net: dsa: ensure port names are NULL-terminated after DSA_PORT_NAME_LENGTH truncation

strncpy() simply bails out when copying a source string whose size
exceeds the destination string size, potentially leaving the destination
string unterminated.

One possible way to address is to pass DSA_PORT_NAME_LENGTH - 1 and a
previously zero-initialized destination string, but this is more
difficult to maintain.

The chosen alternative is to use strlcpy(), which properly limits the
copy len in the (srclen >= size) case to "size - 1", and which is also
more efficient than the strncpy() byte-by-byte implementation by using
memcpy. The destination string returned by strlcpy() is always NULL
terminated.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
diff --git a/net/dsa-uclass.c b/net/dsa-uclass.c
index 8a29188..bf762cd 100644
--- a/net/dsa-uclass.c
+++ b/net/dsa-uclass.c
@@ -216,7 +216,7 @@
 
 	label = ofnode_read_string(dev_ofnode(pdev), "label");
 	if (label)
-		strncpy(port_pdata->name, label, DSA_PORT_NAME_LENGTH);
+		strlcpy(port_pdata->name, label, DSA_PORT_NAME_LENGTH);
 
 	eth_pdata = dev_get_plat(pdev);
 	eth_pdata->priv_pdata = port_pdata;
@@ -421,7 +421,7 @@
 			struct dsa_port_pdata *port_pdata;
 
 			port_pdata = dev_get_parent_plat(pdev);
-			strncpy(port_pdata->name, name, DSA_PORT_NAME_LENGTH);
+			strlcpy(port_pdata->name, name, DSA_PORT_NAME_LENGTH);
 			pdev->name = port_pdata->name;
 		}