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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Dan Carpenter <dan.carpenter@oracle.com>,
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        Arnaldo Carvalho de Melo <acme@redhat.com>,
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        Thomas Gleixner <tglx@linutronix.de>,
        Vince Weaver <vincent.weaver@maine.edu>,
        Ingo Molnar <mingo@kernel.org>
Subject: [PATCH 4.4 53/56] perf/x86/cstate: Fix possible Spectre-v1 indexing for pkg_msr
Date: Mon, 14 May 2018 08:48:58 +0200
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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Zijlstra <peterz@infradead.org>

commit a5f81290ce475489fa2551c01a07470c1a4c932e upstream.

> arch/x86/events/intel/cstate.c:307 cstate_pmu_event_init() warn: potential spectre issue 'pkg_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/kernel/cpu/perf_event_intel_cstate.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/x86/kernel/cpu/perf_event_intel_cstate.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_cstate.c
@@ -88,6 +88,7 @@
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/perf_event.h>
+#include <linux/nospec.h>
 #include <asm/cpu_device_id.h>
 #include "perf_event.h"
 
@@ -409,6 +410,7 @@ static int cstate_pmu_event_init(struct
 	} else if (event->pmu == &cstate_pkg_pmu) {
 		if (cfg >= PERF_CSTATE_PKG_EVENT_MAX)
 			return -EINVAL;
+		cfg = array_index_nospec((unsigned long)cfg, PERF_CSTATE_PKG_EVENT_MAX);
 		if (!pkg_msr[cfg].attr)
 			return -EINVAL;
 		event->hw.event_base = pkg_msr[cfg].msr;