[PATCH 6.19 700/844] x86/kexec: add a sanity check on previous kernel's ima kexec buffer

[Sasha Levin]

From: Harshit Mogalapalli <harshit.m.mogalapalli@xxxxxxxxxx>

[ Upstream commit c5489d04337b47e93c0623e8145fcba3f5739efd ]

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.

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

Link: https://lkml.kernel.org/r/20251231061609.907170-4-harshit.m.mogalapalli@xxxxxxxxxx
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@xxxxxxxxxx>
Fixes: b69a2afd5afc ("x86/kexec: Carry forward IMA measurement log on kexec")
Reported-by: Paul Webb <paul.x.webb@xxxxxxxxxx>
Reviewed-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
Cc: Alexander Graf <graf@xxxxxxxxxx>
Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
Cc: Baoquan He <bhe@xxxxxxxxxx>
Cc: Borislav Betkov <bp@xxxxxxxxx>
Cc: guoweikang <guoweikang.kernel@xxxxxxxxx>
Cc: Henry Willard <henry.willard@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jiri Bohac <jbohac@xxxxxxx>
Cc: Joel Granados <joel.granados@xxxxxxxxxx>
Cc: Jonathan McDowell <noodles@xxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxx>
Cc: Sohil Mehta <sohil.mehta@xxxxxxxxx>
Cc: Sourabh Jain <sourabhjain@xxxxxxxxxxxxx>
Cc: Thomas Gleinxer <tglx@xxxxxxxxxxxxx>
Cc: Yifei Liu <yifei.l.liu@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 arch/x86/kernel/setup.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 1b2edd07a3e17..383d4a4784f5b 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -439,9 +439,15 @@ 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;
 
-- 
2.51.0