Re: [PATCH v4 07/10] crash hp: exclude elfcorehdr from the segment digest

[Eric DeVolder]

On 2/22/22 22:00, Baoquan He wrote:
> On 02/09/22 at 02:57pm, 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.
>
> Acked-by: Baoquan He <bhe@xxxxxxxxxx>
Thank you!
eric

> > Signed-off-by: Eric DeVolder <eric.devolder@xxxxxxxxxx>
> > ---
> >   kernel/kexec_file.c | 6 ++++++
> >   1 file changed, 6 insertions(+)
> >
> > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> > index 801d0d0a5012..93bb0c0ce66c 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;
> >   
> > +#ifdef CONFIG_CRASH_HOTPLUG
> > +		/* This segment excluded to allow future changes via hotplug */
> > +		if (image->elf_index_valid && (j == image->elf_index))
> > +			continue;
> > +#endif
> > +
> >   		ksegment = &image->segment[i];
> >   		/*
> >   		 * Skip purgatory as it will be modified once we put digest
> > --
> > 2.27.0