This is a note to let you know that I've just added the patch titled

x86/kasan: Write protect kasan zero shadow

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: x86-kasan-write-protect-kasan-zero-shadow.patch and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 063fb3e56f6dd29b2633b678b837e1d904200e6f Mon Sep 17 00:00:00 2001

From: Andrey Ryabinin aryabinin@virtuozzo.com Date: Mon, 11 Jan 2016 15:51:19 +0300 Subject: x86/kasan: Write protect kasan zero shadow

From: Andrey Ryabinin aryabinin@virtuozzo.com

commit 063fb3e56f6dd29b2633b678b837e1d904200e6f upstream.

After kasan_init() executed, no one is allowed to write to kasan_zero_page, so write protect it.

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/1452516679-32040-3-git-send-email-aryabinin@virtuoz... Signed-off-by: Ingo Molnar mingo@kernel.org Cc: Guenter Roeck linux@roeck-us.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- arch/x86/mm/kasan_init_64.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)

--- a/arch/x86/mm/kasan_init_64.c +++ b/arch/x86/mm/kasan_init_64.c @@ -126,10 +126,16 @@ 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");

Patches currently in stable-queue which might be from aryabinin@virtuozzo.com are

queue-4.4/x86-kasan-write-protect-kasan-zero-shadow.patch