[RFC]ftrace: fix a unallocated memory access in function_graph

From: Shaohua Li
Date: Tue Jul 27 2010 - 04:06:46 EST

With CONFIG_DEBUG_PAGEALLOC, I observed a 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 a page size and touch
a unallocated page.

Signed-off-by: Shaohua Li <shaohua.li@xxxxxxxxx>

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 79f4bac..33b379d 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -507,7 +507,10 @@ get_return_for_leaf(struct trace_iterator *iter,
* if the output fails.
data->ent = *curr;
- data->ret = *next;
+ if (next->ent.type == TRACE_GRAPH_RET)
+ data->ret = *next;
+ else
+ data->ret.ent.type = next->ent.type;

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