firmware_loader: Strip off \n from customized path

Having helped an user recently figure out why the customized path being
specified was not taken into account landed on a subtle difference
between using:

echo "/xyz/firmware" > /sys/module/firmware_class/parameters/path

which inserts an additional newline which is passed as is down to
fw_get_filesystem_firmware() and ultimately kernel_read_file_from_path()
and fails.

Strip off \n from the customized firmware path such that users do not
run into these hard to debug situations.

Link: https://lore.kernel.org/all/[e-mail]/
Signed-off-by: Florian Fainelli <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/base/firmware_loader/main.c

···
 					     const void *in_buffer))
 {
 	size_t size;
-	int i, len;
+	int i, len, maxlen = 0;
 	int rc = -ENOENT;
-	char *path;
+	char *path, *nt = NULL;
 	size_t msize = INT_MAX;
 	void *buffer = NULL;
 
···
 		if (!fw_path[i][0])
 			continue;
 
-		len = snprintf(path, PATH_MAX, "%s/%s%s",
-			       fw_path[i], fw_priv->fw_name, suffix);
+		/* strip off \n from customized path */
+		maxlen = strlen(fw_path[i]);
+		if (i == 0) {
+			nt = strchr(fw_path[i], '\n');
+			if (nt)
+				maxlen = nt - fw_path[i];
+		}
+
+		len = snprintf(path, PATH_MAX, "%.*s/%s%s",
+			       maxlen, fw_path[i],
+			       fw_priv->fw_name, suffix);
 		if (len >= PATH_MAX) {
 			rc = -ENAMETOOLONG;
 			break;