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006d021491bc7-661179db260mr412053eaf.66.1768508783780; Thu, 15 Jan 2026 12:26:23 -0800 (PST) Date: Thu, 15 Jan 2026 12:26:23 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69694d6f.050a0220.58bed.0028.GAE@google.com> Subject: [syzbot] [hams?] possible deadlock in nr_del_node (2) From: syzbot To: davem@davemloft.net, edumazet@google.com, horms@kernel.org, kuba@kernel.org, linux-hams@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 4427259cc7f7 Merge tag 'riscv-for-linus-6.18-rc6' of git:/.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=13eadc12580000 kernel config: https://syzkaller.appspot.com/x/.config?x=929790bc044e87d7 dashboard link: https://syzkaller.appspot.com/bug?extid=6eb7834837cf6a8db75b compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=125eb0b4580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15f3f17c580000 Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-4427259c.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/5a19e3326bed/vmlinux-4427259c.xz kernel image: https://storage.googleapis.com/syzbot-assets/582f300a9de8/bzImage-4427259c.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+6eb7834837cf6a8db75b@syzkaller.appspotmail.com 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: 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 --- 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 syzkaller@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 syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing. 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