Patch "x86/init: Clear 'init_level4_pgt' earlier" has been added to the 4.1-stable tree

Patch "x86/init: Clear 'init_level4_pgt' earlier" has been added to the 4.1-stable tree

[gregkh]

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

    x86/init: Clear 'init_level4_pgt' earlier

to the 4.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-init-clear-init_level4_pgt-earlier.patch
and it can be found in the queue-4.1 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 d0f77d4d04b222a817925d33ba3589b190bfa863 Mon Sep 17 00:00:00 2001
From: Andrey Ryabinin <a.ryabinin@samsung.com>
Date: Thu, 2 Jul 2015 12:09:33 +0300
Subject: x86/init: Clear 'init_level4_pgt' earlier

From: Andrey Ryabinin <a.ryabinin@samsung.com>

commit d0f77d4d04b222a817925d33ba3589b190bfa863 upstream.

Currently x86_64_start_kernel() has two KASAN related
function calls. The first call maps shadow to early_level4_pgt,
the second maps shadow to init_level4_pgt.

If we move clear_page(init_level4_pgt) earlier, we could hide
KASAN low level detail from generic x86_64 initialization code.
The next patch will do it.

Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Cc: Alexander Popov <alpopov@ptsecurity.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <adech.fo@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1435828178-10975-2-git-send-email-a.ryabinin@samsung.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/kernel/head64.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -166,6 +166,8 @@ asmlinkage __visible void __init x86_64_
 	/* clear bss before set_intr_gate with early_idt_handler */
 	clear_bss();
 
+	clear_page(init_level4_pgt);
+
 	for (i = 0; i < NUM_EXCEPTION_VECTORS; i++)
 		set_intr_gate(i, early_idt_handler_array[i]);
 	load_idt((const struct desc_ptr *)&idt_descr);
@@ -177,7 +179,6 @@ asmlinkage __visible void __init x86_64_
 	 */
 	load_ucode_bsp();
 
-	clear_page(init_level4_pgt);
 	/* set init_level4_pgt kernel high mapping*/
 	init_level4_pgt[511] = early_level4_pgt[511];
 


Patches currently in stable-queue which might be from a.ryabinin@samsung.com are

queue-4.1/x86-kasan-fix-kasan-shadow-region-page-tables.patch
queue-4.1/x86-kasan-fix-boot-crash-on-amd-processors.patch
queue-4.1/x86-init-clear-init_level4_pgt-earlier.patch
queue-4.1/x86-kasan-flush-tlbs-after-switching-cr3.patch