linux-kernel - [PATCH] perf/x86/intel: fix integer overflow when shifting 32 places

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Message-Id: <20170111114310.17928-1-colin.king@canonical.com>
Date:   Wed, 11 Jan 2017 11:43:10 +0000
From:   Colin King <colin.king@...onical.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Stephane Eranian <eranian@...gle.com>,
        Kan Liang <kan.liang@...el.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] perf/x86/intel: fix integer overflow when shifting 32 places

From: Colin Ian King <colin.king@...onical.com>

When x86_pmu.num_counters is set to INTEL_PMC_MAX_GENERIC we end up
with the 32 bit integer constant 1 being shifted 32 places leading to
undefined behaviour.  Fix this by shifting 1ULL instead of 1.

Fixes CoverityScan CID#1192105 ("Bad bit shift operation")

Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 arch/x86/events/intel/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 8613826..d611cab 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3987,7 +3987,7 @@ __init int intel_pmu_init(void)
 		     x86_pmu.num_counters, INTEL_PMC_MAX_GENERIC);
 		x86_pmu.num_counters = INTEL_PMC_MAX_GENERIC;
 	}
-	x86_pmu.intel_ctrl = (1 << x86_pmu.num_counters) - 1;
+	x86_pmu.intel_ctrl = (1ULL << x86_pmu.num_counters) - 1;
 
 	if (x86_pmu.num_counters_fixed > INTEL_PMC_MAX_FIXED) {
 		WARN(1, KERN_ERR "hw perf events fixed %d > max(%d), clipping!",
-- 
2.10.2