1 files changed, 4 insertions, 0 deletions

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index d76e3112d386..7669afe82cc7 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1422,6 +1422,7 @@ struct perf_output_handle {
         struct perf_counter     *counter;
         struct perf_mmap_data   *data;
         unsigned int            offset;
+        unsigned int            head;
         int                     wakeup;
 };
 
@@ -1447,6 +1448,7 @@ static int perf_output_begin(struct perf_output_handle *handle,
         handle->counter = counter;
         handle->data    = data;
         handle->offset  = offset;
+        handle->head    = head;
         handle->wakeup  = (offset >> PAGE_SHIFT) != (head >> PAGE_SHIFT);
 
         return 0;
@@ -1485,6 +1487,8 @@ static void perf_output_copy(struct perf_output_handle *handle,
         } while (len);
 
         handle->offset = offset;
+
+        WARN_ON_ONCE(handle->offset > handle->head);
 }
 
 #define perf_output_put(handle, x) \