From: Wayen Yan Date: Sat, 20 Jun 2026 08:17:44 +0000 (+0800) Subject: net: airoha: Fix skb->priority underflow in airoha_dev_select_queue() X-Git-Tag: v7.2-rc1~29^2~71 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=86e51aa24686cc95bb35613059e8b94b9b81e3f0;p=thirdparty%2Flinux.git net: airoha: Fix skb->priority underflow in airoha_dev_select_queue() In airoha_dev_select_queue(), the expression: queue = (skb->priority - 1) % AIROHA_NUM_QOS_QUEUES; implicitly converts to unsigned arithmetic: when skb->priority is 0 (the default for unclassified traffic), (0u - 1u) wraps to UINT_MAX, and UINT_MAX % 8 = 7, routing default best-effort packets to the highest-priority QoS queue. This causes QoS inversion where the majority of traffic on a PON gateway starves actual high-priority flows (VoIP, gaming, etc.). The "- 1" offset was a leftover from the ETS offload implementation that has since been removed. The correct mapping is a direct modulo: queue = skb->priority % AIROHA_NUM_QOS_QUEUES; This maps priority 0 → queue 0 (lowest), priority 7 → queue 7 (highest), with higher priorities wrapping around. This is the standard Linux sk_prio → HW queue mapping used by other drivers. Fixes: 2b288b81560b ("net: airoha: Introduce ndo_select_queue callback") Link: https://lore.kernel.org/netdev/178185573207.2378135.3729126358670287878@gmail.com/ Acked-by: Lorenzo Bianconi Reviewed-by: Joe Damato Signed-off-by: Wayen Yan Link: https://patch.msgid.link/178194366700.2485734.5368768965976693502@gmail.com Signed-off-by: Jakub Kicinski --- diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c index 64dde6464f3fb..3370c3df7c107 100644 --- a/drivers/net/ethernet/airoha/airoha_eth.c +++ b/drivers/net/ethernet/airoha/airoha_eth.c @@ -2110,7 +2110,7 @@ static u16 airoha_dev_select_queue(struct net_device *netdev, */ channel = netdev_uses_dsa(netdev) ? skb_get_queue_mapping(skb) : port->id; channel = channel % AIROHA_NUM_QOS_CHANNELS; - queue = (skb->priority - 1) % AIROHA_NUM_QOS_QUEUES; /* QoS queue */ + queue = skb->priority % AIROHA_NUM_QOS_QUEUES; queue = channel * AIROHA_NUM_QOS_QUEUES + queue; return queue < netdev->num_tx_queues ? queue : 0;