CVE-2026-63821

In the Linux kernel, the following vulnerability has been resolved:

wifi: rtw88: usb: fix memory leaks on USB write failures

When rtw_usb_write_port() fails to submit a USB Request Block (URB)
(e.g., due to device disconnect or ENOMEM), the completion callback is
never executed.

Currently, the driver ignores the return value of rtw_usb_write_port()
in rtw_usb_write_data() and rtw_usb_tx_agg_skb(). Because these
functions rely on the completion callback to free the socket buffers
(skbs) and the transaction control block (txcb), a submission failure
results in:
1. A memory leak of the allocated skb in rtw_usb_write_data().
2. A memory leak of the txcb structure and all aggregated skbs in
rtw_usb_tx_agg_skb().

Fix this by checking the return value of rtw_usb_write_port(). If it
fails, explicitly free the skb in rtw_usb_write_data(), and properly
purge the tx_ack_queue and free the txcb in rtw_usb_tx_agg_skb().

The issue was discovered in practice during device disconnect/reconnect
scenarios and memory pressure conditions. Tested by verifying normal TX
operation continues after the fix without regressions.