linux-kernel - [tip:perf/urgent] tracing: Fix an unallocated memory access in function

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Message-ID: <tip-575570f02761bd680ba5731c1dfd4701062e7fb2@git.kernel.org>
Date:	Mon, 16 Aug 2010 17:30:40 GMT
From:	tip-bot for Shaohua Li <shaohua.li@...el.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	rostedt@...dmis.org, stable@...nel.org, shaohua.li@...el.com,
	tglx@...utronix.de
Subject: [tip:perf/urgent] tracing: Fix an unallocated memory access in function_graph

Commit-ID:  575570f02761bd680ba5731c1dfd4701062e7fb2
Gitweb:     http://git.kernel.org/tip/575570f02761bd680ba5731c1dfd4701062e7fb2
Author:     Shaohua Li <shaohua.li@...el.com>
AuthorDate: Tue, 27 Jul 2010 16:06:34 +0800
Committer:  Steven Rostedt <rostedt@...dmis.org>
CommitDate: Fri, 6 Aug 2010 12:19:15 -0400

tracing: Fix an unallocated memory access in function_graph

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.

Cc: <stable@...nel.org>
Signed-off-by: Shaohua Li <shaohua.li@...el.com>
LKML-Reference: <1280217994.32400.76.camel@...10-desk.sh.intel.com>
[ Added a comment to explain the problem - SDR ]
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
---
 kernel/trace/trace_functions_graph.c |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 79f4bac..b4c179a 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -507,7 +507,15 @@ get_return_for_leaf(struct trace_iterator *iter,
 			 * 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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