linux-kernel - [RFC]ftrace: fix a unallocated memory access in function

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Date:	Tue, 27 Jul 2010 16:06:34 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	Ingo Molnar <mingo@...hat.com>, srostedt@...hat.com,
	"Huang, Ying" <ying.huang@...el.com>
Subject: [RFC]ftrace: fix a unallocated memory access in function_graph

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@...el.com>

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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