x86/kexec: add a sanity check on previous kernel's ima kexec buffer

[ Upstream commit c5489d0 ]

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 cbf9c4b ("of: check previous kernel's ima-kexec-buffer
against memory bounds") do a similar check on x86.

Without carrying the measurement list across kexec, the attestation
would fail.

Link: https://lkml.kernel.org/r/20251231061609.907170-4-harshit.m.mogalapalli@oracle.com
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Fixes: b69a2af ("x86/kexec: Carry forward IMA measurement log on kexec")
Reported-by: Paul Webb <paul.x.webb@oracle.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Betkov <bp@alien8.de>
Cc: guoweikang <guoweikang.kernel@gmail.com>
Cc: Henry Willard <henry.willard@oracle.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Bohac <jbohac@suse.cz>
Cc: Joel Granados <joel.granados@kernel.org>
Cc: Jonathan McDowell <noodles@fb.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Sohil Mehta <sohil.mehta@intel.com>
Cc: Sourabh Jain <sourabhjain@linux.ibm.com>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Yifei Liu <yifei.l.liu@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: harshimogalapalli

arch/x86/kernel/setup.c

@@ -377,9 +377,15 @@ int __init ima_free_kexec_buffer(void)
 
 int __init ima_get_kexec_buffer(void **addr, size_t *size)
 {
+	int ret;
+
 	if (!ima_kexec_buffer_size)
 		return -ENOENT;
 
+	ret = ima_validate_range(ima_kexec_buffer_phys, ima_kexec_buffer_size);
+	if (ret)
+		return ret;
+
 	*addr = __va(ima_kexec_buffer_phys);
 	*size = ima_kexec_buffer_size;