====================================================== WARNING: possible circular locking dependency detected 4.18.0-rc3+ #32 Not tainted ------------------------------------------------------ syz-executor4/21629 is trying to acquire lock: 00000000c8b507d2 (&(&u->lock)->rlock/1){+.+.}, at: sk_diag_dump_icons net/unix/diag.c:82 [inline] 00000000c8b507d2 (&(&u->lock)->rlock/1){+.+.}, at: sk_diag_fill.isra.5+0xa57/0x10f0 net/unix/diag.c:144 but task is already holding lock: 00000000a8a09175 (rlock-AF_UNIX){+.+.}, at: spin_lock include/linux/spinlock.h:310 [inline] 00000000a8a09175 (rlock-AF_UNIX){+.+.}, at: sk_diag_dump_icons net/unix/diag.c:64 [inline] 00000000a8a09175 (rlock-AF_UNIX){+.+.}, at: sk_diag_fill.isra.5+0x962/0x10f0 net/unix/diag.c:144 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: IPv6: ADDRCONF(NETDEV_CHANGE): vcan0: link becomes ready -> #1 (rlock-AF_UNIX){+.+.}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x96/0xc0 kernel/locking/spinlock.c:152 skb_queue_tail+0x26/0x150 net/core/skbuff.c:2915 unix_dgram_sendmsg+0xfa2/0x1750 net/unix/af_unix.c:1797 sock_sendmsg_nosec net/socket.c:641 [inline] sock_sendmsg+0xd5/0x120 net/socket.c:651 ___sys_sendmsg+0x51d/0x930 net/socket.c:2125 __sys_sendmmsg+0x3bb/0x6f0 net/socket.c:2213 __compat_sys_sendmmsg net/compat.c:770 [inline] __do_compat_sys_sendmmsg net/compat.c:777 [inline] __se_compat_sys_sendmmsg net/compat.c:774 [inline] __ia32_compat_sys_sendmmsg+0x9f/0x100 net/compat.c:774 do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline] do_fast_syscall_32+0x34d/0xfb2 arch/x86/entry/common.c:397 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139 -> #0 (&(&u->lock)->rlock/1){+.+.}: lock_acquire+0x1e4/0x540 kernel/locking/lockdep.c:3924 _raw_spin_lock_nested+0x28/0x40 kernel/locking/spinlock.c:354 sk_diag_dump_icons net/unix/diag.c:82 [inline] sk_diag_fill.isra.5+0xa57/0x10f0 net/unix/diag.c:144 sk_diag_dump net/unix/diag.c:178 [inline] unix_diag_dump+0x35f/0x550 net/unix/diag.c:206 netlink_dump+0x519/0xd50 net/netlink/af_netlink.c:2226 __netlink_dump_start+0x51a/0x780 net/netlink/af_netlink.c:2323 netlink_dump_start include/linux/netlink.h:214 [inline] unix_diag_handler_dump+0x3fc/0x7d0 net/unix/diag.c:307 __sock_diag_cmd net/core/sock_diag.c:230 [inline] sock_diag_rcv_msg+0x2e0/0x3d0 net/core/sock_diag.c:261 netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2448 sock_diag_rcv+0x2a/0x40 net/core/sock_diag.c:272 netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline] netlink_unicast+0x5a0/0x760 net/netlink/af_netlink.c:1336 netlink_sendmsg+0xa18/0xfd0 net/netlink/af_netlink.c:1901 sock_sendmsg_nosec net/socket.c:641 [inline] sock_sendmsg+0xd5/0x120 net/socket.c:651 sock_write_iter+0x362/0x5c0 net/socket.c:920 call_write_iter include/linux/fs.h:1793 [inline] do_iter_readv_writev+0x897/0xa90 fs/read_write.c:680 do_iter_write+0x185/0x5f0 fs/read_write.c:959 compat_writev+0x234/0x420 fs/read_write.c:1273 do_compat_writev+0x128/0x260 fs/read_write.c:1294 __do_compat_sys_writev fs/read_write.c:1305 [inline] __se_compat_sys_writev fs/read_write.c:1301 [inline] __ia32_compat_sys_writev+0x74/0xb0 fs/read_write.c:1301 do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline] do_fast_syscall_32+0x34d/0xfb2 arch/x86/entry/common.c:397 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(rlock-AF_UNIX); lock(&(&u->lock)->rlock/1); lock(rlock-AF_UNIX); lock(&(&u->lock)->rlock/1); *** DEADLOCK *** 5 locks held by syz-executor4/21629: #0: 0000000033244bc7 (sock_diag_mutex){+.+.}, at: sock_diag_rcv+0x1b/0x40 net/core/sock_diag.c:271 #1: 000000006c9cfab7 (sock_diag_table_mutex){+.+.}, at: __sock_diag_cmd net/core/sock_diag.c:225 [inline] #1: 000000006c9cfab7 (sock_diag_table_mutex){+.+.}, at: sock_diag_rcv_msg+0x169/0x3d0 net/core/sock_diag.c:261 #2: 00000000fb314386 (nlk_cb_mutex-SOCK_DIAG){+.+.}, at: netlink_dump+0x9f/0xd50 net/netlink/af_netlink.c:2182 #3: 0000000098c4a67b (unix_table_lock){+.+.}, at: spin_lock include/linux/spinlock.h:310 [inline] #3: 0000000098c4a67b (unix_table_lock){+.+.}, at: unix_diag_dump+0x10a/0x550 net/unix/diag.c:192 #4: 00000000a8a09175 (rlock-AF_UNIX){+.+.}, at: spin_lock include/linux/spinlock.h:310 [inline] #4: 00000000a8a09175 (rlock-AF_UNIX){+.+.}, at: sk_diag_dump_icons net/unix/diag.c:64 [inline] #4: 00000000a8a09175 (rlock-AF_UNIX){+.+.}, at: sk_diag_fill.isra.5+0x962/0x10f0 net/unix/diag.c:144 stack backtrace: CPU: 1 PID: 21629 Comm: syz-executor4 Not tainted 4.18.0-rc3+ #32 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113 print_circular_bug.isra.36.cold.57+0x1bd/0x27d kernel/locking/lockdep.c:1227 check_prev_add kernel/locking/lockdep.c:1867 [inline] check_prevs_add kernel/locking/lockdep.c:1980 [inline] validate_chain kernel/locking/lockdep.c:2421 [inline] __lock_acquire+0x3449/0x5020 kernel/locking/lockdep.c:3435 lock_acquire+0x1e4/0x540 kernel/locking/lockdep.c:3924 _raw_spin_lock_nested+0x28/0x40 kernel/locking/spinlock.c:354 sk_diag_dump_icons net/unix/diag.c:82 [inline] sk_diag_fill.isra.5+0xa57/0x10f0 net/unix/diag.c:144 sk_diag_dump net/unix/diag.c:178 [inline] unix_diag_dump+0x35f/0x550 net/unix/diag.c:206 netlink_dump+0x519/0xd50 net/netlink/af_netlink.c:2226 __netlink_dump_start+0x51a/0x780 net/netlink/af_netlink.c:2323 netlink_dump_start include/linux/netlink.h:214 [inline] unix_diag_handler_dump+0x3fc/0x7d0 net/unix/diag.c:307 __sock_diag_cmd net/core/sock_diag.c:230 [inline] sock_diag_rcv_msg+0x2e0/0x3d0 net/core/sock_diag.c:261 netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2448 sock_diag_rcv+0x2a/0x40 net/core/sock_diag.c:272 netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline] netlink_unicast+0x5a0/0x760 net/netlink/af_netlink.c:1336 netlink_sendmsg+0xa18/0xfd0 net/netlink/af_netlink.c:1901 sock_sendmsg_nosec net/socket.c:641 [inline] sock_sendmsg+0xd5/0x120 net/socket.c:651 sock_write_iter+0x362/0x5c0 net/socket.c:920 call_write_iter include/linux/fs.h:1793 [inline] do_iter_readv_writev+0x897/0xa90 fs/read_write.c:680 do_iter_write+0x185/0x5f0 fs/read_write.c:959 compat_writev+0x234/0x420 fs/read_write.c:1273 do_compat_writev+0x128/0x260 fs/read_write.c:1294 __do_compat_sys_writev fs/read_write.c:1305 [inline] __se_compat_sys_writev fs/read_write.c:1301 [inline] __ia32_compat_sys_writev+0x74/0xb0 fs/read_write.c:1301 do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline] do_fast_syscall_32+0x34d/0xfb2 arch/x86/entry/common.c:397 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139 RIP: 0023:0xf7f6ccb9 Code: 55 08 8b 88 64 cd ff ff 8b 98 68 cd ff ff 89 c8 85 d2 74 02 89 0a 5b 5d c3 8b 04 24 c3 8b 1c 24 c3 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90 RSP: 002b:00000000f5f680ac EFLAGS: 00000282 ORIG_RAX: 0000000000000092 RAX: ffffffffffffffda RBX: 0000000000000016 RCX: 00000000200000c0 RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 IPv6: ADDRCONF(NETDEV_CHANGE): vcan0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): vcan0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): vcan0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): vcan0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): vcan0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): lo: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): vcan0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): vcan0: link becomes ready sctp: [Deprecated]: syz-executor2 (pid 21898) Use of int in max_burst socket option deprecated. Use struct sctp_assoc_value instead IPv6: ADDRCONF(NETDEV_CHANGE): vcan0: link becomes ready sctp: [Deprecated]: syz-executor2 (pid 21910) Use of int in max_burst socket option deprecated. Use struct sctp_assoc_value instead IPv6: ADDRCONF(NETDEV_CHANGE): vcan0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): vcan0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): vcan0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): vcan0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): vcan0: link becomes ready