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

[Coiby Xu]

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@xxxxxxxxx>
Signed-off-by: Coiby Xu <coxu@xxxxxxxxxx>
---
 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