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Subject[PATCH v3 7/7] x86/crash: make the page that stores the dm crypt keys inaccessible
Date
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
--
2.44.0

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