selftests: uevent filtering: fix return on error in uevent_listener

The ret variable is used to check function return values and assigning
values to it on error has no effect as it is an unused value.

The current implementation uses an additional variable (fret) to return
the error value, which in this case is unnecessary and lead to the above
described misuse. There is no restriction in the current implementation
to always return -1 on error and the actual negative error value can be
returned safely without storing -1 in a specific variable.

Simplify the error checking by using a single variable which always
holds the returned value.

Signed-off-by: Javier Carrasco <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

tools/testing/selftests/uevent/uevent_filtering.c

···
 {
 	int sk_fd, ret;
 	socklen_t sk_addr_len;
-	int fret = -1, rcv_buf_sz = __UEVENT_BUFFER_SIZE;
+	int rcv_buf_sz = __UEVENT_BUFFER_SIZE;
 	uint64_t sync_add = 1;
 	struct sockaddr_nl sk_addr = { 0 }, rcv_addr = { 0 };
 	char buf[__UEVENT_BUFFER_SIZE] = { 0 };
···
 
 	if ((size_t)sk_addr_len != sizeof(sk_addr)) {
 		fprintf(stderr, "Invalid socket address size\n");
+		ret = -1;
 		goto on_error;
 	}
 
···
 	ret = write_nointr(sync_fd, &sync_add, sizeof(sync_add));
 	close(sync_fd);
 	if (ret != sizeof(sync_add)) {
+		ret = -1;
 		fprintf(stderr, "Failed to synchronize with parent process\n");
 		goto on_error;
 	}
 
-	fret = 0;
+	ret = 0;
 	for (;;) {
 		ssize_t r;
 
···
 on_error:
 	close(sk_fd);
 
-	return fret;
+	return ret;
 }
 
 int trigger_uevent(unsigned int times)