CVE-2022-49326: rtl818x: Prevent using not initialized queues

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

rtl818x: Prevent using not initialized queues

Using not existing queues can panic the kernel with rtl8180/rtl8185 cards. Ignore the skb priority for those cards, they only have one tx queue. Pierre Asselin (pa@panix.com) reported the kernel crash in the Gentoo forum:

https://forums.gentoo.org/viewtopic-t-1147832-postdays-0-postorder-asc-start-25.html

He also confirmed that this patch fixes the issue. In summary this happened:

After updating wpasupplicant from 2.9 to 2.10 the kernel crashed with a "divide error: 0000" when connecting to an AP. Control port tx now tries to use IEEE80211ACVO for the priority, which wpasupplicants starts to use in 2.10.

Since only the rtl8187se part of the driver supports QoS, the priority of the skb is set to IEEE80211ACBE (2) by mac80211 for rtl8180/rtl8185 cards.

rtl8180 is then unconditionally reading out the priority and finally crashes on drivers/net/wireless/realtek/rtl818x/rtl8180/dev.c line 544 without this patch: idx = (ring->idx + skbqueuelen(&ring->queue)) % ring->entries

"ring->entries" is zero for rtl8180/rtl8185 cards, txring[2] never got initialized.