ACK: [SRU][J][PATCH 0/1] CVE-2025-38643

[Andrei Gherzan]

On 26/09/11 10:39AM, Cengiz Can via kernel-team wrote:
> https://ubuntu.com/security/CVE-2025-38643
> 
> [ Impact ]
> 
> In the Linux kernel, the following vulnerability has been resolved:
> 
> wifi: cfg80211: Add missing lock in cfg80211_check_and_end_cac()
> 
> Callers of wdev_chandef() must hold the wiphy mutex.
> 
> But the worker cfg80211_propagate_cac_done_wk() never takes the lock. Which
> triggers the warning below with the mesh_peer_connected_dfs test from hostapd
> and not (yet) released mac80211 code changes:
> 
> WARNING: CPU: 0 PID: 495 at net/wireless/chan.c:1552 wdev_chandef+0x60/0x165
> Modules linked in: CPU: 0 UID: 0 PID: 495 Comm: kworker/u4:2 Not tainted
> 6.14.0-rc5-wt-g03960e6f9d47 #33 13c287eeabfe1efea01c0bcc863723ab082e17cf
> Workqueue: cfg80211 cfg80211_propagate_cac_done_wk Stack: 00000000 00000001
> ffffff00 6093267c 00000000 6002ec30 6d577c50 60037608 00000000 67e8d108
> 6063717b 00000000 Call Trace: [<6002ec30>] ? _printk+0x0/0x98 [<6003c2b3>]
> show_stack+0x10e/0x11a [<6002ec30>] ? _printk+0x0/0x98 [<60037608>]
> dump_stack_lvl+0x71/0xb8 [<6063717b>] ? wdev_chandef+0x60/0x165 [<6003766d>]
> dump_stack+0x1e/0x20 [<6005d1b7>] __warn+0x101/0x20f [<6005d3a8>]
> warn_slowpath_fmt+0xe3/0x15d [<600b0c5c>] ? mark_lock.part.0+0x0/0x4ec
> [<60751191>] ? __this_cpu_preempt_check+0x0/0x16 [<600b11a2>] ?
> mark_held_locks+0x5a/0x6e [<6005d2c5>] ? warn_slowpath_fmt+0x0/0x15d
> [<60052e53>] ? unblock_signals+0x3a/0xe7 [<60052f2d>] ?
> um_set_signals+0x2d/0x43 [<60751191>] ? __this_cpu_preempt_check+0x0/0x16
> [<607508b2>] ? lock_is_held_type+0x207/0x21f [<6063717b>]
> wdev_chandef+0x60/0x165 [<605f89b4>] regulatory_propagate_dfs_state+0x247/0x43f
> [<60052f00>] ? um_set_signals+0x0/0x43 [<605e6bfd>]
> cfg80211_propagate_cac_done_wk+0x3a/0x4a [<6007e460>]
> process_scheduled_works+0x3bc/0x60e [<6007d0ec>] ? move_linked_works+0x4d/0x81
> [<6007d120>] ? assign_work+0x0/0xaa [<6007f81f>] worker_thread+0x220/0x2dc
> [<600786ef>] ? set_pf_worker+0x0/0x57 [<60087c96>] ? to_kthread+0x0/0x43
> [<6008ab3c>] kthread+0x2d3/0x2e2 [<6007f5ff>] ? worker_thread+0x0/0x2dc
> [<6006c05b>] ? calculate_sigpending+0x0/0x56 [<6003b37d>]
> new_thread_handler+0x4a/0x64 irq event stamp: 614611 hardirqs last enabled at
> (614621): [<00000000600bc96b>] __up_console_sem+0x82/0xaf hardirqs last
> disabled at (614630): [<00000000600bc92c>] __up_console_sem+0x43/0xaf softirqs
> last enabled at (614268): [<00000000606c55c6>]
> __ieee80211_wake_queue+0x933/0x985 softirqs last disabled at (614266):
> [<00000000606c52d6>] __ieee80211_wake_queue+0x643/0x985
> 
> [ Fix ]
> 
> jammy/linux: backported from 2c5dee15239f
> 
> The fix makes cfg80211_check_and_end_cac() acquire the wiphy mutex around
> the call path that reaches wdev_chandef() via
> regulatory_propagate_dfs_state(), satisfying the locking contract that
> callers of wdev_chandef() must hold the wiphy mutex.
> 
> This tree lacks the guard(wiphy) scope-based lock helper, so the backport
> replaces guard(wiphy)(&rdev->wiphy) with an explicit wiphy_lock() at
> function entry and wiphy_unlock() before the single return. It also omits
> the unused link_id, since this tree's loop uses wdev->chandef directly with
> no per-link iteration.
> 
> [ Test Plan ]
> 
> Build and boot tested.
> 
> [ Where Problems Could Occur ]
> 
> A regression would most likely surface in Wi-Fi setups that use DFS radar
> channels, such as access point, mesh, or IBSS configurations that run
> channel availability check (CAC) on the 5 GHz band across multiple radios
> sharing regulatory state. A mistake in the added locking could, in the
> worst case, cause a deadlock or lockdep splat in the cfg80211 CAC
> propagation path. Systems without Wi-Fi hardware, and Wi-Fi users who never
> operate on DFS channels, are not affected by this change.
> 
> [ Other Info ]
> 
> Kybele flow-v11-25-ga27c0fa6. Reference: 5705a2fe/v1

Acked-by: Andrei Gherzan <andrei.gherzan at canonical.com>

-- 
Andrei Gherzan
gpg: rsa4096/D4D94F67AD0E9640
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <https://lists.ubuntu.com/archives/kernel-team/attachments/20260915/ee6b1e17/attachment.sig>