[v6.6] WARNING: suspicious RCU usage in ieee80211_check_concurrent_iface

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 1b4ef5214f17 Linux 6.6.124
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15ba7402580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2a950bf7c0bff9f9
dashboard link: https://syzkaller.appspot.com/bug?extid=95df812296710ce46e07
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/054222c95938/disk-1b4ef521.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bf3f638dea81/vmlinux-1b4ef521.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ba2200fbe5c9/bzImage-1b4ef521.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+95df81...@syzkaller.appspotmail.com

=============================
WARNING: suspicious RCU usage
syzkaller #0 Not tainted
-----------------------------
net/mac80211/iface.c:378 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz.8.6051/30507:
#0: ffffffff8e3c0208 (rtnl_mutex){+.+.}-{3:3}, at: dev_ioctl+0x7a4/0x1140 net/core/dev_ioctl.c:769

stack backtrace:
CPU: 1 PID: 30507 Comm: syz.8.6051 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
Call Trace:
<TASK>
dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
lockdep_rcu_suspicious+0x1e1/0x300 kernel/locking/lockdep.c:6731
ieee80211_check_concurrent_iface+0x475/0x950 net/mac80211/iface.c:378
ieee80211_open+0xc1/0x200 net/mac80211/iface.c:466
__dev_open+0x2cb/0x430 net/core/dev.c:1519
__dev_change_flags+0x211/0x6a0 net/core/dev.c:8698
dev_change_flags+0x88/0x1a0 net/core/dev.c:8770
dev_ioctl+0x7b4/0x1140 net/core/dev_ioctl.c:770
sock_do_ioctl+0x239/0x310 net/socket.c:1233
sock_ioctl+0x5ba/0x7e0 net/socket.c:1340
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f6b6399bf79
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6b648c8028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f6b63c15fa0 RCX: 00007f6b6399bf79
RDX: 0000200000002280 RSI: 0000000000008914 RDI: 0000000000000003
RBP: 00007f6b63a327e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6b63c16038 R14: 00007f6b63c15fa0 R15: 00007ffd9abe9188
</TASK>


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 1b4ef5214f17 Linux 6.6.124
git tree: linux-6.6.y

console output: https://syzkaller.appspot.com/x/log.txt?x=10f40652580000

kernel config: https://syzkaller.appspot.com/x/.config?x=2a950bf7c0bff9f9
dashboard link: https://syzkaller.appspot.com/bug?extid=95df812296710ce46e07
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13104722580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14b5a6e6580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/054222c95938/disk-1b4ef521.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bf3f638dea81/vmlinux-1b4ef521.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ba2200fbe5c9/bzImage-1b4ef521.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+95df81...@syzkaller.appspotmail.com

=============================
WARNING: suspicious RCU usage
syzkaller #0 Not tainted
-----------------------------
net/mac80211/iface.c:378 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1

1 lock held by syz.0.17/5930:

#0: ffffffff8e3c0208 (rtnl_mutex){+.+.}-{3:3}, at: dev_ioctl+0x7a4/0x1140 net/core/dev_ioctl.c:769

stack backtrace:

CPU: 1 PID: 5930 Comm: syz.0.17 Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
Call Trace:
<TASK>
dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
lockdep_rcu_suspicious+0x1e1/0x300 kernel/locking/lockdep.c:6731
ieee80211_check_concurrent_iface+0x475/0x950 net/mac80211/iface.c:378
ieee80211_open+0xc1/0x200 net/mac80211/iface.c:466
__dev_open+0x2cb/0x430 net/core/dev.c:1519
__dev_change_flags+0x211/0x6a0 net/core/dev.c:8698
dev_change_flags+0x88/0x1a0 net/core/dev.c:8770
dev_ioctl+0x7b4/0x1140 net/core/dev_ioctl.c:770
sock_do_ioctl+0x239/0x310 net/socket.c:1233
sock_ioctl+0x5ba/0x7e0 net/socket.c:1340
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0xfd/0x170 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2

RIP: 0033:0x7f8cea59bf79

Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48

RSP: 002b:00007ffc2a106c08 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f8cea815fa0 RCX: 00007f8cea59bf79
RDX: 0000200000002280 RSI: 0000000000008914 RDI: 0000000000000004
RBP: 00007f8cea6327e0 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007f8cea815fac R14: 00007f8cea815fa0 R15: 00007f8cea815fa0
</TASK>
mac80211_hwsim hwsim4 syzkaller0: entered promiscuous mode
mac80211_hwsim hwsim4 syzkaller0: entered allmulticast mode


---
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