perf/x86/intel/lbr: Demand proper privileges for PERF_SAMPLE_BRANCH_KERNEL

We should always have proper privileges when requesting kernel
data.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <stable@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: eranian@google.com
Link: http://lkml.kernel.org/r/20130503121256.230745028@chello.nl
[ Fix build error reported by fengguang.wu@intel.com, propagate error code back. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: http://lkml.kernel.org/n/tip-v0x9ky3ahzr6nm3c6ilwrili@git.kernel.org

1 files changed, 10 insertions, 3 deletions

diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
index de341d4ec92a..d978353c939b 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
@@ -310,7 +310,7 @@ void intel_pmu_lbr_read(void)
  * - in case there is no HW filter
  * - in case the HW filter has errata or limitations
  */
-static void intel_pmu_setup_sw_lbr_filter(struct perf_event *event)
+static int intel_pmu_setup_sw_lbr_filter(struct perf_event *event)
 {
         u64 br_type = event->attr.branch_sample_type;
         int mask = 0;
@@ -318,8 +318,11 @@ static void intel_pmu_setup_sw_lbr_filter(struct perf_event *event)
         if (br_type & PERF_SAMPLE_BRANCH_USER)
                 mask |= X86_BR_USER;
 
-        if (br_type & PERF_SAMPLE_BRANCH_KERNEL)
+        if (br_type & PERF_SAMPLE_BRANCH_KERNEL) {
+                if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
+                        return -EACCES;
                 mask |= X86_BR_KERNEL;
+        }
 
         /* we ignore BRANCH_HV here */
 
@@ -339,6 +342,8 @@ static void intel_pmu_setup_sw_lbr_filter(struct perf_event *event)
          * be used by fixup code for some CPU
          */
         event->hw.branch_reg.reg = mask;
+
+        return 0;
 }
 
 /*
@@ -386,7 +391,9 @@ int intel_pmu_setup_lbr_filter(struct perf_event *event)
         /*
          * setup SW LBR filter
          */
-        intel_pmu_setup_sw_lbr_filter(event);
+        ret = intel_pmu_setup_sw_lbr_filter(event);
+        if (ret)
+                return ret;
 
         /*
          * setup HW LBR filter, if any