[PATCH 2/2] x86/kasan: write protect kasan zero shadow
From: Andrey Ryabinin <hidden>
Date: 2016-01-11 12:51:01
Also in:
lkml
Subsystem:
kasan, the rest, x86 architecture (32-bit and 64-bit), x86 mm · Maintainers:
Andrey Ryabinin, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Andy Lutomirski, Peter Zijlstra
After kasan_init() executed, no one is allowed to write to kasan_zero_page, so write protect it. Signed-off-by: Andrey Ryabinin <redacted> --- arch/x86/mm/kasan_init_64.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
index 303e470..1b1110f 100644
--- a/arch/x86/mm/kasan_init_64.c
+++ b/arch/x86/mm/kasan_init_64.c@@ -125,10 +125,16 @@ void __init kasan_init(void) /* * kasan_zero_page has been used as early shadow memory, thus it may - * contain some garbage. Now we can clear it, since after the TLB flush - * no one should write to it. + * contain some garbage. Now we can clear and write protect it, since + * after the TLB flush no one should write to it. */ memset(kasan_zero_page, 0, PAGE_SIZE); + for (i = 0; i < PTRS_PER_PTE; i++) { + pte_t pte = __pte(__pa(kasan_zero_page) | __PAGE_KERNEL_RO); + set_pte(&kasan_zero_pte[i], pte); + } + /* Flush TLBs again to be sure that write protection applied. */ + __flush_tlb_all(); init_task.kasan_depth = 0; pr_info("KernelAddressSanitizer initialized\n");
--
2.4.10
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