[v5.15] WARNING: suspicious RCU usage in cfg80211_bss_update

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 674f684f7c61 Linux 5.15.212
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=12651499580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f161cbc9aef65db0
dashboard link: https://syzkaller.appspot.com/bug?extid=e0acaf66a0a3c22177b6
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f55be2937b89/disk-674f684f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a19fb0ffc049/vmlinux-674f684f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/365d4529a007/bzImage-674f684f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e0acaf...@syzkaller.appspotmail.com

ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
=============================
WARNING: suspicious RCU usage
syzkaller #0 Not tainted
-----------------------------
net/wireless/scan.c:1845 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
5 locks held by kworker/u4:6/4333:
#0:
ffff888016c79138
(
(wq_completion)events_unbound
){+.+.}-{0:0}
, at: process_one_work+0x75c/0xff0 kernel/workqueue.c:-1
#1:
ffffc900046dfd00
(
(work_completion)(&rdev->wiphy_work)
){+.+.}-{0:0}
, at: process_one_work+0x79e/0xff0 kernel/workqueue.c:2285
#2:
ffff88807ab28688
(
&rdev->wiphy.mtx){+.+.}-{3:3}, at: wiphy_lock include/net/cfg80211.h:5319 [inline]
&rdev->wiphy.mtx){+.+.}-{3:3}, at: cfg80211_wiphy_work+0x31/0x260 net/wireless/core.c:420
#3:
ffff88802a3f8d40
(&wdev->mtx
){+.+.}-{3:3}
, at: sdata_lock net/mac80211/ieee80211_i.h:1036 [inline]
, at: ieee80211_ibss_work+0xa8/0x10f0 net/mac80211/ibss.c:1685
#4: ffff88807ab28168
(&rdev->bss_lock
){+...}-{2:2}
, at: spin_lock_bh include/linux/spinlock.h:369 [inline]
, at: cfg80211_bss_update+0x80/0x21a0 net/wireless/scan.c:1820

stack backtrace:
CPU: 1 PID: 4333 Comm: kworker/u4:6 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Workqueue: events_unbound cfg80211_wiphy_work
Call Trace:
<TASK>
dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
cfg80211_bss_update+0x95e/0x21a0 net/wireless/scan.c:1845
cfg80211_inform_single_bss_frame_data net/wireless/scan.c:2552 [inline]
cfg80211_inform_bss_frame_data+0x88d/0x1ed0 net/wireless/scan.c:2585
__ieee80211_sta_join_ibss+0xb23/0x1300 net/mac80211/ibss.c:389
ieee80211_sta_create_ibss+0x2c3/0x440 net/mac80211/ibss.c:1351
ieee80211_sta_find_ibss net/mac80211/ibss.c:1481 [inline]
ieee80211_ibss_work+0xdda/0x10f0 net/mac80211/ibss.c:1710
cfg80211_wiphy_work+0x224/0x260 net/wireless/core.c:433
process_one_work+0x867/0xff0 kernel/workqueue.c:2310
worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457
kthread+0x42e/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>

=============================
WARNING: suspicious RCU usage
syzkaller #0 Not tainted
-----------------------------
net/wireless/scan.c:1848 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
5 locks held by kworker/u4:6/4333:
#0:
ffff888016c79138
(
(wq_completion)events_unbound
){+.+.}-{0:0}
, at: process_one_work+0x75c/0xff0 kernel/workqueue.c:-1
#1:
ffffc900046dfd00
((work_completion)(&rdev->wiphy_work)
){+.+.}-{0:0}
, at: process_one_work+0x79e/0xff0 kernel/workqueue.c:2285
#2:
ffff88807ab28688
(
&rdev->wiphy.mtx
){+.+.}-{3:3}
, at: wiphy_lock include/net/cfg80211.h:5319 [inline]
, at: cfg80211_wiphy_work+0x31/0x260 net/wireless/core.c:420
#3: ffff88802a3f8d40
(&wdev->mtx
){+.+.}-{3:3}
, at: sdata_lock net/mac80211/ieee80211_i.h:1036 [inline]
, at: ieee80211_ibss_work+0xa8/0x10f0 net/mac80211/ibss.c:1685
#4:
ffff88807ab28168
(
&rdev->bss_lock
){+...}-{2:2}
, at: spin_lock_bh include/linux/spinlock.h:369 [inline]
, at: cfg80211_bss_update+0x80/0x21a0 net/wireless/scan.c:1820

stack backtrace:
CPU: 1 PID: 4333 Comm: kworker/u4:6 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Workqueue: events_unbound cfg80211_wiphy_work
Call Trace:
<TASK>
dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
cfg80211_bss_update+0x987/0x21a0 net/wireless/scan.c:1848
cfg80211_inform_single_bss_frame_data net/wireless/scan.c:2552 [inline]
cfg80211_inform_bss_frame_data+0x88d/0x1ed0 net/wireless/scan.c:2585
__ieee80211_sta_join_ibss+0xb23/0x1300 net/mac80211/ibss.c:389
ieee80211_sta_create_ibss+0x2c3/0x440 net/mac80211/ibss.c:1351
ieee80211_sta_find_ibss net/mac80211/ibss.c:1481 [inline]
ieee80211_ibss_work+0xdda/0x10f0 net/mac80211/ibss.c:1710
cfg80211_wiphy_work+0x224/0x260 net/wireless/core.c:433
process_one_work+0x867/0xff0 kernel/workqueue.c:2310
worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457
kthread+0x42e/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup