diff mbox

[3.13.y-ckt,stable] Patch "x86/nmi/64: Remove asm code that saves cr2" has been added to staging queue

Message ID 1438290232-27816-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa July 30, 2015, 9:03 p.m. UTC 
This is a note to let you know that I have just added a patch titled

    x86/nmi/64: Remove asm code that saves cr2

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.y-ckt25.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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From 522d486b0f56ca0f33962148819d647118f12c10 Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <luto@kernel.org>
Date: Fri, 10 Jul 2015 12:03:34 -0700
Subject: x86/nmi/64: Remove asm code that saves cr2

commit 0e181bb58143cb4a2e8f01c281b0816cd0e4798e upstream.

Now that do_nmi saves cr2, we don't need to save it in asm.

This is a prerequisity for the fix for CVE-2015-3290.

Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
[bwh: Backported to 4.0: adjust filename, context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Acked-by: John Johansen <john.johansen@canonical.com>
Acked-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 arch/x86/kernel/entry_64.S | 18 ------------------
 1 file changed, 18 deletions(-)

--
1.9.1
diff mbox

Patch

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index ed0f923..2cd55a8 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1919,29 +1919,11 @@  end_repeat_nmi:
 	call save_paranoid
 	DEFAULT_FRAME 0

-	/*
-	 * Save off the CR2 register. If we take a page fault in the NMI then
-	 * it could corrupt the CR2 value. If the NMI preempts a page fault
-	 * handler before it was able to read the CR2 register, and then the
-	 * NMI itself takes a page fault, the page fault that was preempted
-	 * will read the information from the NMI page fault and not the
-	 * origin fault. Save it off and restore it if it changes.
-	 * Use the r12 callee-saved register.
-	 */
-	movq %cr2, %r12
-
 	/* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */
 	movq %rsp,%rdi
 	movq $-1,%rsi
 	call do_nmi

-	/* Did the NMI take a page fault? Restore cr2 if it did */
-	movq %cr2, %rcx
-	cmpq %rcx, %r12
-	je 1f
-	movq %r12, %cr2
-1:
-
 	testl %ebx,%ebx				/* swapgs needed? */
 	jnz nmi_restore
 nmi_swapgs: