Re: [PATCH] net: dsa: felix: check felix_cpu_port_for_conduit() for failure

[Andrew Lunn]

On Wed, Mar 26, 2025 at 09:12:45PM +0500, Vitaliy Shevtsov wrote:
> felix_cpu_port_for_conduit() can return a negative value in case of failure
> and then it will be used as a port index causing buffer underflow. This can
> happen if a bonding interface in 802.1Q mode has no ports. This is unlikely
> to happen because the underlying driver handles IFF_TEAM, IFF_MASTER,
> IFF_BONDING bits and ports populating correctly, it is still better to
> check this for correctness if somehow it fails.
> 
> Check if cpu_port is non-negative before using it as an index.
> Errors from change_conduit() are already handled and no additional changes
> are required.
> 
> Found by Linux Verification Center (linuxtesting.org) with Svace.
> 
> Signed-off-by: Vitaliy Shevtsov <v.shevtsov@xxxxxxxxxxxxxxxxx>
> ---
>  drivers/net/dsa/ocelot/felix.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/dsa/ocelot/felix.c b/drivers/net/dsa/ocelot/felix.c
> index 0a4e682a55ef..1495f8e21f90 100644
> --- a/drivers/net/dsa/ocelot/felix.c
> +++ b/drivers/net/dsa/ocelot/felix.c
> @@ -523,6 +523,7 @@ static int felix_tag_npi_change_conduit(struct dsa_switch *ds, int port,
>  {
>  	struct dsa_port *dp = dsa_to_port(ds, port), *other_dp;
>  	struct ocelot *ocelot = ds->priv;
> +	int cpu;
>  
>  	if (netif_is_lag_master(conduit)) {
>  		NL_SET_ERR_MSG_MOD(extack,
> @@ -546,7 +547,12 @@ static int felix_tag_npi_change_conduit(struct dsa_switch *ds, int port,
>  	}
>  
>  	felix_npi_port_deinit(ocelot, ocelot->npi);
> -	felix_npi_port_init(ocelot, felix_cpu_port_for_conduit(ds, conduit));
> +	cpu = felix_cpu_port_for_conduit(ds, conduit);
> +	if (cpu < 0) {
> +		dev_err(ds->dev, "Cpu port for conduit not found\n");
> +		return -EINVAL;
> +	}

If i'm reading the code correctly you mean ocelot_bond_get_id()
returns -ENOENT?

If so, you should return the ENOENT, not replace it by EINVAL.

	Andrew