====================================================== WARNING: possible circular locking dependency detected 6.3.0-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.4/27739 is trying to acquire lock: ffff888077b521e8 (rlock-AF_UNIX){+.+.}-{2:2}, at: skb_queue_tail+0x36/0x120 net/core/skbuff.c:3683 but task is already holding lock: ffff888077b52680 (&u->lock/1){+.+.}-{2:2}, at: unix_dgram_sendmsg+0xefe/0x2050 net/unix/af_unix.c:2059 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&u->lock/1){+.+.}-{2:2}: lock_acquire+0x1e1/0x520 kernel/locking/lockdep.c:5669 _raw_spin_lock_nested+0x31/0x40 kernel/locking/spinlock.c:378 sk_diag_dump_icons net/unix/diag.c:87 [inline] sk_diag_fill+0x6ea/0xfe0 net/unix/diag.c:157 sk_diag_dump net/unix/diag.c:196 [inline] unix_diag_dump+0x3eb/0x640 net/unix/diag.c:220 netlink_dump+0x656/0xcc0 net/netlink/af_netlink.c:2299 __netlink_dump_start+0x536/0x700 net/netlink/af_netlink.c:2404 netlink_dump_start include/linux/netlink.h:308 [inline] unix_diag_handler_dump+0x1c0/0x8e0 net/unix/diag.c:319 sock_diag_rcv_msg+0xe3/0x400 netlink_rcv_skb+0x1df/0x430 net/netlink/af_netlink.c:2577 sock_diag_rcv+0x2a/0x40 net/core/sock_diag.c:280 netlink_unicast_kernel net/netlink/af_netlink.c:1339 [inline] netlink_unicast+0x7c3/0x990 net/netlink/af_netlink.c:1365 netlink_sendmsg+0xa2a/0xd60 net/netlink/af_netlink.c:1942 sock_sendmsg_nosec net/socket.c:724 [inline] sock_sendmsg net/socket.c:747 [inline] sock_write_iter+0x397/0x520 net/socket.c:1138 do_iter_write+0x6ea/0xc50 fs/read_write.c:861 vfs_writev fs/read_write.c:934 [inline] do_writev+0x27f/0x470 fs/read_write.c:977 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd -> #0 (rlock-AF_UNIX){+.+.}-{2:2}: check_prev_add kernel/locking/lockdep.c:3098 [inline] check_prevs_add kernel/locking/lockdep.c:3217 [inline] validate_chain+0x166b/0x58e0 kernel/locking/lockdep.c:3832 __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056 lock_acquire+0x1e1/0x520 kernel/locking/lockdep.c:5669 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162 skb_queue_tail+0x36/0x120 net/core/skbuff.c:3683 unix_dgram_sendmsg+0x1502/0x2050 net/unix/af_unix.c:2082 sock_sendmsg_nosec net/socket.c:724 [inline] sock_sendmsg net/socket.c:747 [inline] ____sys_sendmsg+0x58f/0x890 net/socket.c:2501 ___sys_sendmsg net/socket.c:2555 [inline] __sys_sendmmsg+0x3af/0x730 net/socket.c:2641 __do_sys_sendmmsg net/socket.c:2670 [inline] __se_sys_sendmmsg net/socket.c:2667 [inline] __x64_sys_sendmmsg+0xa0/0xb0 net/socket.c:2667 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 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(&u->lock/1); lock(rlock-AF_UNIX); lock(&u->lock/1); lock(rlock-AF_UNIX); *** DEADLOCK *** 1 lock held by syz-executor.4/27739: #0: ffff888077b52680 (&u->lock/1){+.+.}-{2:2}, at: unix_dgram_sendmsg+0xefe/0x2050 net/unix/af_unix.c:2059 stack backtrace: CPU: 1 PID: 27739 Comm: syz-executor.4 Not tainted 6.3.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/14/2023 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106 check_noncircular+0x2fe/0x3b0 kernel/locking/lockdep.c:2178 check_prev_add kernel/locking/lockdep.c:3098 [inline] check_prevs_add kernel/locking/lockdep.c:3217 [inline] validate_chain+0x166b/0x58e0 kernel/locking/lockdep.c:3832 __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056 lock_acquire+0x1e1/0x520 kernel/locking/lockdep.c:5669 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162 skb_queue_tail+0x36/0x120 net/core/skbuff.c:3683 unix_dgram_sendmsg+0x1502/0x2050 net/unix/af_unix.c:2082 sock_sendmsg_nosec net/socket.c:724 [inline] sock_sendmsg net/socket.c:747 [inline] ____sys_sendmsg+0x58f/0x890 net/socket.c:2501 ___sys_sendmsg net/socket.c:2555 [inline] __sys_sendmmsg+0x3af/0x730 net/socket.c:2641 __do_sys_sendmmsg net/socket.c:2670 [inline] __se_sys_sendmmsg net/socket.c:2667 [inline] __x64_sys_sendmmsg+0xa0/0xb0 net/socket.c:2667 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7f6d5108c169 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:00007f6d51e01168 EFLAGS: 00000246 ORIG_RAX: 0000000000000133 RAX: ffffffffffffffda RBX: 00007f6d511ac120 RCX: 00007f6d5108c169 RDX: 0000000000000001 RSI: 0000000020002180 RDI: 0000000000000004 RBP: 00007f6d510e7ca1 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000020004050 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fff59b4654f R14: 00007f6d51e01300 R15: 0000000000022000