====================================================== WARNING: possible circular locking dependency detected 6.2.0-rc4-next-20230117-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.2/26821 is trying to acquire lock: ffff888043a140b0 (slock-AF_INET6){+.-.}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:355 [inline] ffff888043a140b0 (slock-AF_INET6){+.-.}-{2:2}, at: release_sock+0x1f/0x1b0 net/core/sock.c:3483 but task is already holding lock: ffff888043a143b8 (clock-AF_INET6){++--}-{2:2}, at: l2tp_tunnel_register+0x1c3/0xd80 net/l2tp/l2tp_core.c:1484 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (clock-AF_INET6){++--}-{2:2}: __raw_write_lock_bh include/linux/rwlock_api_smp.h:202 [inline] _raw_write_lock_bh+0x33/0x40 kernel/locking/spinlock.c:334 sock_orphan include/net/sock.h:2094 [inline] inet_child_forget+0x73/0x2d0 net/ipv4/inet_connection_sock.c:1258 inet_csk_listen_stop+0x235/0x1110 net/ipv4/inet_connection_sock.c:1399 dccp_close+0xa2f/0xd60 net/dccp/proto.c:993 inet_release+0x132/0x270 net/ipv4/af_inet.c:428 inet6_release+0x50/0x70 net/ipv6/af_inet6.c:489 __sock_release+0xcd/0x280 net/socket.c:651 sock_close+0x1c/0x20 net/socket.c:1390 __fput+0x27c/0xa90 fs/file_table.c:321 task_work_run+0x16f/0x270 kernel/task_work.c:179 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] exit_to_user_mode_loop kernel/entry/common.c:171 [inline] exit_to_user_mode_prepare+0x210/0x240 kernel/entry/common.c:204 __syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline] syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:297 do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x63/0xcd -> #0 (slock-AF_INET6){+.-.}-{2:2}: check_prev_add kernel/locking/lockdep.c:3107 [inline] check_prevs_add kernel/locking/lockdep.c:3226 [inline] validate_chain kernel/locking/lockdep.c:3841 [inline] __lock_acquire+0x2a9d/0x5780 kernel/locking/lockdep.c:5073 lock_acquire.part.0+0x11c/0x350 kernel/locking/lockdep.c:5690 __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:355 [inline] release_sock+0x1f/0x1b0 net/core/sock.c:3483 l2tp_tunnel_register+0x2e0/0xd80 net/l2tp/l2tp_core.c:1487 pppol2tp_connect+0xcdc/0x1a80 net/l2tp/l2tp_ppp.c:723 __sys_connect_file+0x153/0x1a0 net/socket.c:2001 __sys_connect+0x165/0x1a0 net/socket.c:2018 __do_sys_connect net/socket.c:2028 [inline] __se_sys_connect net/socket.c:2025 [inline] __x64_sys_connect+0x73/0xb0 net/socket.c:2025 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(clock-AF_INET6); lock(slock-AF_INET6); lock(clock-AF_INET6); lock(slock-AF_INET6); *** DEADLOCK *** 3 locks held by syz-executor.2/26821: #0: ffff888043838130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1725 [inline] #0: ffff888043838130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: pppol2tp_connect+0xadc/0x1a80 net/l2tp/l2tp_ppp.c:675 #1: ffff888043a14130 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1725 [inline] #1: ffff888043a14130 (sk_lock-AF_INET6){+.+.}-{0:0}, at: l2tp_tunnel_register+0x1af/0xd80 net/l2tp/l2tp_core.c:1483 #2: ffff888043a143b8 (clock-AF_INET6){++--}-{2:2}, at: l2tp_tunnel_register+0x1c3/0xd80 net/l2tp/l2tp_core.c:1484 stack backtrace: CPU: 1 PID: 26821 Comm: syz-executor.2 Not tainted 6.2.0-rc4-next-20230117-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2187 check_prev_add kernel/locking/lockdep.c:3107 [inline] check_prevs_add kernel/locking/lockdep.c:3226 [inline] validate_chain kernel/locking/lockdep.c:3841 [inline] __lock_acquire+0x2a9d/0x5780 kernel/locking/lockdep.c:5073 lock_acquire.part.0+0x11c/0x350 kernel/locking/lockdep.c:5690 __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:355 [inline] release_sock+0x1f/0x1b0 net/core/sock.c:3483 l2tp_tunnel_register+0x2e0/0xd80 net/l2tp/l2tp_core.c:1487 pppol2tp_connect+0xcdc/0x1a80 net/l2tp/l2tp_ppp.c:723 __sys_connect_file+0x153/0x1a0 net/socket.c:2001 __sys_connect+0x165/0x1a0 net/socket.c:2018 __do_sys_connect net/socket.c:2028 [inline] __se_sys_connect net/socket.c:2025 [inline] __x64_sys_connect+0x73/0xb0 net/socket.c:2025 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7f201888c0c9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f2019654168 EFLAGS: 00000246 ORIG_RAX: 000000000000002a RAX: ffffffffffffffda RBX: 00007f20189abf80 RCX: 00007f201888c0c9 RDX: 0000000000000032 RSI: 0000000020000240 RDI: 0000000000000003 RBP: 00007f20188e7ae9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fffe320879f R14: 00007f2019654300 R15: 0000000000022000