ring_buffer: Off-by-one and duplicate events in ring_buffer_read_page

[mv-sheeva.git] / kernel / trace / ring_buffer.c

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 9ed509a015d81a69cd452b3697658dd7fde9cb71..bd1c35a4fbccf31c0531f0667545011f704c561f 100644 (file)
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -3853,6 +3853,13 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
 
                /* Need to copy one event at a time */
                do {
+                       /* We need the size of one event, because
+                        * rb_advance_reader only advances by one event,
+                        * whereas rb_event_ts_length may include the size of
+                        * one or two events.
+                        * We have already ensured there's enough space if this
+                        * is a time extend. */
+                       size = rb_event_length(event);
                        memcpy(bpage->data + pos, rpage->data + rpos, size);
 
                        len -= size;
@@ -3867,7 +3874,7 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
                        event = rb_reader_event(cpu_buffer);
                        /* Always keep the time extend and data together */
                        size = rb_event_ts_length(event);
-               } while (len > size);
+               } while (len >= size);
 
                /* update bpage */
                local_set(&bpage->commit, pos);