In the Linux kernel, the following vulnerability has been resolved:
wifi: mac80211: free AP_VLAN bc_buf SKBs outside IRQ lock
ieee80211_do_stop() removes AP_VLAN packets from the parent AP ps->bc_buf while holding ps->bc_buf.lock with IRQs disabled. It then calls ieee80211_free_txskb() before dropping the lock.
ieee80211_free_txskb() is not just a passive SKB release. For SKBs with TX status state it can report a dropped frame through cfg80211/nl80211, and that path can reach netlink tap transmit. This is the same reason the pending queue cleanup in ieee80211_do_stop() already unlinks SKBs under the queue lock and frees them after IRQ state is restored.
The buggy scenario involves two paths, with each column showing the order within that path:
AP_VLAN management TX: AP_VLAN stop:
- attach ACK-status state 1. clear the running state
- queue a multicast SKB on 2. take ps->bc_buf.lock with IRQs parent ps->bc_buf disabled 3. unlink the AP_VLAN SKB 4. call ieee80211_free_txskb()
Unlink matching AP_VLAN SKBs from ps->bc_buf under the existing lock, but move them to a local free queue. Drop the lock and restore IRQ state before calling ieee80211_free_txskb().
WARNING: kernel/softirq.c:430 at __local_bh_enable_ip
References
- https://git.kernel.org/stable/c/4b8abf43bf34791c99d99dc3be13f897adefc461
- https://git.kernel.org/stable/c/962f755a47d7ec3bbf6c709697d7f4c5f798441d
- https://git.kernel.org/stable/c/a424985c3ef2a87ce6057a853e18d0c441a86be8
- https://git.kernel.org/stable/c/be9dfcb0654c1f6c0fce7ba2a909683bb6f1e0ef
- https://git.kernel.org/stable/c/f3858d5b1432098c1936e03d6e03dd0e33facf60