This is a note to let you know that I've just added the patch titled
x86, cpu, amd: Add workaround for family 16h, erratum 793
to the 3.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-cpu-amd-add-workaround-for-family-16h-erratum-793.patch
and it can be found in the queue-3.13 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3b56496865f9f7d9bcb2f93b44c63f274f08e3b6 Mon Sep 17 00:00:00 2001
From: Borislav Petkov <bp@xxxxxxx>
Date: Wed, 15 Jan 2014 00:07:11 +0100
Subject: x86, cpu, amd: Add workaround for family 16h, erratum 793
From: Borislav Petkov <bp@xxxxxxx>
commit 3b56496865f9f7d9bcb2f93b44c63f274f08e3b6 upstream.
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@xxxxxxx>
Link: http://lkml.kernel.org/r/20140114230711.GS29865@xxxxxxx
Tested-by: Aravind Gopalakrishnan <aravind.gopalakrishnan@xxxxxxx>
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/uapi/asm/msr-index.h | 1 +
arch/x86/kernel/cpu/amd.c | 10 ++++++++++
2 files changed, 11 insertions(+)
--- 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
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -508,6 +508,16 @@ static void early_init_amd(struct cpuinf
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[];
Patches currently in stable-queue which might be from bp@xxxxxxx are
queue-3.13/x86-efi-fix-off-by-one-bug-in-efi-boot-services-reservation.patch
queue-3.13/rtc-cmos-add-an-alarm-disable-quirk.patch
queue-3.13/x86-cpu-amd-add-workaround-for-family-16h-erratum-793.patch
queue-3.13/e752x_edac-fix-pci_dev-usage-count.patch
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