syzbot reported WARNING in rtl8150_start_xmit/usb_submit_urb. This is the sequence of events that leads to the Warning: CPU0 (in rtl8150_start_xmit) CPU1 (in rtl8150_start_xmit) CPU2 (in rtl8150_set_multicast) netif_stop_queue(); netif_stop_queue(); usb_submit_urb(); netif_wake_queue(); <-- Wakes up TX queue before it's ready netif_stop_queue(); usb_submit_urb(); <-- Warning freeing urb rtl8150_set_multicast is rtl8150's implementation of ndo_set_rx_mode and should not be calling netif_stop_queue and notif_start_queue as these handle TX queue synchronization. The net core function dev_set_rx_mode handles the synchronization for rtl8150_set_multicast making it safe to remove these locks. Reported-and-tested-by: syzbot+78cae3f37c62ad092caa@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=78cae3f37c62ad092caa Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: I Viswanath --- v2: - Add explanation why netif_stop_queue/netif_wake_queue can be safely removed - Add the net prefix to the patch, designating it to the net tree Relevant logs: [ 65.779651][ T5648] About to enter stop queue ffff88805061e000, eth4 [ 65.779664][ T5648] After stop queue ffff88805061e000, eth4 [ 65.780296][ T5648] net eth4: eth name:eth4 SUBMIT: tx_urb=ffff888023219000, status=0, transfer_buffer_length=60, dev=ffff88805061ed80, netdev=ffff88805061e000, skb=ffff88804f907b80 [ 65.790962][ T760] About to enter stop queue ffff88805061e000, eth4 [ 65.790978][ T760] After stop queue ffff88805061e000, eth4 [ 65.791874][ T760] net eth4: We are inside Multicast dev:ffff88805061ed80, netdev:ffff88805061e000 [ 65.793259][ T760] About to enter netif_wake_queue ffff88805061e000, eth4 [ 65.793264][ T760] After netif_wake_queue ffff88805061e000, eth4 [ 65.822319][ T5829] About to enter stop queue ffff88805061e000, eth4 [ 65.823135][ T5829] After stop queue ffff88805061e000, eth4 [ 65.823739][ T5829] net eth4: eth name:eth4 SUBMIT: tx_urb=ffff888023219000, status=-115, transfer_buffer_length=90, dev=ffff88805061ed80, netdev=ffff88805061e000, skb=ffff88804b5363c0 drivers/net/usb/rtl8150.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/net/usb/rtl8150.c b/drivers/net/usb/rtl8150.c index ddff6f19ff98..92add3daadbb 100644 --- a/drivers/net/usb/rtl8150.c +++ b/drivers/net/usb/rtl8150.c @@ -664,7 +664,6 @@ static void rtl8150_set_multicast(struct net_device *netdev) rtl8150_t *dev = netdev_priv(netdev); u16 rx_creg = 0x9e; - netif_stop_queue(netdev); if (netdev->flags & IFF_PROMISC) { rx_creg |= 0x0001; dev_info(&netdev->dev, "%s: promiscuous mode\n", netdev->name); @@ -678,7 +677,6 @@ static void rtl8150_set_multicast(struct net_device *netdev) rx_creg &= 0x00fc; } async_set_registers(dev, RCR, sizeof(rx_creg), rx_creg); - netif_wake_queue(netdev); } static netdev_tx_t rtl8150_start_xmit(struct sk_buff *skb, -- 2.47.3