linux-kernel - [PATCH v8 7/7] x86/crash: make the page that stores the dm crypt keys inaccessible

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Message-ID: <20250207081358.129794-1-coxu@redhat.com>
Date: Fri,  7 Feb 2025 16:13:58 +0800
From: Coiby Xu <coxu@...hat.com>
To: kexec@...ts.infradead.org
Cc: Ondrej Kozina <okozina@...hat.com>,
	Milan Broz <gmazyland@...il.com>,
	Thomas Staudt <tstaudt@...ibm.com>,
	Daniel P . Berrangé <berrange@...hat.com>,
	Kairui Song <ryncsn@...il.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 v8 7/7] x86/crash: make the page that stores the dm crypt keys inaccessible

This adds an addition layer of protection for the saved copy of dm
crypt 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 | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index a68f5a0a9f37..f615fcb6d35d 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -598,13 +598,35 @@ static void kexec_mark_crashkres(bool protect)
 	kexec_mark_range(control, crashk_res.end, protect);
 }
 
+/* make the memory storing dm crypt keys in/accessible */
+static void kexec_mark_dm_crypt_keys(bool protect)
+{
+	unsigned long start_paddr, end_paddr;
+	unsigned int nr_pages;
+
+	if (kexec_crash_image->dm_crypt_keys_addr) {
+		start_paddr = kexec_crash_image->dm_crypt_keys_addr;
+		end_paddr = start_paddr + kexec_crash_image->dm_crypt_keys_sz - 1;
+		nr_pages = (PAGE_ALIGN(end_paddr) - PAGE_ALIGN_DOWN(start_paddr))/PAGE_SIZE;
+		if (protect)
+			set_memory_np((unsigned long)phys_to_virt(start_paddr), nr_pages);
+		else
+			__set_memory_prot(
+				(unsigned long)phys_to_virt(start_paddr),
+				nr_pages,
+				__pgprot(_PAGE_PRESENT | _PAGE_NX | _PAGE_RW));
+	}
+}
+
 void arch_kexec_protect_crashkres(void)
 {
 	kexec_mark_crashkres(true);
+	kexec_mark_dm_crypt_keys(true);
 }
 
 void arch_kexec_unprotect_crashkres(void)
 {
+	kexec_mark_dm_crypt_keys(false);
 	kexec_mark_crashkres(false);
 }
 #endif
-- 
2.48.1