[PATCH 12/25] net: macb: ensure mdiodev->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/macb.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/macb.c b/drivers/net/macb.c
> index 57ea45e2dc7f..8151104acfc0 100644
> --- a/drivers/net/macb.c
> +++ b/drivers/net/macb.c
> @@ -1245,7 +1245,7 @@ int macb_eth_initialize(int id, void *regs, unsigned int phy_addr)
>         struct mii_dev *mdiodev = mdio_alloc();
>         if (!mdiodev)
>                 return -ENOMEM;
> -       strncpy(mdiodev->name, netdev->name, MDIO_NAME_LEN);
> +       strlcpy(mdiodev->name, netdev->name, MDIO_NAME_LEN);
>         mdiodev->read = macb_miiphy_read;
>         mdiodev->write = macb_miiphy_write;
>
> @@ -1403,7 +1403,7 @@ static int macb_eth_probe(struct udevice *dev)
>         macb->bus = mdio_alloc();
>         if (!macb->bus)
>                 return -ENOMEM;
> -       strncpy(macb->bus->name, dev->name, MDIO_NAME_LEN);
> +       strlcpy(macb->bus->name, dev->name, MDIO_NAME_LEN);
>         macb->bus->read = macb_miiphy_read;
>         macb->bus->write = macb_miiphy_write;
>
> --
> 2.25.1
>
Reviewed-by: Ramon Fried <rfried.dev at gmail.com>