[020/114] tracing: Fix an unallocated memory access in function_graph

[Greg KH]

2.6.35-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Shaohua Li <shaohua.li@xxxxxxxxx>

commit 575570f02761bd680ba5731c1dfd4701062e7fb2 upstream.

With CONFIG_DEBUG_PAGEALLOC, I observed an unallocated memory access in
function_graph trace. It appears we find a small size entry in ring buffer,
but we access it as a big size entry. The access overflows the page size
and touches an unallocated page.

Signed-off-by: Shaohua Li <shaohua.li@xxxxxxxxx>
LKML-Reference: <1280217994.32400.76.camel@xxxxxxxxxxxxxxxxxxxxxxx>
[ Added a comment to explain the problem - SDR ]
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 kernel/trace/trace_functions_graph.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -507,7 +507,15 @@ get_return_for_leaf(struct trace_iterato
 			 * if the output fails.
 			 */
 			data->ent = *curr;
-			data->ret = *next;
+			/*
+			 * If the next event is not a return type, then
+			 * we only care about what type it is. Otherwise we can
+			 * safely copy the entire event.
+			 */
+			if (next->ent.type == TRACE_GRAPH_RET)
+				data->ret = *next;
+			else
+				data->ret.ent.type = next->ent.type;
 		}
 	}
 


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