user_events: Fix potential uninitialized pointer while parsing field

Ensure name is initialized by default to NULL to prevent possible edge
cases that could lead to it being left uninitialized. Add an explicit
check for NULL name to ensure edge boundaries.

Link: https://lore.kernel.org/bpf/20220224105334.GA2248@kili/
Link: https://lore.kernel.org/linux-trace-devel/20220224181637.2129-1-beaub@linux.microsoft.com

Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Author: beaubelgrave

kernel/trace/trace_events_user.c

@@ -362,6 +362,8 @@ static int user_event_parse_field(char *field, struct user_event *user,
 	*field++ = '\0';
 	depth++;
 parse:
+	name = NULL;
+
 	while ((part = strsep(&field, " ")) != NULL) {
 		switch (depth++) {
 		case FIELD_DEPTH_TYPE:
@@ -382,7 +384,7 @@ static int user_event_parse_field(char *field, struct user_event *user,
 		}
 	}
 
-	if (depth < FIELD_DEPTH_SIZE)
+	if (depth < FIELD_DEPTH_SIZE || !name)
 		return -EINVAL;
 
 	if (depth == FIELD_DEPTH_SIZE)