Merge remote-tracking branches 'asoc/topic/davinci', 'asoc/topic/drm', 'asoc/topic...

[sfrench/cifs-2.6.git] / kernel / events / core.c

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 6e75a5c9412dee17daabc1cb131bb517ad431207..6c4e523dc1e2e6b53d44bf6a540bc168bcde1eca 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7316,6 +7316,21 @@ int perf_event_account_interrupt(struct perf_event *event)
        return __perf_event_account_interrupt(event, 1);
 }
 
+static bool sample_is_allowed(struct perf_event *event, struct pt_regs *regs)
+{
+       /*
+        * Due to interrupt latency (AKA "skid"), we may enter the
+        * kernel before taking an overflow, even if the PMU is only
+        * counting user events.
+        * To avoid leaking information to userspace, we must always
+        * reject kernel samples when exclude_kernel is set.
+        */
+       if (event->attr.exclude_kernel && !user_mode(regs))
+               return false;
+
+       return true;
+}
+
 /*
  * Generic event overflow handling, sampling.
  */
@@ -7336,6 +7351,12 @@ static int __perf_event_overflow(struct perf_event *event,
 
        ret = __perf_event_account_interrupt(event, throttle);
 
+       /*
+        * For security, drop the skid kernel samples if necessary.
+        */
+       if (!sample_is_allowed(event, regs))
+               return ret;
+
        /*
         * XXX event_limit might not quite work as expected on inherited
         * events