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List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6602:6b08:b0:943:5c83:d68e with SMTP id ca18e2360f4ac-94869cb498bmr905272739f.1.1762422330444; Thu, 06 Nov 2025 01:45:30 -0800 (PST) Date: Thu, 06 Nov 2025 01:45:30 -0800 In-Reply-To: <685d4c2a.a00a0220.2e5631.028c.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <690c6e3a.050a0220.3d0d33.0123.GAE@google.com> Subject: Re: [syzbot] [hams?] possible deadlock in nr_rt_ioctl (2) From: syzbot To: davem@davemloft.net, eadavis@qq.com, edumazet@google.com, hdanton@sina.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" syzbot has found a reproducer for the following issue on: HEAD commit: dc77806cf3b4 Merge tag 'rust-fixes-6.18' of git://git.kern.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=14c0e114580000 kernel config: https://syzkaller.appspot.com/x/.config?x=609c87dcb0628493 dashboard link: https://syzkaller.appspot.com/bug?extid=14afda08dc3484d5db82 compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17feb812580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15fb5812580000 Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-dc77806c.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/eef2d5e8c3fb/vmlinux-dc77806c.xz kernel image: https://storage.googleapis.com/syzbot-assets/e6323f5f18c6/bzImage-dc77806c.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+14afda08dc3484d5db82@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.0.18/6086 is trying to acquire lock: ffffffff9033ef98 (nr_neigh_list_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline] ffffffff9033ef98 (nr_neigh_list_lock){+...}-{3:3}, at: nr_remove_neigh net/netrom/nr_route.c:307 [inline] ffffffff9033ef98 (nr_neigh_list_lock){+...}-{3:3}, at: nr_del_node net/netrom/nr_route.c:342 [inline] ffffffff9033ef98 (nr_neigh_list_lock){+...}-{3:3}, at: nr_rt_ioctl+0x2007/0x29b0 net/netrom/nr_route.c:678 but task is already holding lock: ffff88802acfc870 (&nr_node->node_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline] ffff88802acfc870 (&nr_node->node_lock){+...}-{3:3}, at: nr_node_lock include/net/netrom.h:152 [inline] ffff88802acfc870 (&nr_node->node_lock){+...}-{3:3}, at: nr_del_node net/netrom/nr_route.c:335 [inline] ffff88802acfc870 (&nr_node->node_lock){+...}-{3:3}, at: nr_rt_ioctl+0x29d/0x29b0 net/netrom/nr_route.c:678 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&nr_node->node_lock){+...}-{3:3}: __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline] _raw_spin_lock_bh+0x33/0x40 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 net/netrom/nr_route.c:335 [inline] nr_rt_ioctl+0x29d/0x29b0 net/netrom/nr_route.c:678 nr_ioctl+0x19a/0x2d0 net/netrom/af_netrom.c:1254 sock_do_ioctl+0x118/0x280 net/socket.c:1254 sock_ioctl+0x227/0x6b0 net/socket.c:1375 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (nr_node_list_lock){+...}-{3:3}: __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline] _raw_spin_lock_bh+0x33/0x40 kernel/locking/spinlock.c:178 spin_lock_bh include/linux/spinlock.h:356 [inline] nr_rt_device_down+0xd3/0x810 net/netrom/nr_route.c:517 nr_device_event+0x126/0x170 net/netrom/af_netrom.c:126 notifier_call_chain+0xbc/0x410 kernel/notifier.c:85 call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2229 call_netdevice_notifiers_extack net/core/dev.c:2267 [inline] call_netdevice_notifiers net/core/dev.c:2281 [inline] netif_close_many+0x319/0x630 net/core/dev.c:1784 netif_close net/core/dev.c:1797 [inline] netif_close+0x17f/0x230 net/core/dev.c:1791 dev_close+0xaa/0x240 net/core/dev_api.c:220 bpq_device_event+0x6a9/0x910 drivers/net/hamradio/bpqether.c:528 notifier_call_chain+0xbc/0x410 kernel/notifier.c:85 call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2229 call_netdevice_notifiers_extack net/core/dev.c:2267 [inline] call_netdevice_notifiers net/core/dev.c:2281 [inline] netif_close_many+0x319/0x630 net/core/dev.c:1784 netif_close net/core/dev.c:1797 [inline] netif_close+0x17f/0x230 net/core/dev.c:1791 dev_close+0xaa/0x240 net/core/dev_api.c:220 bond_setup_by_slave drivers/net/bonding/bond_main.c:1567 [inline] bond_enslave+0x1e42/0x5de0 drivers/net/bonding/bond_main.c:1972 bond_do_ioctl+0x601/0x6c0 drivers/net/bonding/bond_main.c:4615 dev_siocbond net/core/dev_ioctl.c:516 [inline] dev_ifsioc+0xe9c/0x1f70 net/core/dev_ioctl.c:666 dev_ioctl+0x223/0x10e0 net/core/dev_ioctl.c:838 sock_do_ioctl+0x19d/0x280 net/socket.c:1268 sock_ioctl+0x227/0x6b0 net/socket.c:1375 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/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 kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline] _raw_spin_lock_bh+0x33/0x40 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 net/netrom/nr_route.c:342 [inline] nr_rt_ioctl+0x2007/0x29b0 net/netrom/nr_route.c:678 nr_ioctl+0x19a/0x2d0 net/netrom/af_netrom.c:1254 sock_do_ioctl+0x118/0x280 net/socket.c:1254 sock_ioctl+0x227/0x6b0 net/socket.c:1375 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/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.0.18/6086: #0: ffffffff9033eff8 (nr_node_list_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline] #0: ffffffff9033eff8 (nr_node_list_lock){+...}-{3:3}, at: nr_del_node net/netrom/nr_route.c:334 [inline] #0: ffffffff9033eff8 (nr_node_list_lock){+...}-{3:3}, at: nr_rt_ioctl+0x221/0x29b0 net/netrom/nr_route.c:678 #1: ffff88802acfc870 (&nr_node->node_lock){+...}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:356 [inline] #1: ffff88802acfc870 (&nr_node->node_lock){+...}-{3:3}, at: nr_node_lock include/net/netrom.h:152 [inline] #1: ffff88802acfc870 (&nr_node->node_lock){+...}-{3:3}, at: nr_del_node net/netrom/nr_route.c:335 [inline] #1: ffff88802acfc870 (&nr_node->node_lock){+...}-{3:3}, at: nr_rt_ioctl+0x29d/0x29b0 net/netrom/nr_route.c:678 stack backtrace: CPU: 3 UID: 0 PID: 6086 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 lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2043 check_noncircular+0x14c/0x170 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 kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline] _raw_spin_lock_bh+0x33/0x40 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 net/netrom/nr_route.c:342 [inline] nr_rt_ioctl+0x2007/0x29b0 net/netrom/nr_route.c:678 nr_ioctl+0x19a/0x2d0 net/netrom/af_netrom.c:1254 sock_do_ioctl+0x118/0x280 net/socket.c:1254 sock_ioctl+0x227/0x6b0 net/socket.c:1375 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f5a58b8f6c9 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:00007fff0134ba58 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f5a58de5fa0 RCX: 00007f5a58b8f6c9 RDX: 0000200000000680 RSI: 000000000000890c RDI: 000000000000000a RBP: 00007f5a58c11f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f5a58de5fa0 R14: 00007f5a58de5fa0 R15: 0000000000000003 --- 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.