reported
issue and now I can kexec reboot correctly with an empty, unfinalized KHO
FDT.
Tested-by: Ricardo Neri <[email protected]>
