syzbot


possible deadlock in xsk_notifier (3)

Status: upstream: reported on 2025/06/24 18:51
Subsystems: bpf net
[Documentation on labels]
Reported-by: syzbot+e67ea9c235b13b4f0020@syzkaller.appspotmail.com
Fix commit: 53898ebabe84 net: lapbether: ignore ops-locked netdevs
Patched on: [ci-qemu-gce-upstream-auto ci-qemu-native-arm64-kvm ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-snapshot-upstream-root ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-arm64 ci-upstream-gce-leak ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root ci-upstream-linux-next-kasan-gce-root ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci-upstream-rust-kasan-gce ci2-upstream-fs ci2-upstream-kcsan-gce ci2-upstream-usb], missing on: [ci-qemu2-riscv64]
First crash: 92d, last: 42d
Discussions (2)
Title Replies (including bot) Last reply
[PATCH net 1/2] net: lapbether: ignore ops-locked netdevs 3 (3) 2025/08/08 20:50
[syzbot] [bpf?] [net?] possible deadlock in xsk_notifier (3) 8 (9) 2025/06/26 00:24
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream possible deadlock in xsk_notifier (2) bpf net 4 5 162d 166d 29/29 closed as dup on 2025/04/12 22:10
upstream possible deadlock in xsk_notifier bpf net 4 C done 495 2259d 2271d 12/29 fixed on 2019/08/14 02:14

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
6.17.0-rc1-syzkaller-00029-g91325f31afc1 #0 Not tainted
------------------------------------------------------
dhcpcd/5522 is trying to acquire lock:
ffffffff99fc2398 (&net->xdp.lock){+.+.}-{4:4}, at: xsk_notifier+0x89/0x230 net/xdp/xsk.c:1664

but task is already holding lock:
ffff888062718d28 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2758 [inline]
ffff888062718d28 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: netdev_lock_ops include/net/netdev_lock.h:42 [inline]
ffff888062718d28 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: dev_change_flags+0x113/0x260 net/core/dev_api.c:67

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&dev_instance_lock_key#20){+.+.}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       __mutex_lock_common kernel/locking/mutex.c:598 [inline]
       __mutex_lock+0x187/0x1360 kernel/locking/mutex.c:760
       netdev_lock include/linux/netdevice.h:2758 [inline]
       netdev_lock_ops include/net/netdev_lock.h:42 [inline]
       xsk_bind+0x2f7/0xf90 net/xdp/xsk.c:1193
       __sys_bind_socket net/socket.c:1858 [inline]
       __sys_bind+0x2c6/0x3e0 net/socket.c:1889
       __do_sys_bind net/socket.c:1894 [inline]
       __se_sys_bind net/socket.c:1892 [inline]
       __x64_sys_bind+0x7a/0x90 net/socket.c:1892
       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

-> #1 (&xs->mutex){+.+.}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
       __mutex_lock_common kernel/locking/mutex.c:598 [inline]
       __mutex_lock+0x187/0x1360 kernel/locking/mutex.c:760
       xsk_notifier+0xd5/0x230 net/xdp/xsk.c:1668
       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]
       unregister_netdevice_many_notify+0x14d7/0x1ff0 net/core/dev.c:12148
       rtnl_delete_link net/core/rtnetlink.c:3513 [inline]
       rtnl_dellink+0x488/0x710 net/core/rtnetlink.c:3555
       rtnetlink_rcv_msg+0x7cf/0xb70 net/core/rtnetlink.c:6946
       netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2552
       netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
       netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1346
       netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1896
       sock_sendmsg_nosec net/socket.c:714 [inline]
       __sock_sendmsg+0x21c/0x270 net/socket.c:729
       ____sys_sendmsg+0x505/0x830 net/socket.c:2614
       ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2668
       __sys_sendmsg net/socket.c:2700 [inline]
       __do_sys_sendmsg net/socket.c:2705 [inline]
       __se_sys_sendmsg net/socket.c:2703 [inline]
       __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2703
       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

-> #0 (&net->xdp.lock){+.+.}-{4:4}:
       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
       __mutex_lock_common kernel/locking/mutex.c:598 [inline]
       __mutex_lock+0x187/0x1360 kernel/locking/mutex.c:760
       xsk_notifier+0x89/0x230 net/xdp/xsk.c:1664
       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]
       unregister_netdevice_many_notify+0x14d7/0x1ff0 net/core/dev.c:12148
       unregister_netdevice_many net/core/dev.c:12211 [inline]
       unregister_netdevice_queue+0x33c/0x380 net/core/dev.c:12055
       register_netdevice+0x1689/0x1ae0 net/core/dev.c:11233
       bpq_new_device drivers/net/hamradio/bpqether.c:481 [inline]
       bpq_device_event+0x491/0x600 drivers/net/hamradio/bpqether.c:523
       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]
       __dev_notify_flags+0x18d/0x2e0 net/core/dev.c:-1
       netif_change_flags+0xe8/0x1a0 net/core/dev.c:9600
       dev_change_flags+0x130/0x260 net/core/dev_api.c:68
       devinet_ioctl+0xbb4/0x1b50 net/ipv4/devinet.c:1200
       inet_ioctl+0x3c0/0x4c0 net/ipv4/af_inet.c:1001
       sock_do_ioctl+0xdc/0x300 net/socket.c:1238
       sock_ioctl+0x576/0x790 net/socket.c:1359
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:598 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:584
       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

other info that might help us debug this:

Chain exists of:
  &net->xdp.lock --> &xs->mutex --> &dev_instance_lock_key#20

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&dev_instance_lock_key#20);
                               lock(&xs->mutex);
                               lock(&dev_instance_lock_key#20);
  lock(&net->xdp.lock);

 *** DEADLOCK ***

2 locks held by dhcpcd/5522:
 #0: ffffffff8f537c88 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
 #0: ffffffff8f537c88 (rtnl_mutex){+.+.}-{4:4}, at: devinet_ioctl+0x323/0x1b50 net/ipv4/devinet.c:1121
 #1: ffff888062718d28 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2758 [inline]
 #1: ffff888062718d28 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: netdev_lock_ops include/net/netdev_lock.h:42 [inline]
 #1: ffff888062718d28 (&dev_instance_lock_key#20){+.+.}-{4:4}, at: dev_change_flags+0x113/0x260 net/core/dev_api.c:67

stack backtrace:
CPU: 1 UID: 0 PID: 5522 Comm: dhcpcd Not tainted 6.17.0-rc1-syzkaller-00029-g91325f31afc1 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
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
 __mutex_lock_common kernel/locking/mutex.c:598 [inline]
 __mutex_lock+0x187/0x1360 kernel/locking/mutex.c:760
 xsk_notifier+0x89/0x230 net/xdp/xsk.c:1664
 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]
 unregister_netdevice_many_notify+0x14d7/0x1ff0 net/core/dev.c:12148
 unregister_netdevice_many net/core/dev.c:12211 [inline]
 unregister_netdevice_queue+0x33c/0x380 net/core/dev.c:12055
 register_netdevice+0x1689/0x1ae0 net/core/dev.c:11233
 bpq_new_device drivers/net/hamradio/bpqether.c:481 [inline]
 bpq_device_event+0x491/0x600 drivers/net/hamradio/bpqether.c:523
 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]
 __dev_notify_flags+0x18d/0x2e0 net/core/dev.c:-1
 netif_change_flags+0xe8/0x1a0 net/core/dev.c:9600
 dev_change_flags+0x130/0x260 net/core/dev_api.c:68
 devinet_ioctl+0xbb4/0x1b50 net/ipv4/devinet.c:1200
 inet_ioctl+0x3c0/0x4c0 net/ipv4/af_inet.c:1001
 sock_do_ioctl+0xdc/0x300 net/socket.c:1238
 sock_ioctl+0x576/0x790 net/socket.c:1359
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:598 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:584
 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: 0033:0x7f9b85bc0378
Code: 00 00 48 8d 44 24 08 48 89 54 24 e0 48 89 44 24 c0 48 8d 44 24 d0 48 89 44 24 c8 b8 10 00 00 00 c7 44 24 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 07 89 d0 c3 0f 1f 40 00 48 8b 15 49 3a 0d
RSP: 002b:00007ffdd9c500b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000019 RCX: 00007f9b85bc0378
RDX: 00007ffdd9c602b0 RSI: 0000000000008914 RDI: 0000000000000019
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffdd9c70450
R13: 00007f9b85ac06c8 R14: 0000000000000028 R15: 0000000000008914
 </TASK>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/08/14 06:19 upstream 91325f31afc1 22ec1469 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root possible deadlock in xsk_notifier
2025/08/07 14:49 upstream 6e64f4580381 04cffc22 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root possible deadlock in xsk_notifier
2025/06/24 18:14 upstream 78f4e737a53e 26d77996 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root possible deadlock in xsk_notifier
* Struck through repros no longer work on HEAD.