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Date: Mon, 30 Aug 2021 16:59:22 -0700
From: Rick Edgecombe <rick.p.edgecombe@...el.com>
To: dave.hansen@...el.com,
luto@...nel.org,
peterz@...radead.org,
x86@...nel.org,
akpm@...ux-foundation.org,
keescook@...omium.org,
shakeelb@...gle.com,
vbabka@...e.cz,
rppt@...nel.org
Cc: Rick Edgecombe <rick.p.edgecombe@...el.com>,
linux-mm@...ck.org,
linux-hardening@...r.kernel.org,
kernel-hardening@...ts.openwall.com,
ira.weiny@...el.com,
dan.j.williams@...el.com,
linux-kernel@...r.kernel.org
Subject: [RFC PATCH v2 14/19] x86/efi: Toggle table protections when copying
Toggle page table writability when copying page tables in
efi_sync_low_kernel_mappings(). These page tables will not be protected
until after init, but later on they will not be writable.
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
---
arch/x86/platform/efi/efi_64.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 7515e78ef898..7a5c81450fa4 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -116,7 +116,9 @@ void efi_sync_low_kernel_mappings(void)
pgd_k = pgd_offset_k(PAGE_OFFSET);
num_entries = pgd_index(EFI_VA_END) - pgd_index(PAGE_OFFSET);
+ enable_pgtable_write();
memcpy(pgd_efi, pgd_k, sizeof(pgd_t) * num_entries);
+ disable_pgtable_write();
pgd_efi = efi_pgd + pgd_index(EFI_VA_END);
pgd_k = pgd_offset_k(EFI_VA_END);
@@ -124,7 +126,9 @@ void efi_sync_low_kernel_mappings(void)
p4d_k = p4d_offset(pgd_k, 0);
num_entries = p4d_index(EFI_VA_END);
+ enable_pgtable_write();
memcpy(p4d_efi, p4d_k, sizeof(p4d_t) * num_entries);
+ disable_pgtable_write();
/*
* We share all the PUD entries apart from those that map the
@@ -139,13 +143,17 @@ void efi_sync_low_kernel_mappings(void)
pud_k = pud_offset(p4d_k, 0);
num_entries = pud_index(EFI_VA_END);
+ enable_pgtable_write();
memcpy(pud_efi, pud_k, sizeof(pud_t) * num_entries);
+ disable_pgtable_write();
pud_efi = pud_offset(p4d_efi, EFI_VA_START);
pud_k = pud_offset(p4d_k, EFI_VA_START);
num_entries = PTRS_PER_PUD - pud_index(EFI_VA_START);
+ enable_pgtable_write();
memcpy(pud_efi, pud_k, sizeof(pud_t) * num_entries);
+ disable_pgtable_write();
}
/*
--
2.17.1
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