CVE-2025-21729

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

wifi: rtw89: fix race between cancel_hw_scan and hw_scan completion

The rtwdev->scanning flag isnt protected by mutex originally, so cancel_hw_scan can pass the condition, but suddenly hw_scan completion unset the flag and calls ieee80211_scan_completed() that will free local->hw_scan_req. Then, cancel_hw_scan raises null-ptr-deref and use-after-free. Fix it by moving the check condition to where protected by mutex.

KASAN: null-ptr-deref in range [0x0000000000000088-0x000000000000008f] CPU: 2 PID: 6922 Comm: kworker/2:2 Tainted: G OE Hardware name: LENOVO 2356AD1/2356AD1, BIOS G7ETB6WW (2.76 ) 09/10/2019 Workqueue: events cfg80211_conn_work [cfg80211] RIP: 0010:rtw89_fw_h2c_scan_offload_be+0xc33/0x13c3 [rtw89_core] Code: 00 45 89 6c 24 1c 0f 85 23 01 00 00 48 8b 85 20 ff ff ff 48 8d RSP: 0018:ffff88811fd9f068 EFLAGS: 00010206 RAX: dffffc0000000000 RBX: ffff88811fd9f258 RCX: 0000000000000001 RDX: 0000000000000011 RSI: 0000000000000001 RDI: 0000000000000089 RBP: ffff88811fd9f170 R08: 0000000000000000 R09: 0000000000000000 R10: ffff88811fd9f108 R11: 0000000000000000 R12: ffff88810e47f960 R13: 0000000000000000 R14: 000000000000ffff R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8881d6f00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007531dfca55b0 CR3: 00000001be296004 CR4: 00000000001706e0 Call Trace: ? show_regs+0x61/0x73 ? __die_body+0x20/0x73 ? die_addr+0x4f/0x7b ? exc_general_protection+0x191/0x1db ? asm_exc_general_protection+0x27/0x30 ? rtw89_fw_h2c_scan_offload_be+0xc33/0x13c3 [rtw89_core] ? rtw89_fw_h2c_scan_offload_be+0x458/0x13c3 [rtw89_core] ? __pfx_rtw89_fw_h2c_scan_offload_be+0x10/0x10 [rtw89_core] ? do_raw_spin_lock+0x75/0xdb ? __pfx_do_raw_spin_lock+0x10/0x10 rtw89_hw_scan_offload+0xb5e/0xbf7 [rtw89_core] ? _raw_spin_unlock+0xe/0x24 ? __mutex_lock.constprop.0+0x40c/0x471 ? __pfx_rtw89_hw_scan_offload+0x10/0x10 [rtw89_core] ? __mutex_lock_slowpath+0x13/0x1f ? mutex_lock+0xa2/0xdc ? __pfx_mutex_lock+0x10/0x10 rtw89_hw_scan_abort+0x58/0xb7 [rtw89_core] rtw89_ops_cancel_hw_scan+0x120/0x13b [rtw89_core] ieee80211_scan_cancel+0x468/0x4d0 [mac80211] ieee80211_prep_connection+0x858/0x899 [mac80211] ieee80211_mgd_auth+0xbea/0xdde [mac80211] ? __pfx_ieee80211_mgd_auth+0x10/0x10 [mac80211] ? cfg80211_find_elem+0x15/0x29 [cfg80211] ? is_bss+0x1b7/0x1d7 [cfg80211] ieee80211_auth+0x18/0x27 [mac80211] cfg80211_mlme_auth+0x3bb/0x3e7 [cfg80211] cfg80211_conn_do_work+0x410/0xb81 [cfg80211] ? __pfx_cfg80211_conn_do_work+0x10/0x10 [cfg80211] ? __kasan_check_read+0x11/0x1f ? psi_group_change+0x8bc/0x944 ? __kasan_check_write+0x14/0x22 ? mutex_lock+0x8e/0xdc ? __pfx_mutex_lock+0x10/0x10 ? __pfx___radix_tree_lookup+0x10/0x10 cfg80211_conn_work+0x245/0x34d [cfg80211] ? __pfx_cfg80211_conn_work+0x10/0x10 [cfg80211] ? update_cfs_rq_load_avg+0x3bc/0x3d7 ? sched_clock_noinstr+0x9/0x1a ? sched_clock+0x10/0x24 ? sched_clock_cpu+0x7e/0x42e ? newidle_balance+0x796/0x937 ? __pfx_sched_clock_cpu+0x10/0x10 ? __pfx_newidle_balance+0x10/0x10 ? __kasan_check_read+0x11/0x1f ? psi_group_change+0x8bc/0x944 ? _raw_spin_unlock+0xe/0x24 ? raw_spin_rq_unlock+0x47/0x54 ? raw_spin_rq_unlock_irq+0x9/0x1f ? finish_task_switch.isra.0+0x347/0x586 ? __schedule+0x27bf/0x2892 ? mutex_unlock+0x80/0xd0 ? do_raw_spin_lock+0x75/0xdb ? __pfx___schedule+0x10/0x10 process_scheduled_works+0x58c/0x821 worker_thread+0x4c7/0x586 ? __kasan_check_read+0x11/0x1f kthread+0x285/0x294 ? __pfx_worker_thread+0x10/0x10 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x29/0x6f ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1b/0x30

Weakness

Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.

Affected Software

Extended Description

The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:

In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.

Potential Mitigations

References

• https://git.kernel.org/stable/c/2403cb3c235d5e339b580cc3a825493769fadca8
• https://git.kernel.org/stable/c/5afcd6fcd1e1c1fd6bcc9a360c121d10eddade67
• https://git.kernel.org/stable/c/ba4bb0402c60e945c4c396c51f0acac3c3e3ea5c