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Mon, 07 Sep 2026 12:06:23 -0700 (PDT) From: =?UTF-8?q?=C3=96mer=20Mete=20Kaya?= To: netdev@vger.kernel.org Cc: oneukum@suse.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, =?UTF-8?q?=C3=96mer=20Mete=20Kaya?= , syzbot+04cd90bb99c6ef81a65d@syzkaller.appspotmail.com Subject: [PATCH] usbnet: fix smp_processor_id() use in preemptible context Date: Mon, 7 Sep 2026 22:05:25 +0300 Message-ID: <20260907190606.662033-1-omermetekaya0@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <6e0dbfed-cadd-4274-8165-886725413d0f@suse.com> References: <6e0dbfed-cadd-4274-8165-886725413d0f@suse.com> Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit usbnet_skb_return() and tx_complete() call this_cpu_ptr() before disabling preemption, which triggers a BUG when running with PREEMPT_FULL: BUG: using smp_processor_id() in preemptible code in tx_complete Fix by disabling preemption around the this_cpu_ptr() call and the per-CPU statistics update. Fixes: 43daa96b166c ("usbnet: Stop RX Q on MTU change") Reported-by: syzbot+04cd90bb99c6ef81a65d@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=04cd90bb99c6ef81a65d Signed-off-by: Ömer Mete Kaya --- v3: Use preempt_disable()/preempt_enable() instead of local_irq_save()/restore() as suggested by Oliver Neukum. drivers/net/usb/usbnet.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c index a19ecf718f36..f1e5bc8bf932 100644 --- a/drivers/net/usb/usbnet.c +++ b/drivers/net/usb/usbnet.c @@ -325,8 +325,7 @@ static void __usbnet_status_stop_force(struct usbnet *dev) */ void usbnet_skb_return(struct usbnet *dev, struct sk_buff *skb) { - struct pcpu_sw_netstats *stats64 = this_cpu_ptr(dev->net->tstats); - unsigned long flags; + struct pcpu_sw_netstats *stats64; int status; if (test_bit(EVENT_RX_PAUSED, &dev->flags)) { @@ -338,10 +337,13 @@ void usbnet_skb_return(struct usbnet *dev, struct sk_buff *skb) if (skb->protocol == 0) skb->protocol = eth_type_trans(skb, dev->net); - flags = u64_stats_update_begin_irqsave(&stats64->syncp); + preempt_disable(); + stats64 = this_cpu_ptr(dev->net->tstats); + u64_stats_update_begin(&stats64->syncp); u64_stats_inc(&stats64->rx_packets); u64_stats_add(&stats64->rx_bytes, skb->len); - u64_stats_update_end_irqrestore(&stats64->syncp, flags); + u64_stats_update_end(&stats64->syncp); + preempt_enable(); netif_dbg(dev, rx_status, dev->net, "< rx, len %zu, type 0x%x\n", skb->len + sizeof(struct ethhdr), skb->protocol); @@ -1298,13 +1300,15 @@ static void tx_complete(struct urb *urb) struct usbnet *dev = entry->dev; if (urb->status == 0) { - struct pcpu_sw_netstats *stats64 = this_cpu_ptr(dev->net->tstats); - unsigned long flags; + struct pcpu_sw_netstats *stats64; - flags = u64_stats_update_begin_irqsave(&stats64->syncp); + preempt_disable(); + stats64 = this_cpu_ptr(dev->net->tstats); + u64_stats_update_begin(&stats64->syncp); u64_stats_add(&stats64->tx_packets, entry->packets); u64_stats_add(&stats64->tx_bytes, entry->length); - u64_stats_update_end_irqrestore(&stats64->syncp, flags); + u64_stats_update_end(&stats64->syncp); + preempt_enable(); } else { dev->net->stats.tx_errors++; -- 2.55.0