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Tue, 16 Jun 2026 05:42:22 -0700 (PDT) Received: from [127.0.1.1] ([47.253.114.73]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2c42fbb50e5sm135274665ad.35.2026.06.16.05.42.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Jun 2026 05:42:22 -0700 (PDT) From: Wayen Yan To: netdev@vger.kernel.org Cc: lorenzo@kernel.org, horms@kernel.org, pabeni@redhat.com, kuba@kernel.org, edumazet@google.com, andrew+netdev@lunn.ch, angelogioacchino.delregno@collabora.com, matthias.bgg@gmail.com, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org Subject: [PATCH net v3] net: airoha: Fix skb->priority underflow in airoha_dev_select_queue() Date: Sun, 14 Jun 2026 07:30:54 +0800 Message-ID: <178161373805.2167512.2544164327472822616@gmail.com> Content-Type: text/plain; charset=utf-8 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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.). Fix by guarding the subtraction: when priority is 0, map to queue 0 (lowest priority), otherwise apply the original (priority - 1) % 8 mapping. Fixes: 2b288b81560b ("net: airoha: Introduce ndo_select_queue callback") Acked-by: Lorenzo Bianconi Reviewed-by: Joe Damato Signed-off-by: Wayen Yan --- drivers/net/ethernet/airoha/airoha_eth.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c index 31cdb11cd7..d476ef83c3 100644 --- a/drivers/net/ethernet/airoha/airoha_eth.c +++ b/drivers/net/ethernet/airoha/airoha_eth.c @@ -1933,7 +1933,7 @@ static u16 airoha_dev_select_queue(struct net_device *dev, struct sk_buff *skb, */ channel = netdev_uses_dsa(dev) ? 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 ? (skb->priority - 1) % AIROHA_NUM_QOS_QUEUES : 0; queue = channel * AIROHA_NUM_QOS_QUEUES + queue; return queue < dev->num_tx_queues ? queue : 0; -- 2.51.0