syzbot

netdevsim netdevsim4 netdevsim0: unset [1, 0] type 2 family 0 port 6081 - 0
============================================
WARNING: possible recursive locking detected
6.16.0-rc6-syzkaller-00002-g155a3c003e55 #0 Not tainted
--------------------------------------------
syz.4.1836/13568 is trying to acquire lock:
ffff88807c800d30 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2756 [inline]
ffff88807c800d30 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: netdev_lock_ops include/net/netdev_lock.h:42 [inline]
ffff88807c800d30 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: netdev_sync_lower_features net/core/dev.c:10550 [inline]
ffff88807c800d30 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: __netdev_update_features+0xcb1/0x1a20 net/core/dev.c:10720

but task is already holding lock:
ffff88807c800d30 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2756 [inline]
ffff88807c800d30 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: netdev_lock_ops include/net/netdev_lock.h:42 [inline]
ffff88807c800d30 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: __dev_ethtool net/ethtool/ioctl.c:3228 [inline]
ffff88807c800d30 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: dev_ethtool+0x716/0x1990 net/ethtool/ioctl.c:3491
and the lock comparison function returns 0:

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&dev_instance_lock_key#20);
  lock(&dev_instance_lock_key#20);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

2 locks held by syz.4.1836/13568:
 #0: ffffffff8f51da08 (rtnl_mutex){+.+.}-{4:4}, at: dev_ethtool+0x1d0/0x1990 net/ethtool/ioctl.c:3490
 #1: ffff88807c800d30 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2756 [inline]
 #1: ffff88807c800d30 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: netdev_lock_ops include/net/netdev_lock.h:42 [inline]
 #1: ffff88807c800d30 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: __dev_ethtool net/ethtool/ioctl.c:3228 [inline]
 #1: ffff88807c800d30 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: dev_ethtool+0x716/0x1990 net/ethtool/ioctl.c:3491

stack backtrace:
CPU: 0 UID: 0 PID: 13568 Comm: syz.4.1836 Not tainted 6.16.0-rc6-syzkaller-00002-g155a3c003e55 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_deadlock_bug+0x28b/0x2a0 kernel/locking/lockdep.c:3044
 check_deadlock kernel/locking/lockdep.c:3096 [inline]
 validate_chain+0x1a3f/0x2140 kernel/locking/lockdep.c:3898
 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
 __mutex_lock_common kernel/locking/mutex.c:602 [inline]
 __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:747
 netdev_lock include/linux/netdevice.h:2756 [inline]
 netdev_lock_ops include/net/netdev_lock.h:42 [inline]
 netdev_sync_lower_features net/core/dev.c:10550 [inline]
 __netdev_update_features+0xcb1/0x1a20 net/core/dev.c:10720
 netdev_update_features+0x6d/0xe0 net/core/dev.c:10775
 macsec_notify+0x2f5/0x660 drivers/net/macsec.c:4533
 notifier_call_chain+0x1b3/0x3e0 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2268 [inline]
 call_netdevice_notifiers net/core/dev.c:2282 [inline]
 netdev_features_change+0x85/0xc0 net/core/dev.c:1571
 __dev_ethtool net/ethtool/ioctl.c:3458 [inline]
 dev_ethtool+0x1520/0x1990 net/ethtool/ioctl.c:3491
 dev_ioctl+0x392/0x1150 net/core/dev_ioctl.c:758
 sock_do_ioctl+0x22c/0x300 net/socket.c:1204
 sock_ioctl+0x576/0x790 net/socket.c:1311
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f683418e929
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6835018038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f68343b5fa0 RCX: 00007f683418e929
RDX: 0000200000000080 RSI: 0000000000008946 RDI: 0000000000000027
RBP: 00007f6834210b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f68343b5fa0 R15: 00007f68344dfa28
 </TASK>