Re: [PATCH 01/25] arch: powerpc: mpc85xx: ensure mdiodev->name is NULL terminated after MDIO_NAME_LEN truncation

[Ramon Fried <rfried.dev@gmail.com>]

On Mon, Sep 27, 2021 at 2:22 PM Vladimir Oltean <vladimir.oltean@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@nxp.com>
> ---
>  arch/powerpc/cpu/mpc85xx/ether_fcc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/cpu/mpc85xx/ether_fcc.c b/arch/powerpc/cpu/mpc85xx/ether_fcc.c
> index 3c4eb1a7eba9..1f6f55707321 100644
> --- a/arch/powerpc/cpu/mpc85xx/ether_fcc.c
> +++ b/arch/powerpc/cpu/mpc85xx/ether_fcc.c
> @@ -444,7 +444,7 @@ int fec_initialize(struct bd_info *bis)
>                 struct mii_dev *mdiodev = mdio_alloc();
>                 if (!mdiodev)
>                         return -ENOMEM;
> -               strncpy(mdiodev->name, dev->name, MDIO_NAME_LEN);
> +               strlcpy(mdiodev->name, dev->name, MDIO_NAME_LEN);
>                 mdiodev->read = bb_miiphy_read;
>                 mdiodev->write = bb_miiphy_write;
>
> --
> 2.25.1
>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>