linux-kernel - [tip:x86/asm] x86/asm/64: Clear AC on NMI entries

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Message-ID: <tip-e93c17301ac55321fc18e0f8316e924e58a83c8c@git.kernel.org>
Date:   Thu, 10 Aug 2017 05:22:23 -0700
From:   tip-bot for Andy Lutomirski <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     torvalds@...ux-foundation.org, hpa@...or.com, mingo@...nel.org,
        bp@...en8.de, luto@...nel.org, brgerst@...il.com,
        dvlasenk@...hat.com, peterz@...radead.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de,
        jpoimboe@...hat.com
Subject: [tip:x86/asm] x86/asm/64: Clear AC on NMI entries

Commit-ID:  e93c17301ac55321fc18e0f8316e924e58a83c8c
Gitweb:     http://git.kernel.org/tip/e93c17301ac55321fc18e0f8316e924e58a83c8c
Author:     Andy Lutomirski <luto@...nel.org>
AuthorDate: Mon, 7 Aug 2017 19:43:13 -0700
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 10 Aug 2017 13:13:15 +0200

x86/asm/64: Clear AC on NMI entries

This closes a hole in our SMAP implementation.

This patch comes from grsecurity. Good catch!

Signed-off-by: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: stable@...r.kernel.org
Link: http://lkml.kernel.org/r/314cc9f294e8f14ed85485727556ad4f15bb1659.1502159503.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/entry/entry_64.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index d271fb7..6d078b8 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1211,6 +1211,8 @@ ENTRY(nmi)
 	 * other IST entries.
 	 */
 
+	ASM_CLAC
+
 	/* Use %rdx as our temp variable throughout */
 	pushq	%rdx