Re: [PATCH net] usbnet: fix crash due to missing BQL accounting after resume
From: Eric Dumazet <edumazet@google.com>
Date: 2026-01-13 08:33:35
Also in:
linux-usb, lkml
On Tue, Jan 13, 2026 at 8:51 AM Simon Schippers [off-list ref] wrote:
In commit 7ff14c52049e ("usbnet: Add support for Byte Queue Limits
(BQL)"), it was missed that usbnet_resume() may enqueue SKBs using
__skb_queue_tail() without reporting them to BQL. As a result, the next
call to netdev_completed_queue() triggers a BUG_ON() in dql_completed(),
since the SKBs queued during resume were never accounted for.
This patch fixes the issue by adding a corresponding netdev_sent_queue()
call in usbnet_resume() when SKBs are queued after suspend. Because
dev->txq.lock is held at this point, no concurrent calls to
netdev_sent_queue() from usbnet_start_xmit() can occur.
The crash can be reproduced by generating network traffic
(e.g. iperf3 -c ... -t 0), suspending the system, and then waking it up
(e.g. rtcwake -m mem -s 5).
When testing USB2 Android tethering (cdc_ncm), the system crashed within
three suspend/resume cycles without this patch. With the patch applied,
no crashes were observed after 90 cycles. Testing with an AX88179 USB
Ethernet adapter also showed no crashes.
Reported-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Tested-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Tested-by: Simon Schippers <redacted>
Signed-off-by: Simon Schippers <redacted>
---
We request/need Fixes: tag for net patches, in the footer.
And we prefer it to be the first tag.
Fixes: 7ff14c52049e ("usbnet: Add support for Byte Queue Limits (BQL)")
...
Reviewed-by: Eric Dumazet <edumazet@google.com>
Thanks !
quoted hunk ↗ jump to hunk
drivers/net/usb/usbnet.c | 1 + 1 file changed, 1 insertion(+)diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c index 36742e64cff7..35789ff4dd55 100644 --- a/drivers/net/usb/usbnet.c +++ b/drivers/net/usb/usbnet.c@@ -1984,6 +1984,7 @@ int usbnet_resume(struct usb_interface *intf) } else { netif_trans_update(dev->net); __skb_queue_tail(&dev->txq, skb); + netdev_sent_queue(dev->net, skb->len); } } --2.43.0