wifi: mac80211: shut down RX BA session timer on teardown

Overview

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

wifi: mac80211: shut down RX BA session timer on teardown

Tearing down an RX BA session can leave the session timer queued on a freed tid_rx. Later timer-wheel processing and the timer callback itself then run against freed memory.

An RX BAR handler can dereference tid_rx under RCU before teardown unpublishes it and stay in its read-side critical section while teardown deletes the session timer. The stale handler can then rearm the timer after timer_delete_sync() returns and before the RCU callback frees tid_rx.

Use timer_shutdown_sync() so rearm attempts become ineffective once teardown starts. Keep reorder_timer unchanged: teardown marks the session removed under reorder_lock and its release path checks that state before rearming. session_timer has no equivalent guard because ieee80211_rx_h_ctrl() rearms it before taking reorder_lock.

Affected

• Linux >= a87f736d942c86255e3088c606f0e3eab6bbf784 < 7bb2a5bd4f07192fca35644fab7d49a17bfbc861
• Linux >= a87f736d942c86255e3088c606f0e3eab6bbf784 < 481f9230284c27052b59c587069f232c5d84779e
• Linux >= a87f736d942c86255e3088c606f0e3eab6bbf784 < 09b7d5e4f88504e62ddf4ff31ebeebb3b87578ba
• Linux >= a87f736d942c86255e3088c606f0e3eab6bbf784 < e588e83e5c7a0f6d7a77dbbb58927c8c8cfd598e
• Linux 2.6.36

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.