[PATCH v4 7/7] x86/crash: make the page that stores the dm crypt keys inaccessible

Coiby Xu
2024-05-23T05:05:29Z

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@gmail.com>
Signed-off-by: Coiby Xu <coxu@redhat.com>
---
arch/x86/kernel/machine_kexec_64.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)

diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index b180d8e497c3..fc0a80f4254e 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -545,13 +545,34 @@ static void kexec_mark_crashkres(bool protect)
kexec_mark_range(control, crashk_res.end, protect);
}

+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
--
2.45.0