[for-next][PATCH 1/2] tracing: Use strncpy instead of memcpy when copying comm for hist triggers

[Steven Rostedt]

From: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>

Because there may be random garbage beyond a string's null terminator,
code that might use the entire comm array e.g. histogram keys, can
give unexpected results if that garbage is copied in too, so avoid
that possibility by using strncpy instead of memcpy.

Link: http://lkml.kernel.org/r/1eb9f096a8086c3c82c7fc087c900005143cec54.1551802084.git.tom.zanussi@xxxxxxxxxxxxxxx

Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace_events_hist.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index c7774fa119a7..ca46339f3009 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -2141,7 +2141,7 @@ static inline void save_comm(char *comm, struct task_struct *task)
 		return;
 	}
 
-	memcpy(comm, task->comm, TASK_COMM_LEN);
+	strncpy(comm, task->comm, TASK_COMM_LEN);
 }
 
 static void hist_elt_data_free(struct hist_elt_data *elt_data)
@@ -3557,7 +3557,7 @@ static bool cond_snapshot_update(struct trace_array *tr, void *cond_data)
 	elt_data = context->elt->private_data;
 	track_elt_data = track_data->elt.private_data;
 	if (elt_data->comm)
-		memcpy(track_elt_data->comm, elt_data->comm, TASK_COMM_LEN);
+		strncpy(track_elt_data->comm, elt_data->comm, TASK_COMM_LEN);
 
 	track_data->updated = true;
 
-- 
2.20.1