Re: [PATCH v8 4/7] kexec: exclude elfcorehdr from the segment digest

Baoquan He
2022-05-11T10:11:54Z

On 05/05/22 at 02:46pm, Eric DeVolder wrote:
> When a crash kernel is loaded via the kexec_file_load syscall, the
> kernel places the various segments (ie crash kernel, crash initrd,
> boot_params, elfcorehdr, purgatory, etc) in memory. For those
> architectures that utilize purgatory, a hash digest of the segments
> is calculated for integrity checking. This digest is embedded into
> the purgatory image prior to placing purgatory in memory.
>
> Since hotplug events cause changes to the elfcorehdr, purgatory
> integrity checking fails (at crash time, and no kdump created).
> As a result, this change explicitly excludes the elfcorehdr segment
> from the list of segments used to create the digest. By doing so,
> this permits changes to the elfcorehdr in response to hotplug events,
> without having to also reload purgatory due to the change to the
> digest.

Remember I acked this one. Seems that is dropped, assuming no change is
made since v7. Anyway,

Acked-by: Baoquan He <bhe@redhat.com>

>
> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
> ---
> kernel/kexec_file.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index 801d0d0a5012..aacdf93c3507 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -765,6 +765,12 @@ static int kexec_calculate_store_digests(struct kimage *image)
> for (j = i = 0; i < image->nr_segments; i++) {
> struct kexec_segment *ksegment;
>
> +#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
> + /* This segment excluded to allow future changes via hotplug */
> + if (image->elfcorehdr_index_valid && (j == image->elfcorehdr_index))
> + continue;
> +#endif
> +
> ksegment = &image->segment[i];
> /*
> * Skip purgatory as it will be modified once we put digest
> --
> 2.27.0
>