linux-kernel - [PATCH v2 3/3] x86/kexec: Add a sanity check on previous kernel's ima kexec buffer

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Message-ID: <20251229081523.622515-4-harshit.m.mogalapalli@oracle.com>
Date: Mon, 29 Dec 2025 00:15:23 -0800
From: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
To: zohar@...ux.ibm.com
Cc: akpm@...ux-foundation.org, ardb@...nel.org, bp@...en8.de,
        dave.hansen@...ux.intel.com, graf@...zon.com,
        guoweikang.kernel@...il.com, harshit.m.mogalapalli@...cle.com,
        henry.willard@...cle.com, hpa@...or.com, jbohac@...e.cz,
        joel.granados@...nel.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, noodles@...com, paul.x.webb@...cle.com,
        rppt@...nel.org, sohil.mehta@...el.com, sourabhjain@...ux.ibm.com,
        stable@...r.kernel.org, tglx@...utronix.de, x86@...nel.org,
        yifei.l.liu@...cle.com
Subject: [PATCH v2 3/3] x86/kexec: Add a sanity check on previous kernel's ima kexec buffer

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.

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>
---
V1-> V2: Added a line about carrying measure list across kexec based on
suggestion from Mimi Zohar. Made use to the new generic helper
[Suggestion from Borislav]
---
 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 1b2edd07a3e1..383d4a4784f5 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;
 
-- 
2.50.1