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Date: Tue, 29 May 2018 17:16:09 +0800
From: YaoJun <yaojun8558363@...il.com>
To: kernel-hardening@...ts.openwall.com
Cc: linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org,
jmorris@...ei.org
Subject: [PATCH] mark tramp_pg_dir read-only
To prevent KSMA(Kernel Space Mirroring Attack), it's necessary
to set tramp_pg_dir read-only after initialization.
---
arch/arm64/mm/mmu.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 2dbb2c9f1ec1..964520e4e675 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -551,6 +551,9 @@ static int __init map_entry_trampoline(void)
__create_pgd_mapping(tramp_pg_dir, pa_start, TRAMP_VALIAS, PAGE_SIZE,
prot, pgd_pgtable_alloc, 0);
+ update_mapping_prot(__pa_symbol(tramp_pg_dir), (unsigned long)tramp_pg_dir,
+ PGD_SIZE, PAGE_KERNEL_RO);
+
/* Map both the text and data into the kernel page table */
__set_fixmap(FIX_ENTRY_TRAMP_TEXT, pa_start, prot);
if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
--
2.17.0
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