[PATCH 23/25] net: dsa: ensure port names are NULL-terminated after DSA_PORT_NAME_LENGTH 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 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 at nxp.com>
> ---
>  net/dsa-uclass.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/dsa-uclass.c b/net/dsa-uclass.c
> index 9b8ae1e82b92..8db0de686e2a 100644
> --- a/net/dsa-uclass.c
> +++ b/net/dsa-uclass.c
> @@ -221,7 +221,7 @@ static int dsa_port_of_to_pdata(struct udevice *pdev)
>
>         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;
> @@ -433,7 +433,7 @@ static int dsa_post_bind(struct udevice *dev)
>                         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;
>                 }
>
> --
> 2.25.1
>
Reviewed-by: Ramon Fried <rfried.dev at gmail.com>