perf_event: Remove redundant zero fill

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@freemail.hu>
Cc: Julia Lawall <julia@diku.dk>
Cc: cocci@diku.dk
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <4B086547.5040100@freemail.hu>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index aba8227223008bd53607e8ebbd0c856c01027a19..b26cb03c19140bf2a37aad6a58fac8bb0f4ddafb 100644 (file)
--- 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;