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Message-ID: <lsq.1520823972.926146860@decadent.org.uk>
Date: Mon, 12 Mar 2018 03:06:12 +0000
From: Ben Hutchings <ben@...adent.org.uk>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC: akpm@...ux-foundation.org,
"Kees Cook" <keescook@...omium.org>,
kernel-hardening@...ts.openwall.com,
"Al Viro" <viro@...iv.linux.org.uk>,
"Linus Torvalds" <torvalds@...ux-foundation.org>,
"Andi Kleen" <ak@...ux.intel.com>,
"Ingo Molnar" <mingo@...hat.com>,
"Dan Williams" <dan.j.williams@...el.com>,
alan@...ux.intel.com,
"Thomas Gleixner" <tglx@...utronix.de>,
"Tom Lendacky" <thomas.lendacky@....com>,
linux-arch@...r.kernel.org, gregkh@...uxfoundation.org
Subject: [PATCH 3.16 54/76] x86: Introduce barrier_nospec
3.16.56-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Dan Williams <dan.j.williams@...el.com>
commit b3d7ad85b80bbc404635dca80f5b129f6242bc7a upstream.
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
[bwh: Backported to 3.16: update rdtsc_barrier() instead of rdtsc_ordered()]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/arch/x86/include/asm/barrier.h
+++ b/arch/x86/include/asm/barrier.h
@@ -48,6 +48,10 @@ static inline unsigned long array_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)
+
/**
* read_barrier_depends - Flush all pending reads that subsequents reads
* depend on.
@@ -174,8 +178,7 @@ do { \
*/
static __always_inline void rdtsc_barrier(void)
{
- alternative(ASM_NOP3, "mfence", X86_FEATURE_MFENCE_RDTSC);
- alternative(ASM_NOP3, "lfence", X86_FEATURE_LFENCE_RDTSC);
+ barrier_nospec();
}
#endif /* _ASM_X86_BARRIER_H */
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