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.

Link: https://lkml.kernel.org/r/20250502011246.99238-9-coxu@redhat.com
Signed-off-by: Coiby Xu <coxu@redhat.com>
Suggested-by: Pingfan Liu <kernelfans@gmail.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: "Daniel P. Berrange" <berrange@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Jan Pazdziora <jpazdziora@redhat.com>
Cc: Milan Broz <gmazyland@gmail.com>
Cc: Ondrej Kozina <okozina@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index a68f5a0a9f3708d0d3c9da8beb486b20437dddca..f615fcb6d35de596b35da6941874cc3bfe414753 100644 (file)
--- 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