Re: [PATCH net v2 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 Fri, Jun 19, 2026 at 01:37:14PM +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>
> 
> Thanks for the update since v1.
> 
> Reviewed-by: Simon Horman <horms@kernel.org>

Hi Simon,

thx for the review.

> 
> FTR, there is an AI-generated review of this patch on sashiko.dev.
> I do not think that should impede the progress of this patch but
> you may want to consider it in the context of follow-up.

Even if it is not introduced by this patch, I do not think what is reported
by Sashiko is a real issue since airoha_eth driver implements
ndo_select_queue() callback and the selected queue is always in the range
[0, AIROHA_NUM_TX_RING[. HTB queues (in the range
[AIROHA_NUM_TX_RING, AIROHA_NUM_TX_RING + AIROHA_NUM_QOS_CHANNELS[) are just 
'offloaded' and never used in the TC sw path. Agree?

Regards,
Lorenzo

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