Commit 3b564968 authored Jan 15, 2014 by Borislav Petkov Committed by H. Peter Anvin Jan 14, 2014

x86, cpu, amd: Add workaround for family 16h, erratum 793



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

Erratum text:

[Revision Guide for AMD Family 16h Models 00h-0Fh Processors,
document 51810 Rev. 3.04 November 2013]

793 Specific Combination of Writes to Write Combined Memory Types and
Locked Instructions May Cause Core Hang

Description

Under a highly specific and detailed set of internal timing
conditions, a locked instruction may trigger a timing sequence whereby
the write to a write combined memory type is not flushed, causing the
locked instruction to stall indefinitely.

Potential Effect on System

Processor core hang.

Suggested Workaround

BIOS should set MSR
C001_1020[15] = 1b.

Fix Planned

No fix planned

[ hpa: updated description, fixed typo in MSR name ]

Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/20140114230711.GS29865@pd.tnic


Tested-by: Aravind Gopalakrishnan <aravind.gopalakrishnan@amd.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

parent a6da83f9

arch/x86/include/uapi/asm/msr-index.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -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

arch/x86/kernel/cpu/amd.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -508,6 +508,16 @@ 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[];

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