wifi: mac80211: refuse to make a monitor active when it has no queue

In the Linux kernel, the following vulnerability has been resolved: wifi: mac80211: refuse to make a monitor active when it has no queue A monitor interface only gets a TXQ if it's created active, and one can't be added later. Setting the flag on a down interface is still allowed, so the driver is handed a monitor with no queue. ath9k dereferences it: BUG: kernel NULL pointer dereference, address: 0000000000000066 RIP: 0010:ath_tx_node_init+0x49/0x170 [ath9k] ath9k_add_interface+0x10c/0x140 [ath9k] drv_add_interface+0x54/0x250 [mac80211] ieee80211_do_open+0x32f/0x800 [mac80211] Reached with CAP_NET_ADMIN by "iw dev X set monitor active" followed by "ip link set X up". RTNL is held, so netlink operations block behind it. Refuse the flag when there is no queue to give.

Source published

6 Oct 2026 08:44:25 UTC

Source modified

19 Oct 2026 09:15:13 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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