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Date: Fri, 23 Feb 2018 11:42:02 +0100
From: Jack Wang <jinpu.wang@...fitbricks.com>
To: gregkh@...uxfoundation.org,
stable@...r.kernel.org
Cc: Dan Williams <dan.j.williams@...el.com>,
Thomas Gleixner <tglx@...utronix.de>,
linux-arch@...r.kernel.org,
Tom Lendacky <thomas.lendacky@....com>,
Kees Cook <keescook@...omium.org>,
kernel-hardening@...ts.openwall.com,
Al Viro <viro@...iv.linux.org.uk>,
alan@...ux.intel.com,
David Woodhouse <dwmw@...zon.co.uk>,
Jack Wang <jinpu.wang@...fitbricks.com>
Subject: [stable 4.4 13/29] x86: Introduce barrier_nospec
From: Dan Williams <dan.j.williams@...el.com>
(cherry picked from commit b3d7ad85b80bbc404635dca80f5b129f6242bc7a)
Rename the open coded form of this instruction sequence from
rdtsc_ordered() into a generic barrier primitive, barrier_nospec().
One of the mitigations for Spectre variant1 vulnerabilities is to fence
speculative execution after successfully validating a bounds check. I.e.
force the result of a bounds check to resolve in the instruction pipeline
to ensure speculative execution honors that result before potentially
operating on out-of-bounds data.
No functional changes.
Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
Suggested-by: Andi Kleen <ak@...ux.intel.com>
Suggested-by: Ingo Molnar <mingo@...hat.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-arch@...r.kernel.org
Cc: Tom Lendacky <thomas.lendacky@....com>
Cc: Kees Cook <keescook@...omium.org>
Cc: kernel-hardening@...ts.openwall.com
Cc: gregkh@...uxfoundation.org
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: alan@...ux.intel.com
Link: https://lkml.kernel.org/r/151727415361.33451.9049453007262764675.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
[jwang: cherry pick to 4.4]
Signed-off-by: Jack Wang <jinpu.wang@...fitbricks.com>
---
arch/x86/include/asm/barrier.h | 4 ++++
arch/x86/include/asm/msr.h | 3 +--
2 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h
index b5028e3..814ef83 100644
--- a/arch/x86/include/asm/barrier.h
+++ b/arch/x86/include/asm/barrier.h
@@ -48,6 +48,10 @@ static inline unsigned long array_index_mask_nospec(unsigned long index,
/* Override the default implementation from linux/nospec.h. */
#define array_index_mask_nospec array_index_mask_nospec
+/* Prevent speculative execution past this barrier. */
+#define barrier_nospec() alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC, \
+ "lfence", X86_FEATURE_LFENCE_RDTSC)
+
#ifdef CONFIG_X86_PPRO_FENCE
#define dma_rmb() rmb()
#else
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 77d8b28..5a10ac8 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -147,8 +147,7 @@ static __always_inline unsigned long long rdtsc_ordered(void)
* that some other imaginary CPU is updating continuously with a
* time stamp.
*/
- alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC,
- "lfence", X86_FEATURE_LFENCE_RDTSC);
+ barrier_nospec();
return rdtsc();
}
--
2.7.4
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