From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 2 Nov 2017 13:22:35 +0100
Subject: [PATCH] x86/cpuid: Replace set/clear_bit32()
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CVE-2017-5754

Peter pointed out that the set/clear_bit32() variants are broken in various
aspects.

Replace them with open coded set/clear_bit() and type cast
cpu_info::x86_capability as it's done in all other places throughout x86.

Fixes: 0b00de857a64 ("x86/cpuid: Add generic table for CPUID dependencies")
Reported-by: Peter Ziljstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andi Kleen <ak@linux.intel.com>
(cherry picked from commit 06dd688ddda5819025e014b79aea9af6ab475fa2)
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
(cherry picked from commit 3e511952bc3ff9b233d418b0a75a8331deb08171)
Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
---
 arch/x86/kernel/cpu/cpuid-deps.c | 26 +++++++++++---------------
 1 file changed, 11 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
index c21f22d836ad..904b0a3c4e53 100644
--- a/arch/x86/kernel/cpu/cpuid-deps.c
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -62,23 +62,19 @@ const static struct cpuid_dep cpuid_deps[] = {
 	{}
 };
 
-static inline void __clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit)
-{
-	clear_bit32(bit, c->x86_capability);
-}
-
-static inline void __setup_clear_cpu_cap(unsigned int bit)
-{
-	clear_cpu_cap(&boot_cpu_data, bit);
-	set_bit32(bit, cpu_caps_cleared);
-}
-
 static inline void clear_feature(struct cpuinfo_x86 *c, unsigned int feature)
 {
-	if (!c)
-		__setup_clear_cpu_cap(feature);
-	else
-		__clear_cpu_cap(c, feature);
+	/*
+	 * Note: This could use the non atomic __*_bit() variants, but the
+	 * rest of the cpufeature code uses atomics as well, so keep it for
+	 * consistency. Cleanup all of it separately.
+	 */
+	if (!c) {
+		clear_cpu_cap(&boot_cpu_data, feature);
+		set_bit(feature, (unsigned long *)cpu_caps_cleared);
+	} else {
+		clear_bit(feature, (unsigned long *)c->x86_capability);
+	}
 }
 
 /* Take the capabilities and the BUG bits into account */
-- 
2.14.2

