syzbot


possible deadlock in nr_del_node (2)

Status: upstream: reported C repro on 2026/01/15 20:26
Subsystems: hams
[Documentation on labels]
Reported-by: syzbot+6eb7834837cf6a8db75b@syzkaller.appspotmail.com
First crash: 427d, last: 2d17h
Cause bisection: failed (error log, bisect log)
  
Discussions (3)
Title Replies (including bot) Last reply
[syzbot] Monthly hams report (Feb 2026) 0 (1) 2026/02/26 12:58
[syzbot] Monthly hams report (Jan 2026) 0 (1) 2026/01/26 07:12
[syzbot] [hams?] possible deadlock in nr_del_node (2) 0 (1) 2026/01/15 20:26
Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 possible deadlock in nr_del_node 4 2 397d 427d 0/3 auto-obsoleted due to no activity on 2025/05/12 01:18
linux-6.1 possible deadlock in nr_del_node (2) 4 1 222d 222d 0/3 auto-obsoleted due to no activity on 2025/11/02 10:34
linux-6.6 possible deadlock in nr_del_node 4 1 222d 222d 0/2 auto-obsoleted due to no activity on 2025/11/02 18:54
linux-5.15 possible deadlock in nr_del_node origin:upstream 4 C error 3 33d 306d 0/3 upstream: reported C repro on 2025/05/02 21:19
Last patch testing requests (6)
Created Duration User Patch Repo Result
2026/02/10 05:24 16m retest repro upstream log
2025/12/25 06:12 21m retest repro linux-next report log
2025/08/20 18:14 2h40m retest repro linux-next report log
2025/08/20 18:07 20m retest repro upstream OK log
2025/06/02 21:27 9m retest repro upstream report log
2025/03/07 16:44 15m retest repro upstream report log

Sample crash report:
bond0: (slave rose0): Error: Device is in use and cannot be enslaved
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.18/5503 is trying to acquire lock:
ffffffff8f428318 (nr_neigh_list_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffffffff8f428318 (nr_neigh_list_lock){+...}-{3:3}, at: nr_remove_neigh net/netrom/nr_route.c:307 [inline]
ffffffff8f428318 (nr_neigh_list_lock){+...}-{3:3}, at: nr_del_node+0x517/0x8d0 net/netrom/nr_route.c:342

but task is already holding lock:
ffff88804c3b2c70 (&nr_node->node_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff88804c3b2c70 (&nr_node->node_lock){+...}-{3:3}, at: nr_node_lock include/net/netrom.h:152 [inline]
ffff88804c3b2c70 (&nr_node->node_lock){+...}-{3:3}, at: nr_del_node+0x152/0x8d0 net/netrom/nr_route.c:335

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&nr_node->node_lock){+...}-{3:3}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
       _raw_spin_lock_bh+0x36/0x50 kernel/locking/spinlock.c:178
       spin_lock_bh include/linux/spinlock.h:356 [inline]
       nr_node_lock include/net/netrom.h:152 [inline]
       nr_del_node+0x152/0x8d0 net/netrom/nr_route.c:335
       nr_rt_ioctl+0x989/0xd50 net/netrom/nr_route.c:678
       sock_do_ioctl+0xdc/0x300 net/socket.c:1254
       sock_ioctl+0x576/0x790 net/socket.c:1375
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (nr_node_list_lock){+...}-{3:3}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
       _raw_spin_lock_bh+0x36/0x50 kernel/locking/spinlock.c:178
       spin_lock_bh include/linux/spinlock.h:356 [inline]
       nr_rt_device_down+0xa9/0x720 net/netrom/nr_route.c:517
       nr_device_event+0x137/0x150 net/netrom/af_netrom.c:126
       notifier_call_chain+0x1b6/0x3e0 kernel/notifier.c:85
       call_netdevice_notifiers_extack net/core/dev.c:2267 [inline]
       call_netdevice_notifiers net/core/dev.c:2281 [inline]
       netif_close_many+0x29c/0x410 net/core/dev.c:1784
       netif_close+0x158/0x210 net/core/dev.c:1797
       dev_close+0x10a/0x220 net/core/dev_api.c:220
       bpq_device_event+0x377/0x6a0 drivers/net/hamradio/bpqether.c:528
       notifier_call_chain+0x1b6/0x3e0 kernel/notifier.c:85
       call_netdevice_notifiers_extack net/core/dev.c:2267 [inline]
       call_netdevice_notifiers net/core/dev.c:2281 [inline]
       netif_close_many+0x29c/0x410 net/core/dev.c:1784
       netif_close+0x158/0x210 net/core/dev.c:1797
       dev_close+0x10a/0x220 net/core/dev_api.c:220
       bond_setup_by_slave+0x5f/0x3f0 drivers/net/bonding/bond_main.c:1567
       bond_enslave+0x6ca/0x3850 drivers/net/bonding/bond_main.c:1972
       bond_do_ioctl+0x635/0x9b0 drivers/net/bonding/bond_main.c:4615
       dev_siocbond net/core/dev_ioctl.c:516 [inline]
       dev_ifsioc+0x90b/0xf00 net/core/dev_ioctl.c:666
       dev_ioctl+0x7b4/0x1150 net/core/dev_ioctl.c:838
       sock_do_ioctl+0x22c/0x300 net/socket.c:1268
       sock_ioctl+0x576/0x790 net/socket.c:1375
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (nr_neigh_list_lock){+...}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
       __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
       _raw_spin_lock_bh+0x36/0x50 kernel/locking/spinlock.c:178
       spin_lock_bh include/linux/spinlock.h:356 [inline]
       nr_remove_neigh net/netrom/nr_route.c:307 [inline]
       nr_del_node+0x517/0x8d0 net/netrom/nr_route.c:342
       nr_rt_ioctl+0x989/0xd50 net/netrom/nr_route.c:678
       sock_do_ioctl+0xdc/0x300 net/socket.c:1254
       sock_ioctl+0x576/0x790 net/socket.c:1375
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  nr_neigh_list_lock --> nr_node_list_lock --> &nr_node->node_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&nr_node->node_lock);
                               lock(nr_node_list_lock);
                               lock(&nr_node->node_lock);
  lock(nr_neigh_list_lock);

 *** DEADLOCK ***

2 locks held by syz.0.18/5503:
 #0: ffffffff8f428378 (nr_node_list_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
 #0: ffffffff8f428378 (nr_node_list_lock){+...}-{3:3}, at: nr_del_node+0xfc/0x8d0 net/netrom/nr_route.c:334
 #1: ffff88804c3b2c70 (&nr_node->node_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
 #1: ffff88804c3b2c70 (&nr_node->node_lock){+...}-{3:3}, at: nr_node_lock include/net/netrom.h:152 [inline]
 #1: ffff88804c3b2c70 (&nr_node->node_lock){+...}-{3:3}, at: nr_del_node+0x152/0x8d0 net/netrom/nr_route.c:335

stack backtrace:
CPU: 0 UID: 0 PID: 5503 Comm: syz.0.18 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043
 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908
 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
 _raw_spin_lock_bh+0x36/0x50 kernel/locking/spinlock.c:178
 spin_lock_bh include/linux/spinlock.h:356 [inline]
 nr_remove_neigh net/netrom/nr_route.c:307 [inline]
 nr_del_node+0x517/0x8d0 net/netrom/nr_route.c:342
 nr_rt_ioctl+0x989/0xd50 net/netrom/nr_route.c:678
 sock_do_ioctl+0xdc/0x300 net/socket.c:1254
 sock_ioctl+0x576/0x790 net/socket.c:1375
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc3e5b8f6c9
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:00007ffe09c753a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fc3e5de5fa0 RCX: 00007fc3e5b8f6c9
RDX: 0000200000000680 RSI: 000000000000890c RDI: 000000000000000a
RBP: 00007fc3e5c11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc3e5de5fa0 R14: 00007fc3e5de5fa0 R15: 0000000000000003
 </TASK>

Crashes (164):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/11 13:38 upstream 4427259cc7f7 4e1406b4 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root possible deadlock in nr_del_node
2026/02/17 01:21 net ee5492fd88cf 5d52cba5 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2025/07/27 07:45 linux-next d086c886ceb9 fb8f743d .config strace log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce possible deadlock in nr_del_node
2025/07/31 17:19 upstream 038d61fd6422 0c075d67 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root possible deadlock in nr_del_node
2025/07/31 05:14 upstream e8d780dcd957 f8f2b4da .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root possible deadlock in nr_del_node
2025/12/06 02:00 upstream d1d36025a617 d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root possible deadlock in nr_del_node
2025/02/21 16:28 upstream 334426094588 0808a665 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root possible deadlock in nr_del_node
2026/03/02 09:13 net 9439a661c2e8 43249bac .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/27 06:09 net b9c8fc2caea6 a2f13f71 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/26 04:39 net 7c9db1a1cd3b e0f78d93 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/26 01:38 net 2f61f38a2174 e0f78d93 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/26 01:38 net 2f61f38a2174 e0f78d93 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/25 11:58 net 1348659dc92e 787dfb7c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/25 08:30 net 1348659dc92e 787dfb7c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/25 07:30 net 1348659dc92e 787dfb7c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/25 06:01 net 1348659dc92e 787dfb7c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/25 04:51 net 1348659dc92e 787dfb7c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/24 23:14 net 3d7e6ce34f4f 96b1aa46 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/24 18:33 net 3d7e6ce34f4f 96b1aa46 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/23 14:25 net d4f687fbbce4 305c0ec5 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/23 11:23 net d4f687fbbce4 305c0ec5 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/23 08:13 net d4f687fbbce4 6e7b5511 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/23 06:33 net d4f687fbbce4 6e7b5511 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/23 05:23 net d4f687fbbce4 6e7b5511 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/22 22:39 net d4f687fbbce4 6e7b5511 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/22 16:04 net d4f687fbbce4 6e7b5511 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/22 01:34 net d4f687fbbce4 6e7b5511 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/21 18:14 net d4f687fbbce4 6e7b5511 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/21 01:40 net bfd264fbbbca 741f5161 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/11 01:34 net 3a23b80dd72d 441e25b7 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/01/27 05:09 net 8d7ba71e4621 efb3e894 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/01/25 04:27 net 8016dc5ee19a 40acda8a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/01/25 01:48 net 8016dc5ee19a 40acda8a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/01/16 18:24 net a74c7a58ca2c d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/01/16 03:38 net 851822aec1a3 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/01/15 16:53 net 4156c3745f06 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/01/10 08:16 net 7470a7a63dc1 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/01/06 14:22 net d96bfb686742 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/01/06 11:48 net d96bfb686742 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/01/06 09:35 net d96bfb686742 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/01/06 08:17 net d96bfb686742 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2025/12/30 17:13 net 58fc7342b529 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2025/12/11 06:08 net 6bcb7727d9e6 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2025/12/09 08:02 net 0373d5c387f2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2025/12/08 14:38 net 0373d5c387f2 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2025/12/02 21:20 net 108f9405ce81 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2025/11/20 14:43 net 3ceb6ac2116e 280ea308 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2025/11/20 01:13 net e31a11be41cd 26ee5237 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2025/11/19 18:37 net 106a67494c53 26ee5237 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2025/11/19 15:16 net 106a67494c53 26ee5237 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2025/11/15 12:32 net 5442a9da6978 f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce possible deadlock in nr_del_node
2026/02/10 09:12 net-next 71e1eab8d246 4ab09a02 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce possible deadlock in nr_del_node
2026/01/23 18:58 net-next 9abf22075da9 3181850c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce possible deadlock in nr_del_node
2025/11/19 11:04 net-next d7dbda878920 ef766cd7 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce possible deadlock in nr_del_node
2025/07/26 06:27 linux-next d086c886ceb9 fb8f743d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce possible deadlock in nr_del_node
2025/07/24 21:12 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 82af5ea7c611 fb8f743d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 possible deadlock in nr_del_node
* Struck through repros no longer work on HEAD.