Re: [PATCH net 08/12] net: systemport: Fix out-of-bounds array accesses in DSA queue mapping

[Nicolai Buchwitz <nb@tipi-net.de>]

Hi Florian

On 22.9.2026 01:13, Florian Fainelli wrote:
> The priv->ring_map array has a fixed size of (DSA_MAX_PORTS * 8). In
> bcm_sysport_select_queue(), bcm_sysport_map_queues(), and
> bcm_sysport_unmap_queues(), indices calculated as
> (qp + port * num_tx_queues) were accessed without checking against
> ARRAY_SIZE(priv->ring_map). If unusual port or queue configurations are
> encountered, this could lead to out-of-bounds array accesses.
> 
> Additionally, on SYSTEMPORT Lite, netif_set_real_num_tx_queues() was
> called with slave_dev->num_tx_queues / 2, which could evaluate to 0 if
> slave_dev->num_tx_queues is 1, causing netif_set_real_num_tx_queues() 
> to
> fail with -EINVAL.
> 
> Fix these by clamping the real number of queues to at least 1 and 
> adding
> bounds checks on priv->ring_map.
> 
> Fixes: d156576362c0 ("net: systemport: Establish lower/upper queue 
> mapping")
> Assisted-by: LLM
> Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
> ---
>  drivers/net/ethernet/broadcom/bcmsysport.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/broadcom/bcmsysport.c 
> b/drivers/net/ethernet/broadcom/bcmsysport.c
> index 95cead1df160..130545cce045 100644
> --- a/drivers/net/ethernet/broadcom/bcmsysport.c
> +++ b/drivers/net/ethernet/broadcom/bcmsysport.c

> [...]

> @@ -2352,7 +2356,8 @@ static int bcm_sysport_map_queues(struct 
> net_device *dev,
>  		ring->switch_queue = qp;
>  		ring->switch_port = port;
>  		ring->inspect = true;
> -		priv->ring_map[qp + port * num_tx_queues] = ring;
> +		if (qp + port * num_tx_queues < ARRAY_SIZE(priv->ring_map))
> +			priv->ring_map[qp + port * num_tx_queues] = ring;

Out of range rings would still have inspect = true but no ring_map
entry, so select_queue() can never pick them.

Bail out before marking the ring?

> [...]

Thanks,
Nicolai