wifi: cfg80211: convert pmsr_free_wk to wiphy_work to fix deadlock

Overview

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

wifi: cfg80211: convert pmsr_free_wk to wiphy_work to fix deadlock

When a netlink socket that owns a PMSR session is closed, cfg80211_release_pmsr() clears the request's nl_portid and queues pmsr_free_wk to call cfg80211_pmsr_process_abort() asynchronously.

If the interface tears down concurrently, cfg80211_pmsr_wdev_down() is called under wiphy_lock and calls cancel_work_sync(&pmsr_free_wk) to wait for any running work. The work function acquires wiphy_lock via guard(wiphy) before calling process_abort.

This is a deadlock: wdev_down holds wiphy_lock and blocks inside cancel_work_sync(); pmsr_free_wk blocks trying to acquire that same wiphy_lock. Neither thread can proceed.

The same deadlock is reachable from cfg80211_leave_locked(), which calls cfg80211_pmsr_wdev_down() for all interface types under wiphy_lock.

Fix this by converting pmsr_free_wk from a plain work_struct to a wiphy_work. The wiphy_work dispatcher holds wiphy_lock when running work items, so the explicit guard(wiphy) in the work function is no longer needed. wiphy_work_cancel() can be called safely while holding wiphy_lock - since wiphy_lock prevents the work from running concurrently, wiphy_work_cancel() never blocks, eliminating the deadlock.

Remove the cancel_work_sync() for pmsr_free_wk from the NETDEV_GOING_DOWN handler. cfg80211_leave(), called unconditionally just before it, already cancels any pending work under wiphy_lock via wiphy_work_cancel() inside cfg80211_pmsr_wdev_down().

Affected

• Linux >= 37e776e2e0a523731e2470dce6d563f0e8632a40 < 30c67926d41c456809857976cd3cd71b2290e0c1
• Linux >= d32c07ef1880fe20cf4ab223dbfedc9c0b2816aa < 21512b5f7a74fd18c996c22e6854efe57d570816
• Linux >= a1b7a843f12a0c3e9d3a2ca607ce451916ef42cf < 133684982dd0c24359fcc641d19d89cc17d6e5ef
• Linux >= 6dccbc9f3e1d38565dff7730d2b7d1e8b16c9b09 < 0a77d9fb4d5c0e01306cd406ffdee8f1fe955c0e
• Linux >= 6dccbc9f3e1d38565dff7730d2b7d1e8b16c9b09 < 2b0eab425e1f658d8fe1df7590e3b9af5959505e
• Linux 28d3551f8d8cb3aec7497894d94150fe84d20e5e
• Linux 72b7ea786b8e570ae11149e9089859a4a8634a13
• Linux >= 6.6.130 < 6.6.160
• Linux >= 6.12.78 < 6.12.101
• Linux >= 6.18.20 < 6.18.42
• Linux >= 6.1.167 < 6.2
• Linux >= 6.19.10 < 6.20
• Linux 7.0

Remediation

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