[PATCH 14/25] net: dsa: felix: ensure mii_bus->name is NULL terminated after MDIO_NAME_LEN truncation

[Ramon Fried]

On Mon, Sep 27, 2021 at 2:22 PM Vladimir Oltean <vladimir.oltean at nxp.com> wrote:
>
> 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 at nxp.com>
> ---
>  drivers/net/mscc_eswitch/felix_switch.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/mscc_eswitch/felix_switch.c b/drivers/net/mscc_eswitch/felix_switch.c
> index 6aa79784460d..4c2e57755967 100644
> --- a/drivers/net/mscc_eswitch/felix_switch.c
> +++ b/drivers/net/mscc_eswitch/felix_switch.c
> @@ -258,7 +258,7 @@ static void felix_init(struct udevice *dev)
>         priv->imdio.read = felix_mdio_read;
>         priv->imdio.write = felix_mdio_write;
>         priv->imdio.priv = priv->imdio_base + FELIX_PM_IMDIO_BASE;
> -       strncpy(priv->imdio.name, dev->name, MDIO_NAME_LEN);
> +       strlcpy(priv->imdio.name, dev->name, MDIO_NAME_LEN);
>
>         /* set up CPU port */
>         out_le32(base + FELIX_QSYS_SYSTEM_EXT_CPU_CFG,
> @@ -303,7 +303,7 @@ static int felix_probe(struct udevice *dev)
>                 mii_bus->read = felix_mdio_read;
>                 mii_bus->write = felix_mdio_write;
>                 mii_bus->priv = priv->imdio_base + FELIX_PM_IMDIO_BASE;
> -               strncpy(mii_bus->name, dev->name, MDIO_NAME_LEN);
> +               strlcpy(mii_bus->name, dev->name, MDIO_NAME_LEN);
>                 mdio_register(mii_bus);
>         }
>
> --
> 2.25.1
>
Reviewed-by: Ramon Fried <rfried.dev at gmail.com>