linux-kernel - [PATCH -v1.2] x86, CPU, AMD: Add workaround for family 16h, erratum 793

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Date:	Wed, 15 Jan 2014 12:10:56 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Henrique de Moraes Holschuh <hmh@....eng.br>,
	X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	Kim Naru <kim.naru@....com>,
	Aravind Gopalakrishnan <aravind.gopalakrishnan@....com>,
	Sherry Hurwitz <sherry.hurwitz@....com>
Subject: [PATCH -v1.2] x86, CPU, AMD: Add workaround for family 16h, erratum
 793

On Tue, Jan 14, 2014 at 04:38:27PM -0800, H. Peter Anvin wrote:
> In file included from
> /home/hpa/kernel/distwork/arch/x86/include/asm/processor.h:20:0,

Finnish!

Well, Boris the dumbass forgot to amend, changes were still in the index
but not committed. This is what I get when I do a couple of things at
the same time. :(

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

This adds the workaround for erratum 793 as a precaution in case not
every BIOS implements it. This addresses CVE-2013-6885.

Signed-off-by: Borislav Petkov <bp@...e.de>
Tested-by: Aravind Gopalakrishnan <aravind.gopalakrishnan@....com>
---
 arch/x86/include/uapi/asm/msr-index.h |  1 +
 arch/x86/kernel/cpu/amd.c             | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/arch/x86/include/uapi/asm/msr-index.h b/arch/x86/include/uapi/asm/msr-index.h
index 37813b5ddc37..59cea185ad1d 100644
--- a/arch/x86/include/uapi/asm/msr-index.h
+++ b/arch/x86/include/uapi/asm/msr-index.h
@@ -184,6 +184,7 @@
 #define MSR_AMD64_PATCH_LOADER		0xc0010020
 #define MSR_AMD64_OSVW_ID_LENGTH	0xc0010140
 #define MSR_AMD64_OSVW_STATUS		0xc0010141
+#define MSR_AMD64_LS_CFG		0xc0011020
 #define MSR_AMD64_DC_CFG		0xc0011022
 #define MSR_AMD64_BU_CFG2		0xc001102a
 #define MSR_AMD64_IBSFETCHCTL		0xc0011030
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 4a48e8bbd857..6ac3a67ad471 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -507,6 +507,16 @@ static void early_init_amd(struct cpuinfo_x86 *c)
 			set_cpu_cap(c, X86_FEATURE_EXTD_APICID);
 	}
 #endif
+
+	/* F16h erratum 793, CVE-2013-6885 */
+	if (c->x86 == 0x16 && c->x86_model <= 0xf) {
+		u64 val;
+
+		rdmsrl(MSR_AMD64_LS_CFG, val);
+		if (!(val & BIT(15)))
+			wrmsrl(MSR_AMD64_LS_CFG, val | BIT(15));
+	}
+
 }
 
 static const int amd_erratum_383[];
-- 
1.8.5.2.192.g7794a68


-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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