Re: [PATCH] x86/kexec: Add a sanity check on previous kernel's ima kexec buffer

[Ard Biesheuvel]

On Mon, 1 Dec 2025 at 22:43, Mimi Zohar <zohar@xxxxxxxxxxxxx> wrote:
>
> On Mon, 2025-12-01 at 15:03 +0530, Harshit Mogalapalli wrote:
> > Hi all,
> >
> > On 13/11/25 01:00, Harshit Mogalapalli wrote:
> > > When the second-stage kernel is booted via kexec with a limiting command
> > > line such as "mem=<size>", the physical range that contains the carried
> > > over IMA measurement list may fall outside the truncated RAM leading to
> > > a kernel panic.
> > >
> > >      BUG: unable to handle page fault for address: ffff97793ff47000
> > >      RIP: ima_restore_measurement_list+0xdc/0x45a
> > >      #PF: error_code(0x0000) – not-present page
> > >
> > > Other architectures already validate the range with page_is_ram(), as
> > > done in commit: cbf9c4b9617b ("of: check previous kernel's
> > > ima-kexec-buffer against memory bounds") do a similar check on x86.
>
> It should be obvious that without carrying the measurement list across kexec,
> that attestation will fail.  Please mentioned it here in the patch description.
>

Couldn't we just use memremap() and be done with it? That will use the
direct map if the memory is mapped, or vmap() it otherwise.