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

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Message-ID: <ec3c1b29004d1be28563b20765d6a06ccdf18db5.camel@linux.ibm.com>
Date: Mon, 01 Dec 2025 16:43:34 -0500
From: Mimi Zohar <zohar@...ux.ibm.com>
To: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>,
        henry.willard@...cle.com, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar
	 <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen	
 <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin"
 <hpa@...or.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Mike Rapoport
 (Microsoft)" <rppt@...nel.org>,
        Jiri Bohac	 <jbohac@...e.cz>,
        Sourabh Jain
 <sourabhjain@...ux.ibm.com>,
        Guo Weikang	 <guoweikang.kernel@...il.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Joel Granados	
 <joel.granados@...nel.org>,
        Alexander Graf <graf@...zon.com>,
        Sohil Mehta	
 <sohil.mehta@...el.com>,
        Jonathan McDowell <noodles@...com>, linux-kernel@...r.kernel.org
Cc: yifei.l.liu@...cle.com, stable@...r.kernel.org,
        Paul Webb
	 <paul.x.webb@...cle.com>
Subject: Re: [PATCH] x86/kexec: Add a sanity check on previous kernel's ima
 kexec buffer

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.

> > 
> > Cc: stable@...r.kernel.org
> > Fixes: b69a2afd5afc ("x86/kexec: Carry forward IMA measurement log on kexec")
> > Reported-by: Paul Webb <paul.x.webb@...cle.com>
> > Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>

Tested-by: Mimi Zohar <zohar@...ux.ibm.com>
>