perf_event: Remove redundant zero fill

Author: Márton Németh <nm127@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/)

// 
@@
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));
// 

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

Signed-off-by: Márton Németh 
Cc: Julia Lawall 
Cc: cocci@diku.dk
Cc: Peter Zijlstra 
Cc: Paul Mackerras 
LKML-Reference: <4B086547.5040100@freemail.hu>
Signed-off-by: Ingo Molnar 

---
 kernel/perf_event.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
 
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index aba8227..b26cb03 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -3391,7 +3391,7 @@ static void perf_event_comm_event(struct perf_comm_event *comm_event)
 	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;