linux-kernel - [PATCH 2/2] x86/microcode: Do the family check first

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20180208171204.62005-2-rolf.neugebauer@docker.com>
Date:   Thu,  8 Feb 2018 17:12:04 +0000
From:   Rolf Neugebauer <rolf.neugebauer@...ker.com>
To:     gregkh@...uxfoundation.org
Cc:     bp@...en8.de, zhang.jia@...ux.alibaba.com, tglx@...utronix.de,
        tony.luck@...el.com, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        Borislav Petkov <bp@...e.de>, stable@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Rolf Neugebauer <rolf.neugebauer@...ker.com>
Subject: [PATCH 2/2] x86/microcode: Do the family check first

From: Borislav Petkov <bp@...e.de>

commit 1f161f67a272cc4f29f27934dd3f74cb657eb5c4 upstream with adjustments.

On CPUs like AMD's Geode, for example, we shouldn't even try to load
microcode because they do not support the modern microcode loading
interface.

However, we do the family check *after* the other checks whether the
loader has been disabled on the command line or whether we're running in
a guest.

So move the family checks first in order to exit early if we're being
loaded on an unsupported family.

Reported-and-tested-by: Sven Glodowski <glodi1@...or.de>
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: <stable@...r.kernel.org> # 4.11..
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://bugzilla.suse.com/show_bug.cgi?id=1061396
Link: http://lkml.kernel.org/r/20171012112316.977-1-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: <stable@...r.kernel.org> # 4.4.x
Signed-off-by: Rolf Neugebauer <rolf.neugebauer@...ker.com>
---
 arch/x86/kernel/cpu/microcode/core.c | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 1b3e0aa4c511..ce5f8a2e7ae6 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -94,9 +94,6 @@ static bool __init check_loader_disabled_bsp(void)
 	bool *res = &dis_ucode_ldr;
 #endif
 
-	if (!have_cpuid_p())
-		return *res;
-
 	a = 1;
 	c = 0;
 	native_cpuid(&a, &b, &c, &d);
@@ -138,8 +135,9 @@ void __init load_ucode_bsp(void)
 {
 	int vendor;
 	unsigned int family;
+	bool intel = true;
 
-	if (check_loader_disabled_bsp())
+	if (!have_cpuid_p())
 		return;
 
 	vendor = x86_vendor();
@@ -147,16 +145,27 @@ void __init load_ucode_bsp(void)
 
 	switch (vendor) {
 	case X86_VENDOR_INTEL:
-		if (family >= 6)
-			load_ucode_intel_bsp();
+		if (family < 6)
+			return;
 		break;
+
 	case X86_VENDOR_AMD:
-		if (family >= 0x10)
-			load_ucode_amd_bsp(family);
+		if (family < 0x10)
+			return;
+		intel = false;
 		break;
+
 	default:
-		break;
+		return;
 	}
+
+	if (check_loader_disabled_bsp())
+		return;
+
+	if (intel)
+		load_ucode_intel_bsp();
+	else
+		load_ucode_amd_bsp(family);
 }
 
 static bool check_loader_disabled_ap(void)
-- 
2.16.0