linux-kernel - [PATCH 3.16 106/294] x86/asm/64: Clear AC on NMI entries

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Message-ID: <lsq.1510009382.536079999@decadent.org.uk>
Date:   Mon, 06 Nov 2017 23:03:02 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Peter Zijlstra" <peterz@...radead.org>,
        "H. Peter Anvin" <hpa@...or.com>, "Borislav Petkov" <bp@...en8.de>,
        "Brian Gerst" <brgerst@...il.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Josh Poimboeuf" <jpoimboe@...hat.com>,
        "Denys Vlasenko" <dvlasenk@...hat.com>,
        "Ingo Molnar" <mingo@...nel.org>,
        "Andy Lutomirski" <luto@...nel.org>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>
Subject: [PATCH 3.16 106/294] x86/asm/64: Clear AC on NMI entries

3.16.50-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Andy Lutomirski <luto@...nel.org>

commit e93c17301ac55321fc18e0f8316e924e58a83c8c upstream.

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>
Link: http://lkml.kernel.org/r/314cc9f294e8f14ed85485727556ad4f15bb1659.1502159503.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
[bwh: Backported to 3.16: adjust filename, context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/kernel/entry_64.S | 2 ++
 1 file changed, 2 insertions(+)

--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1476,6 +1476,8 @@ ENTRY(nmi)
 	 * other IST entries.
 	 */
 
+	ASM_CLAC
+
 	/* Use %rdx as out temp variable throughout */
 	pushq_cfi %rdx
 	CFI_REL_OFFSET rdx, 0