Subject: [syzbot] [bpf?] [net?] possible deadlock in xsk_bind

From: syzbot <[email-masked]>
Date: Wed, 09 Apr 2025 19:35:25 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    61f96e684edd Merge tag 'net-6.15-rc1' of git://git.kernel...
git tree:       net
console output: https://syzkaller.appspot.com/x/log.txt?x=1635523f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f2054704dd53fb80
dashboard link: https://syzkaller.appspot.com/bug?extid=46043677477d6064a1a0
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a3119b4324e8/disk-61f96e68.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ee1ca254d083/vmlinux-61f96e68.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ed04807ee582/bzImage-61f96e68.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

======================================================
WARNING: possible circular locking dependency detected
6.14.0-syzkaller-13305-g61f96e684edd #0 Not tainted
------------------------------------------------------
syz.0.1422/11074 is trying to acquire lock:
ffff888035a5cd30 (&dev_instance_lock_key#3){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2751 [inline]
ffff888035a5cd30 (&dev_instance_lock_key#3){+.+.}-{4:4}, at: netdev_lock_ops include/net/netdev_lock.h:42 [inline]
ffff888035a5cd30 (&dev_instance_lock_key#3){+.+.}-{4:4}, at: xsk_bind+0x2fd/0xfb0 net/xdp/xsk.c:1188

but task is already holding lock:
ffff88805421d6f0 (&xs->mutex){+.+.}-{4:4}, at: xsk_bind+0x166/0xfb0 net/xdp/xsk.c:1176

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #3 (&xs->mutex){+.+.}-{4:4}:
       lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x1a5/0x10c0 kernel/locking/mutex.c:746
       xsk_notifier+0xcf/0x230 net/xdp/xsk.c:1648
       notifier_call_chain+0x1a5/0x3f0 kernel/notifier.c:85
       call_netdevice_notifiers_extack net/core/dev.c:2221 [inline]
       call_netdevice_notifiers net/core/dev.c:2235 [inline]
       unregister_netdevice_many_notify+0x1572/0x2510 net/core/dev.c:11980
       unregister_netdevice_many net/core/dev.c:12044 [inline]
       unregister_netdevice_queue+0x383/0x400 net/core/dev.c:11896
       unregister_netdevice include/linux/netdevice.h:3374 [inline]
       ip6_tnl_siocdevprivate+0x552/0x1570 net/ipv6/ip6_tunnel.c:1717
       dev_siocdevprivate net/core/dev_ioctl.c:521 [inline]
       dev_ifsioc+0xc04/0x1010 net/core/dev_ioctl.c:631
       dev_ioctl+0x8c3/0x1380 net/core/dev_ioctl.c:848
       sock_ioctl+0x819/0x900 net/socket.c:1236
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:906 [inline]
       __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:892
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&net->xdp.lock){+.+.}-{4:4}:
       lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x1a5/0x10c0 kernel/locking/mutex.c:746
       xsk_notifier+0x8b/0x230 net/xdp/xsk.c:1644
       notifier_call_chain+0x1a5/0x3f0 kernel/notifier.c:85
       call_netdevice_notifiers_extack net/core/dev.c:2221 [inline]
       call_netdevice_notifiers net/core/dev.c:2235 [inline]
       unregister_netdevice_many_notify+0x1572/0x2510 net/core/dev.c:11980
       unregister_netdevice_many net/core/dev.c:12044 [inline]
       unregister_netdevice_queue+0x383/0x400 net/core/dev.c:11896
       unregister_netdevice include/linux/netdevice.h:3374 [inline]
       _cfg80211_unregister_wdev+0x163/0x590 net/wireless/core.c:1256
       ieee80211_remove_interfaces+0x4f1/0x700 net/mac80211/iface.c:2316
       ieee80211_unregister_hw+0x5d/0x2c0 net/mac80211/main.c:1681
       mac80211_hwsim_del_radio+0x2c6/0x4c0 drivers/net/wireless/virtual/mac80211_hwsim.c:5665
       hwsim_exit_net+0x5c3/0x670 drivers/net/wireless/virtual/mac80211_hwsim.c:6545
       ops_exit_list net/core/net_namespace.c:172 [inline]
       cleanup_net+0x814/0xd60 net/core/net_namespace.c:654
       process_one_work kernel/workqueue.c:3238 [inline]
       process_scheduled_works+0xac3/0x18e0 kernel/workqueue.c:3319
       worker_thread+0x870/0xd50 kernel/workqueue.c:3400
       kthread+0x7b7/0x940 kernel/kthread.c:464
       ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (&rdev->wiphy.mtx){+.+.}-{4:4}:
       lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x1a5/0x10c0 kernel/locking/mutex.c:746
       class_wiphy_constructor include/net/cfg80211.h:6092 [inline]
       cfg80211_netdev_notifier_call+0x1b3/0x1430 net/wireless/core.c:1547
       notifier_call_chain+0x1a5/0x3f0 kernel/notifier.c:85
       call_netdevice_notifiers_extack net/core/dev.c:2221 [inline]
       call_netdevice_notifiers net/core/dev.c:2235 [inline]
       __dev_close_many+0x15d/0x760 net/core/dev.c:1680
       dev_close_many+0x250/0x4c0 net/core/dev.c:1734
       unregister_netdevice_many_notify+0x628/0x2510 net/core/dev.c:11949
       unregister_netdevice_many net/core/dev.c:12044 [inline]
       default_device_exit_batch+0x7ff/0x880 net/core/dev.c:12536
       ops_exit_list net/core/net_namespace.c:177 [inline]
       cleanup_net+0x8af/0xd60 net/core/net_namespace.c:654
       process_one_work kernel/workqueue.c:3238 [inline]
       process_scheduled_works+0xac3/0x18e0 kernel/workqueue.c:3319
       worker_thread+0x870/0xd50 kernel/workqueue.c:3400
       kthread+0x7b7/0x940 kernel/kthread.c:464
       ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #0 (&dev_instance_lock_key#3){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3166 [inline]
       check_prevs_add kernel/locking/lockdep.c:3285 [inline]
       validate_chain+0xa69/0x24e0 kernel/locking/lockdep.c:3909
       __lock_acquire+0xad5/0xd80 kernel/locking/lockdep.c:5235
       lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x1a5/0x10c0 kernel/locking/mutex.c:746
       netdev_lock include/linux/netdevice.h:2751 [inline]
       netdev_lock_ops include/net/netdev_lock.h:42 [inline]
       xsk_bind+0x2fd/0xfb0 net/xdp/xsk.c:1188
       __sys_bind_socket net/socket.c:1810 [inline]
       __sys_bind+0x1de/0x290 net/socket.c:1841
       __do_sys_bind net/socket.c:1846 [inline]
       __se_sys_bind net/socket.c:1844 [inline]
       __x64_sys_bind+0x7a/0x90 net/socket.c:1844
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf3/0x230 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:
  &dev_instance_lock_key#3 --> &net->xdp.lock --> &xs->mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&xs->mutex);
                               lock(&net->xdp.lock);
                               lock(&xs->mutex);
  lock(&dev_instance_lock_key#3);

 *** DEADLOCK ***

2 locks held by syz.0.1422/11074:
 #0: ffffffff900fc9c8 (rtnl_mutex){+.+.}-{4:4}, at: xsk_bind+0x153/0xfb0 net/xdp/xsk.c:1175
 #1: ffff88805421d6f0 (&xs->mutex){+.+.}-{4:4}, at: xsk_bind+0x166/0xfb0 net/xdp/xsk.c:1176

stack backtrace:
CPU: 1 UID: 0 PID: 11074 Comm: syz.0.1422 Not tainted 6.14.0-syzkaller-13305-g61f96e684edd #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2079
 check_noncircular+0x142/0x160 kernel/locking/lockdep.c:2211
 check_prev_add kernel/locking/lockdep.c:3166 [inline]
 check_prevs_add kernel/locking/lockdep.c:3285 [inline]
 validate_chain+0xa69/0x24e0 kernel/locking/lockdep.c:3909
 __lock_acquire+0xad5/0xd80 kernel/locking/lockdep.c:5235
 lock_acquire+0x116/0x2f0 kernel/locking/lockdep.c:5866
 __mutex_lock_common kernel/locking/mutex.c:601 [inline]
 __mutex_lock+0x1a5/0x10c0 kernel/locking/mutex.c:746
 netdev_lock include/linux/netdevice.h:2751 [inline]
 netdev_lock_ops include/net/netdev_lock.h:42 [inline]
 xsk_bind+0x2fd/0xfb0 net/xdp/xsk.c:1188
 __sys_bind_socket net/socket.c:1810 [inline]
 __sys_bind+0x1de/0x290 net/socket.c:1841
 __do_sys_bind net/socket.c:1846 [inline]
 __se_sys_bind net/socket.c:1844 [inline]
 __x64_sys_bind+0x7a/0x90 net/socket.c:1844
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd38178d169
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:00007fd37f5f6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000031
RAX: ffffffffffffffda RBX: 00007fd3819a5fa0 RCX: 00007fd38178d169
RDX: 0000000000000010 RSI: 0000200000000180 RDI: 0000000000000003
RBP: 00007fd38180e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fd3819a5fa0 R15: 00007ffc59db1d08
 </TASK>

---
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