Re: [PATCH v2 4/9] crash_dump: Read the number of dm-crypt keys from reserved memory

[Coiby Xu]

On Wed, May 06, 2026 at 07:48:00PM +0530, Sourabh Jain wrote:
> On 02/05/26 05:13, Coiby Xu wrote:
> > In case user adds/deletes the keys by mistake, it's safer to read the
> > number of keys from reserved memory.
> >
> > Fixes: 9ebfa8dcaea7 ("crash_dump: reuse saved dm crypt keys for CPU/memory hot-plugging")
> > Reported-and-Suggested-by: Sourabh Jain <sourabhjain@xxxxxxxxxxxxx>
> > Signed-off-by: Coiby Xu <coiby.xu@xxxxxxxxx>
> > ---
> >  kernel/crash_dump_dm_crypt.c | 36 +++++++++++++++++++++++-------------
> >  1 file changed, 23 insertions(+), 13 deletions(-)
> >
> > diff --git a/kernel/crash_dump_dm_crypt.c b/kernel/crash_dump_dm_crypt.c
> > index 6377ee86ec50..a3e460714d23 100644
> > --- a/kernel/crash_dump_dm_crypt.c
> > +++ b/kernel/crash_dump_dm_crypt.c
> > @@ -88,21 +88,31 @@ static int get_keys_from_kdump_reserved_memory(void)
> >  {
> >  	struct keys_header *keys_header_loaded;
> >  	size_t keys_header_size;
> > -
> > -	keys_header_size = get_keys_header_size(key_count);
> > -	keys_header = kzalloc(keys_header_size, GFP_KERNEL);
> > -	if (!keys_header)
> > -		return -ENOMEM;
> > +	int r = 0;
> >  	arch_kexec_unprotect_crashkres();
> >  	keys_header_loaded = kmap_local_page(pfn_to_page(
> >  		kexec_crash_image->dm_crypt_keys_addr >> PAGE_SHIFT));
> > +	if (keys_header_loaded->total_keys <= 0 ||
> > +	    keys_header_loaded->total_keys > KEY_NUM_MAX) {
> > +		pr_warn("keys_header saved to reserved memory may be corrupt\n");
> > +		r = -EINVAL;
> > +		goto kunmap;
> > +	}
>
> Yes it is good to do a sanity check before using it.
>
> - Sourabh Jain

Thanks! Yeah, better safe than sorry!

--
Best regards,
Coiby