[syzbot] [net?] WARNING in __ethtool_get_link_ksettings

[syzbot] [net?] WARNING in __ethtool_get_link_ksettings

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    4fa3f5fabb30 Add linux-next specific files for 20260616
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1039ffec580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6c414e1864e61ef6
dashboard link: https://syzkaller.appspot.com/bug?extid=09da62a8b78959ceb8bb
compiler:       Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bf5b803a695d/disk-4fa3f5fa.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/47871e7c589e/vmlinux-4fa3f5fa.xz
kernel image: https://storage.googleapis.com/syzbot-assets/53cd9ef32a2b/bzImage-4fa3f5fa.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+09da62a8b78959ceb8bb@syzkaller.appspotmail.com

netlink: 'syz.3.4736': attribute type 10 has an invalid length.
------------[ cut here ]------------
rtmutex deadlock detected
WARNING: kernel/locking/rtmutex.c:1698 at rt_mutex_handle_deadlock+0x21/0xb0 kernel/locking/rtmutex.c:1698, CPU#0: syz.3.4736/19861
Modules linked in:
CPU: 0 UID: 0 PID: 19861 Comm: syz.3.4736 Tainted: G             L      syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:rt_mutex_handle_deadlock+0x21/0xb0 kernel/locking/rtmutex.c:1698
Code: 90 90 90 90 90 90 90 90 90 41 57 41 56 41 55 41 54 53 83 ff dd 0f 85 81 00 00 00 48 89 f7 e8 16 40 01 00 48 8d 3d 3f 2f 5d 04 <67> 48 0f b9 3a 4c 8d 3d 00 00 00 00 65 48 8b 1d 13 2d 42 07 4c 8d
RSP: 0018:ffffc90003d760f0 EFLAGS: 00010286
RAX: 0000000080000000 RBX: 00000000ffffffdd RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8baa3a60 RDI: ffffffff8f8fd220
RBP: ffffc90003d762a0 R08: ffffffff8f8c5ff7 R09: 1ffffffff1f18bfe
R10: dffffc0000000000 R11: fffffbfff1f18bff R12: 1ffff920007aec2c
R13: ffffffff8b329d22 R14: ffff88805dbb1008 R15: dffffc0000000000
FS:  00007fd5506ae6c0(0000) GS:ffff888125ed3000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000003cd08000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __rt_mutex_slowlock kernel/locking/rtmutex.c:1760 [inline]
 __rt_mutex_slowlock_locked kernel/locking/rtmutex.c:1787 [inline]
 rt_mutex_slowlock+0x73c/0x780 kernel/locking/rtmutex.c:1827
 __rt_mutex_lock kernel/locking/rtmutex.c:1842 [inline]
 __mutex_lock_common kernel/locking/rtmutex_api.c:560 [inline]
 mutex_lock_nested+0x168/0x1d0 kernel/locking/rtmutex_api.c:578
 netdev_lock include/linux/netdevice.h:2846 [inline]
 netdev_lock_ops include/net/netdev_lock.h:42 [inline]
 __ethtool_get_link_ksettings+0x109/0x250 net/ethtool/ioctl.c:463
 bond_update_speed_duplex drivers/net/bonding/bond_main.c:801 [inline]
 bond_slave_netdev_event drivers/net/bonding/bond_main.c:3982 [inline]
 bond_netdev_event+0x643/0xf80 drivers/net/bonding/bond_main.c:4089
 notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2289 [inline]
 call_netdevice_notifiers net/core/dev.c:2303 [inline]
 __dev_notify_flags+0x1aa/0x310 net/core/dev.c:9792
 netif_change_flags+0xde/0x1b0 net/core/dev.c:9821
 dev_change_flags+0x128/0x260 net/core/dev_api.c:68
 vlan_device_event+0x1b4e/0x1f00 net/8021q/vlan.c:494
 notifier_call_chain+0x1a5/0x3d0 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2289 [inline]
 call_netdevice_notifiers net/core/dev.c:2303 [inline]
 netif_open+0x10f/0x190 net/core/dev.c:1730
 dev_open+0x101/0x220 net/core/dev_api.c:202
 bond_enslave+0xeb2/0x3b70 drivers/net/bonding/bond_main.c:2089
 do_set_master+0x563/0x720 net/core/rtnetlink.c:3012
 do_setlink+0xe7b/0x4670 net/core/rtnetlink.c:3214
 rtnl_changelink net/core/rtnetlink.c:3841 [inline]
 __rtnl_newlink net/core/rtnetlink.c:4014 [inline]
 rtnl_newlink+0x15c2/0x1bd0 net/core/rtnetlink.c:4151
 rtnetlink_rcv_msg+0x802/0xc00 net/core/rtnetlink.c:7068
 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2556
 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
 netlink_unicast+0x7f5/0x990 net/netlink/af_netlink.c:1345
 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1900
 sock_sendmsg_nosec+0x13a/0x180 net/socket.c:785
 __sock_sendmsg net/socket.c:800 [inline]
 ____sys_sendmsg+0x565/0x870 net/socket.c:2702
 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2756
 __sys_sendmsg net/socket.c:2788 [inline]
 __do_sys_sendmsg net/socket.c:2793 [inline]
 __se_sys_sendmsg net/socket.c:2791 [inline]
 __x64_sys_sendmsg+0x1b7/0x290 net/socket.c:2791
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd55245ce59
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:00007fd5506ae028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fd5526d5fa0 RCX: 00007fd55245ce59
RDX: 0000000000008084 RSI: 0000200000000600 RDI: 0000000000000003
RBP: 00007fd5524f2d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd5526d6038 R14: 00007fd5526d5fa0 R15: 00007ffdbadd34a8
 </TASK>
----------------
Code disassembly (best guess):
   0:	90                   	nop
   1:	90                   	nop
   2:	90                   	nop
   3:	90                   	nop
   4:	90                   	nop
   5:	90                   	nop
   6:	90                   	nop
   7:	90                   	nop
   8:	90                   	nop
   9:	41 57                	push   %r15
   b:	41 56                	push   %r14
   d:	41 55                	push   %r13
   f:	41 54                	push   %r12
  11:	53                   	push   %rbx
  12:	83 ff dd             	cmp    $0xffffffdd,%edi
  15:	0f 85 81 00 00 00    	jne    0x9c
  1b:	48 89 f7             	mov    %rsi,%rdi
  1e:	e8 16 40 01 00       	call   0x14039
  23:	48 8d 3d 3f 2f 5d 04 	lea    0x45d2f3f(%rip),%rdi        # 0x45d2f69
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	4c 8d 3d 00 00 00 00 	lea    0x0(%rip),%r15        # 0x36
  36:	65 48 8b 1d 13 2d 42 	mov    %gs:0x7422d13(%rip),%rbx        # 0x7422d51
  3d:	07
  3e:	4c                   	rex.WR
  3f:	8d                   	.byte 0x8d


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