Commit-ID: 69e0210fd01ff157d332102219aaf5c26ca8069b Gitweb: http://git.kernel.org/tip/69e0210fd01ff157d332102219aaf5c26ca8069b Author: Andrey Ryabinin <aryabi...@virtuozzo.com> AuthorDate: Mon, 11 Jan 2016 15:51:18 +0300 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Tue, 9 Feb 2016 13:33:14 +0100
x86/kasan: Clear kasan_zero_page after TLB flush 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 <aryabi...@virtuozzo.com> Reviewed-by: Borislav Petkov <b...@suse.de> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Andy Lutomirski <l...@amacapital.net> Cc: Andy Lutomirski <l...@kernel.org> Cc: Borislav Petkov <b...@alien8.de> Cc: Brian Gerst <brge...@gmail.com> Cc: Dave Hansen <dave.han...@linux.intel.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Luis R. Rodriguez <mcg...@suse.com> Cc: Oleg Nesterov <o...@redhat.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Toshi Kani <toshi.k...@hp.com> Cc: linux...@kvack.org Link: http://lkml.kernel.org/r/1452516679-32040-2-git-send-email-aryabi...@virtuozzo.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- arch/x86/mm/kasan_init_64.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c index d470cf2..303e470 100644 --- a/arch/x86/mm/kasan_init_64.c +++ b/arch/x86/mm/kasan_init_64.c @@ -120,11 +120,16 @@ void __init kasan_init(void) kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END), (void *)KASAN_SHADOW_END); - memset(kasan_zero_page, 0, PAGE_SIZE); - load_cr3(init_level4_pgt); __flush_tlb_all(); - 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"); }
