linux-kernel - [PATCH 5/5] x86/crash: make the page that stores the LUKS volume key inaccessible

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Message-Id: <20230601072444.2033855-6-coxu@redhat.com>
Date:   Thu,  1 Jun 2023 15:24:44 +0800
From:   Coiby Xu <coxu@...hat.com>
To:     kexec@...ts.infradead.org
Cc:     Milan Broz <gmazyland@...il.com>,
        Thomas Staudt <tstaudt@...ibm.com>,
        Kairui Song <ryncsn@...il.com>, dm-devel@...hat.com,
        Jan Pazdziora <jpazdziora@...hat.com>,
        Pingfan Liu <kernelfans@...il.com>,
        Baoquan He <bhe@...hat.com>, Dave Young <dyoung@...hat.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Dave Hansen <dave.hansen@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH 5/5] x86/crash: make the page that stores the LUKS volume key inaccessible

This adds an addition layer of protection for the saved copy of LUKS
volume key. Trying to access the saved copy will cause page fault.

Suggested-by: Pingfan Liu <kernelfans@...il.com>
Signed-off-by: Coiby Xu <coxu@...hat.com>
---
 arch/x86/kernel/machine_kexec_64.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 1a3e2c05a8a5..82d1ecb35827 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -546,9 +546,23 @@ static void kexec_mark_crashkres(bool protect)
 	kexec_mark_range(control, crashk_res.end, protect);
 }
 
+static void kexec_mark_luks_volume_key_inaccessible(void)
+{
+	unsigned long start_paddr, end_paddr;
+	unsigned int nr_pages;
+
+	if (kexec_crash_image->luks_volume_key_addr) {
+		start_paddr = kexec_crash_image->luks_volume_key_addr;
+		end_paddr = start_paddr + kexec_crash_image->luks_volume_key_sz - 1;
+		nr_pages = (PAGE_ALIGN(end_paddr) - PAGE_ALIGN_DOWN(start_paddr))/PAGE_SIZE;
+		set_memory_np((unsigned long)phys_to_virt(start_paddr), nr_pages);
+	}
+}
+
 void arch_kexec_protect_crashkres(void)
 {
 	kexec_mark_crashkres(true);
+	kexec_mark_luks_volume_key_inaccessible();
 }
 
 void arch_kexec_unprotect_crashkres(void)
-- 
2.40.1