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

[Lorenzo Bianconi <lorenzo@kernel.org>]

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> 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.

ack, I will fix it in v2.

Regards,
Lorenzo

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

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