net: smc911x: ensure mdiodev->name is NULL terminated after MDIO_NAME_LEN 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 MDIO_NAME_LEN - 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/drivers/net/smc911x.c b/drivers/net/smc911x.c
index 8f420261fa8d9fdff694c99ab8488ec64006b214..5d9a73f23d750c13b1fddf56cd476fb3f43c97ea 100644 (file)
--- a/drivers/net/smc911x.c
+++ b/drivers/net/smc911x.c
@@ -425,7 +425,7 @@ static int smc911x_initialize_mii(struct smc911x_priv *priv)
        if (!mdiodev)
                return -ENOMEM;
 
-       strncpy(mdiodev->name, priv->dev.name, MDIO_NAME_LEN);
+       strlcpy(mdiodev->name, priv->dev.name, MDIO_NAME_LEN);
        mdiodev->read = smc911x_miiphy_read;
        mdiodev->write = smc911x_miiphy_write;