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From 2c1bc0d092e3885ee643c9d5755957a1297b5245 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Fri, 20 Apr 2018 14:23:36 +0200
Subject: [PATCH 19/93] perf/x86/msr: Fix possible Spectre-v1 indexing in the
MSR driver
commit 06ce6e9b6d6c09d4129c6e24a1314a395d816c10 upstream.
> arch/x86/events/msr.c:178 msr_event_init() warn: potential spectre issue 'msr' (local cap)
Userspace controls @attr, sanitize cfg (attr->config) before using it
to index an array.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/events/msr.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/arch/x86/events/msr.c b/arch/x86/events/msr.c
index 4bb3ec6..be0b196 100644
--- a/arch/x86/events/msr.c
+++ b/arch/x86/events/msr.c
@@ -1,4 +1,5 @@
#include <linux/perf_event.h>
+#include <linux/nospec.h>
#include <asm/intel-family.h>
enum perf_msr_id {
@@ -136,9 +137,6 @@ static int msr_event_init(struct perf_event *event)
if (event->attr.type != event->pmu->type)
return -ENOENT;
- if (cfg >= PERF_MSR_EVENT_MAX)
- return -EINVAL;
-
/* unsupported modes and filters */
if (event->attr.exclude_user ||
event->attr.exclude_kernel ||
@@ -149,6 +147,11 @@ static int msr_event_init(struct perf_event *event)
event->attr.sample_period) /* no sampling */
return -EINVAL;
+ if (cfg >= PERF_MSR_EVENT_MAX)
+ return -EINVAL;
+
+ cfg = array_index_nospec((unsigned long)cfg, PERF_MSR_EVENT_MAX);
+
if (!msr[cfg].attr)
return -EINVAL;
--
2.7.4
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