[Cocci] [PATCH 3/4] perf_event: remove redundant zero fill

[Németh Márton]

From: Márton Németh <nm127 at freemail.hu>

The buffer is first zeroed out by memset(). Then strncpy() is used to
fill the content. The strncpy() function also pads the string till the
end of the specified length, which is redundant. The strncpy() does not
ensures that the string will be properly closed with 0. Use strlcpy()
instead.

The semantic match that finds this kind of pattern is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression buffer;
expression size;
expression str;
@@
	memset(buffer, 0, size);
	...
-	strncpy(
+	strlcpy(
	buffer, str, sizeof(buffer)
	);
@@
expression buffer;
expression size;
expression str;
@@
	memset(&buffer, 0, size);
	...
-	strncpy(
+	strlcpy(
	&buffer, str, sizeof(buffer));
@@
expression buffer;
identifier field;
expression size;
expression str;
@@
	memset(buffer, 0, size);
	...
-	strncpy(
+	strlcpy(
	buffer->field, str, sizeof(buffer->field)
	);
@@
expression buffer;
identifier field;
expression size;
expression str;
@@
	memset(&buffer, 0, size);
	...
-	strncpy(
+	strlcpy(
	buffer.field, str, sizeof(buffer.field));
// </smpl>

On strncpy() vs strlcpy() see http://www.gratisoft.us/todd/papers/strlcpy.html .

Signed-off-by: Márton Németh <nm127 at freemail.hu>
---
diff -u -p a/kernel/perf_event.c b/kernel/perf_event.c
--- a/kernel/perf_event.c 2009-11-14 07:06:52.000000000 +0100
+++ b/kernel/perf_event.c 2009-11-21 22:15:26.000000000 +0100
@@ -3367,7 +3367,7 @@ static void perf_event_comm_event(struct
 	char comm[TASK_COMM_LEN];

 	memset(comm, 0, sizeof(comm));
-	strncpy(comm, comm_event->task->comm, sizeof(comm));
+	strlcpy(comm, comm_event->task->comm, sizeof(comm));
 	size = ALIGN(strlen(comm)+1, sizeof(u64));

 	comm_event->comm = comm;