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authorAndrey Ryabinin <aryabinin@virtuozzo.com>2016-01-11 15:51:18 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-01-05 15:44:27 +0100
commit2b24fe5c57af4d20650e1c3157305459fc5f4afc (patch)
parent755bd549d9328d6d1e949a0a213f9a78e84d11fc (diff)
x86/kasan: Clear kasan_zero_page after TLB flush
commit 69e0210fd01ff157d332102219aaf5c26ca8069b upstream. Currently we clear kasan_zero_page before __flush_tlb_all(). This works with current implementation of native_flush_tlb[_global]() because it doesn't cause do any writes to kasan shadow memory. But any subtle change made in native_flush_tlb*() could break this. Also current code seems doesn't work for paravirt guests (lguest). Only after the TLB flush we can be sure that kasan_zero_page is not used as early shadow anymore (instrumented code will not write to it). So it should cleared it only after the TLB flush. Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com> Reviewed-by: Borislav Petkov <bp@suse.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luis R. Rodriguez <mcgrof@suse.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Toshi Kani <toshi.kani@hp.com> Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/1452516679-32040-2-git-send-email-aryabinin@virtuozzo.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Jamie Iles <jamie.iles@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 8 insertions, 3 deletions
diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
index 4e5ac46adc9d..81ec7c02f968 100644
--- a/arch/x86/mm/kasan_init_64.c
+++ b/arch/x86/mm/kasan_init_64.c
@@ -121,11 +121,16 @@ void __init kasan_init(void)
kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END),
- memset(kasan_zero_page, 0, PAGE_SIZE);
- init_task.kasan_depth = 0;
+ /*
+ * 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.
+ */
+ memset(kasan_zero_page, 0, PAGE_SIZE);
+ init_task.kasan_depth = 0;
pr_info("KernelAddressSanitizer initialized\n");