Re: [PATCH net 2/2] net: airoha: fix netif_set_real_num_tx_queues for sparse QoS channels

[Simon Horman <horms@kernel.org>]

On Thu, Jun 18, 2026 at 08:00:30AM +0200, Lorenzo Bianconi wrote:
> airoha_tc_htb_alloc_leaf_queue() assigns queue IDs based on the channel
> index (opt->qid = AIROHA_NUM_TX_RING + channel), but updates
> real_num_tx_queues with a simple increment (num_tx_queues + 1). When QoS
> channels are allocated sparsely (e.g., channels 0 and 3 without 1 and
> 2), the returned qid can exceed real_num_tx_queues, causing out-of-bounds
> accesses in the networking stack.
> For example, allocating channel 0 then channel 3 results in
> real_num_tx_queues = 34 but qid = 35, which is out of range [0, 34).
> Fix this by computing real_num_tx_queues based on the highest active
> channel index rather than using a simple counter, in both the allocation
> and deletion paths.
> 
> Fixes: ef1ca9271313b ("net: airoha: Add sched HTB offload support")
> Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> ---
>  drivers/net/ethernet/airoha/airoha_eth.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c

...

> @@ -2806,7 +2806,10 @@ static int airoha_tc_htb_alloc_leaf_queue(struct net_device *netdev,
>  	if (err)
>  		goto error;
>  
> -	err = netif_set_real_num_tx_queues(netdev, num_tx_queues + 1);
> +	if (num_tx_queues <= netdev->real_num_tx_queues)
> +		goto set_qos_sq_bmap;
> +
> +	err = netif_set_real_num_tx_queues(netdev, num_tx_queues);
>  	if (err) {
>  		airoha_qdma_set_tx_rate_limit(netdev, channel, 0,
>  					      opt->quantum);
> @@ -2815,6 +2818,7 @@ static int airoha_tc_htb_alloc_leaf_queue(struct net_device *netdev,
>  		goto error;
>  	}
>  
> +set_qos_sq_bmap:

I would prefer if this could be achieved without a goto.

>  	set_bit(channel, dev->qos_sq_bmap);
>  	opt->qid = AIROHA_NUM_TX_RING + channel;
>  

...