tracing: Use strncpy instead of memcpy when copying comm for hist triggers

tzanussi · rostedt · commit 27242c62b141 · 2019-03-05T12:14:28.000-05:00
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@linux.intel.com Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
diff --git 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;
 

Original file line number	Diff line number	Diff line change
`@@ -2141,7 +2141,7 @@ static inline void save_comm(char comm, struct task_struct task)`
`2141`	`2141`	`return;`
`2142`	`2142`	`}`
`2143`	`2143`
`2144`		`- memcpy(comm, task->comm, TASK_COMM_LEN);`
	`2144`	`+ strncpy(comm, task->comm, TASK_COMM_LEN);`
`2145`	`2145`	`}`
`2146`	`2146`
`2147`	`2147`	`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)`
`3557`	`3557`	`elt_data = context->elt->private_data;`
`3558`	`3558`	`track_elt_data = track_data->elt.private_data;`
`3559`	`3559`	`if (elt_data->comm)`
`3560`		`- memcpy(track_elt_data->comm, elt_data->comm, TASK_COMM_LEN);`
	`3560`	`+ strncpy(track_elt_data->comm, elt_data->comm, TASK_COMM_LEN);`
`3561`	`3561`
`3562`	`3562`	`track_data->updated = true;`
`3563`	`3563`