In the Linux kernel, the following vulnerability has been resolved:
wifi: cfg80211: cancel sched scan results work on unregister
cfg80211_sched_scan_results() can queue rdev->sched_scan_res_wk from a
driver result notification while a scheduled scan request is present. The
work callback recovers the containing cfg80211_registered_device and then
locks the wiphy and walks the scheduled-scan request list.
wiphy_unregister() already makes the wiphy unreachable and drains rdev work
items before cfg80211_dev_free() can release the object, but it does not
drain sched_scan_res_wk. A queued or running result work item can therefore
cross the unregister/free boundary and access freed rdev state.
The buggy scenario involves two paths, with each column showing the order
within that path:
scheduled-scan result path: unregister/free path:
1. cfg80211_sched_scan_results() 1. interface teardown stops and
queues rdev->sched_scan_res_wk. removes the scheduled scan request.
2. cfg80211_wq starts the work 2. wiphy_unregister() drains other
item and recovers rdev. rdev work items.
3. The worker locks rdev->wiphy 3. cfg80211_dev_free() destroys and
and walks rdev state. frees rdev.
Cancel sched_scan_res_wk in wiphy_unregister() alongside the other rdev
work items. cancel_work_sync() removes a pending result notification and
waits for an already running callback, so cfg80211_dev_free() cannot free
rdev while this work item is still active.
Validation reproduced this kernel report:
BUG: KASAN: use-after-free in cfg80211_sched_scan_results_wk+0x4a6/0x530
Workqueue: cfg80211 cfg80211_sched_scan_results_wk [cfg80211]
Read of size 8
Call trace:
dump_stack_lvl+0x66/0xa0
print_report+0xce/0x630
cfg80211_sched_scan_results_wk+0x4a6/0x530
srso_alias_return_thunk+0x5/0xfbef5
__virt_addr_valid+0x224/0x430
kasan_report+0xac/0xe0
lockdep_hardirqs_on_prepare+0xea/0x1a0
process_one_work+0x8d0/0x18f0 (kernel/workqueue.c:3212)
lock_is_held_type+0x8f/0x100
worker_thread+0x5ad/0xfd0
__kthread_parkme+0xc6/0x200
kthread+0x31e/0x410
trace_hardirqs_on+0x1a/0x170
ret_from_fork+0x576/0x810
__switch_to+0x57e/0xe20
__switch_to_asm+0x33/0x70
ret_from_fork_asm+0x1a/0x30