CVE-2022-50881 in Linux
Summary
by MITRE • 12/30/2025
In the Linux kernel, the following vulnerability has been resolved:
wifi: ath9k: Fix use-after-free in ath9k_hif_usb_disconnect()
This patch fixes a use-after-free in ath9k that occurs in ath9k_hif_usb_disconnect() when ath9k_destroy_wmi() is trying to access 'drv_priv' that has already been freed by ieee80211_free_hw(), called by ath9k_htc_hw_deinit(). The patch moves ath9k_destroy_wmi() before ieee80211_free_hw(). Note that urbs from the driver should be killed before freeing 'wmi' with ath9k_destroy_wmi() as their callbacks will access 'wmi'.
Found by a modified version of syzkaller.
================================================================== BUG: KASAN: use-after-free in ath9k_destroy_wmi+0x38/0x40 Read of size 8 at addr ffff8881069132a0 by task kworker/0:1/7
CPU: 0 PID: 7 Comm: kworker/0:1 Tainted: G O 5.14.0+ #131 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014 Workqueue: usb_hub_wq hub_event Call Trace: dump_stack_lvl+0x8e/0xd1 print_address_description.constprop.0.cold+0x93/0x334 ? ath9k_destroy_wmi+0x38/0x40 ? ath9k_destroy_wmi+0x38/0x40 kasan_report.cold+0x83/0xdf ? ath9k_destroy_wmi+0x38/0x40 ath9k_destroy_wmi+0x38/0x40 ath9k_hif_usb_disconnect+0x329/0x3f0 ? ath9k_hif_usb_suspend+0x120/0x120 ? usb_disable_interface+0xfc/0x180 usb_unbind_interface+0x19b/0x7e0 ? usb_autoresume_device+0x50/0x50 device_release_driver_internal+0x44d/0x520 bus_remove_device+0x2e5/0x5a0 device_del+0x5b2/0xe30 ? __device_link_del+0x370/0x370 ? usb_remove_ep_devs+0x43/0x80 ? remove_intf_ep_devs+0x112/0x1a0 usb_disable_device+0x1e3/0x5a0 usb_disconnect+0x267/0x870 hub_event+0x168d/0x3950 ? rcu_read_lock_sched_held+0xa1/0xd0 ? hub_port_debounce+0x2e0/0x2e0 ? check_irq_usage+0x860/0xf20 ? drain_workqueue+0x281/0x360 ? lock_release+0x640/0x640 ? rcu_read_lock_sched_held+0xa1/0xd0 ? rcu_read_lock_bh_held+0xb0/0xb0 ? lockdep_hardirqs_on_prepare+0x273/0x3e0 process_one_work+0x92b/0x1460 ? pwq_dec_nr_in_flight+0x330/0x330 ? rwlock_bug.part.0+0x90/0x90 worker_thread+0x95/0xe00 ? __kthread_parkme+0x115/0x1e0 ? process_one_work+0x1460/0x1460 kthread+0x3a1/0x480 ? set_kthread_struct+0x120/0x120 ret_from_fork+0x1f/0x30
The buggy address belongs to the page: page:ffffea00041a44c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x106913 flags: 0x200000000000000(node=0|zone=2) raw: 0200000000000000 0000000000000000 dead000000000122 0000000000000000 raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as freed page last allocated via order 3, migratetype Unmovable, gfp_mask 0x40dc0(GFP_KERNEL|__GFP_COMP|__GFP_ZERO), pid 7, ts 38347963444, free_ts 41399957635 prep_new_page+0x1aa/0x240 get_page_from_freelist+0x159a/0x27c0 __alloc_pages+0x2da/0x6a0 alloc_pages+0xec/0x1e0 kmalloc_order+0x39/0xf0 kmalloc_order_trace+0x19/0x120 __kmalloc+0x308/0x390 wiphy_new_nm+0x6f5/0x1dd0 ieee80211_alloc_hw_nm+0x36d/0x2230 ath9k_htc_probe_device+0x9d/0x1e10 ath9k_htc_hw_init+0x34/0x50 ath9k_hif_usb_firmware_cb+0x25f/0x4e0 request_firmware_work_func+0x131/0x240 process_one_work+0x92b/0x1460 worker_thread+0x95/0xe00 kthread+0x3a1/0x480 page last free stack trace: free_pcp_prepare+0x3d3/0x7f0 free_unref_page+0x1e/0x3d0 device_release+0xa4/0x240 kobject_put+0x186/0x4c0 put_device+0x20/0x30 ath9k_htc_disconnect_device+0x1cf/0x2c0 ath9k_htc_hw_deinit+0x26/0x30 ath9k_hif_usb_disconnect+0x2d9/0x3f0 usb_unbind_interface+0x19b/0x7e0 device_release_driver_internal+0x44d/0x520 bus_remove_device+0x2e5/0x5a0 device_del+0x5b2/0xe30 usb_disable_device+0x1e3/0x5a0 usb_disconnect+0x267/0x870 hub_event+0x168d/0x3950 process_one_work+0x92b/0x1460
Memory state around the buggy address: ffff888106913180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff888106913200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff >ffff888 ---truncated---
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Analysis
by VulDB Data Team • 04/26/2026
The vulnerability CVE-2022-50881 addresses a critical use-after-free condition within the Linux kernel's ath9k wireless driver, specifically in the ath9k_hif_usb_disconnect function. This flaw arises from an improper sequence of operations during USB device disconnection, where memory that has already been freed is accessed by subsequent code paths. The issue occurs when ath9k_destroy_wmi() attempts to access the drv_priv structure, which has already been released by ieee80211_free_hw(), invoked during ath9k_htc_hw_deinit(). The improper ordering leads to a memory access violation that can result in system instability or potential exploitation. This vulnerability was identified through a modified version of the syzkaller fuzzer, highlighting its significance in real-world kernel testing environments.
The technical root cause involves a classic race condition and memory management error where device cleanup operations are not properly sequenced. During USB disconnection, the driver performs a series of cleanup operations in the wrong order, leading to a situation where URB (USB Request Block) callbacks attempt to access freed memory structures. The kernel's memory safety subsystem, KASAN, detected this violation when trying to read an 8-byte value from address ffff8881069132a0, which had already been freed. The stack trace reveals that the access occurs in ath9k_destroy_wmi, which is called after ieee80211_free_hw, but before URBs are properly terminated. This violates fundamental memory management principles and creates a potential vector for denial-of-service attacks or more severe exploits.
This vulnerability has significant operational impact on systems using the ath9k wireless driver, particularly those with USB-based wireless adapters. The use-after-free condition can lead to system crashes, kernel oops, or unpredictable behavior when USB wireless devices are disconnected. The flaw affects kernel versions that include the ath9k driver, potentially compromising the stability of network connectivity and system reliability. From an attacker perspective, this condition could be exploited to cause system instability or potentially escalate privileges through carefully crafted USB disconnection sequences, making it particularly concerning for embedded systems and devices where wireless connectivity is critical.
The fix implemented addresses the core issue by reordering the cleanup sequence to ensure that ath9k_destroy_wmi() is called before ieee80211_free_hw(). This ensures that all URB callbacks are terminated and their references to the WMI (Wireless Management Interface) structure are cleared before the memory is freed. The patch aligns with industry best practices for memory management in kernel space, where cleanup operations must be performed in reverse order of allocation to prevent dangling pointer references. This remediation follows CWE-416, which specifically addresses use-after-free vulnerabilities in software systems. The solution also aligns with ATT&CK framework technique T1059.006, which covers the exploitation of kernel vulnerabilities, though this particular fix prevents such exploitation rather than enabling it. The change is minimal and surgical, targeting only the problematic ordering without altering the broader driver functionality, ensuring system stability while eliminating the memory safety issue.