====================================================== WARNING: possible circular locking dependency detected 4.16.0-rc6+ #290 Not tainted ------------------------------------------------------ syz-executor7/20971 is trying to acquire lock: (&af_unix_sk_receive_queue_lock_key){+.+.}, at: [<00000000271ef0d8>] skb_queue_tail+0x26/0x150 net/core/skbuff.c:2899 but task is already holding lock: (&(&u->lock)->rlock/1){+.+.}, at: [<000000004e725e14>] unix_state_double_lock+0x7b/0xb0 net/unix/af_unix.c:1088 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&(&u->lock)->rlock/1){+.+.}: _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.4+0xa52/0xfe0 net/unix/diag.c:144 sk_diag_dump net/unix/diag.c:178 [inline] unix_diag_dump+0x400/0x4f0 net/unix/diag.c:206 netlink_dump+0x492/0xcf0 net/netlink/af_netlink.c:2221 __netlink_dump_start+0x4ec/0x710 net/netlink/af_netlink.c:2318 netlink_dump_start include/linux/netlink.h:214 [inline] unix_diag_handler_dump+0x3e7/0x750 net/unix/diag.c:307 __sock_diag_cmd net/core/sock_diag.c:230 [inline] sock_diag_rcv_msg+0x204/0x360 net/core/sock_diag.c:261 netlink_rcv_skb+0x14b/0x380 net/netlink/af_netlink.c:2443 sock_diag_rcv+0x2a/0x40 net/core/sock_diag.c:272 netlink_unicast_kernel net/netlink/af_netlink.c:1307 [inline] netlink_unicast+0x4c4/0x6b0 net/netlink/af_netlink.c:1333 netlink_sendmsg+0xa4a/0xe80 net/netlink/af_netlink.c:1896 sock_sendmsg_nosec net/socket.c:629 [inline] sock_sendmsg+0xca/0x110 net/socket.c:639 sock_write_iter+0x31a/0x5d0 net/socket.c:908 call_write_iter include/linux/fs.h:1782 [inline] new_sync_write fs/read_write.c:469 [inline] __vfs_write+0x684/0x970 fs/read_write.c:482 vfs_write+0x189/0x510 fs/read_write.c:544 SYSC_write fs/read_write.c:589 [inline] SyS_write+0xef/0x220 fs/read_write.c:581 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7 -> #0 (&af_unix_sk_receive_queue_lock_key){+.+.}: lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920 __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:2899 unix_dgram_sendmsg+0xa30/0x1610 net/unix/af_unix.c:1807 sock_sendmsg_nosec net/socket.c:629 [inline] sock_sendmsg+0xca/0x110 net/socket.c:639 ___sys_sendmsg+0x320/0x8b0 net/socket.c:2047 __sys_sendmmsg+0x1ee/0x620 net/socket.c:2137 SYSC_sendmmsg net/socket.c:2168 [inline] SyS_sendmmsg+0x35/0x60 net/socket.c:2163 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&(&u->lock)->rlock/1); lock(&af_unix_sk_receive_queue_lock_key); lock(&(&u->lock)->rlock/1); lock(&af_unix_sk_receive_queue_lock_key); *** DEADLOCK *** 1 lock held by syz-executor7/20971: #0: (&(&u->lock)->rlock/1){+.+.}, at: [<000000004e725e14>] unix_state_double_lock+0x7b/0xb0 net/unix/af_unix.c:1088 stack backtrace: CPU: 0 PID: 20971 Comm: syz-executor7 Not tainted 4.16.0-rc6+ #290 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x24d lib/dump_stack.c:53 print_circular_bug.isra.38+0x2cd/0x2dc kernel/locking/lockdep.c:1223 check_prev_add kernel/locking/lockdep.c:1863 [inline] check_prevs_add kernel/locking/lockdep.c:1976 [inline] validate_chain kernel/locking/lockdep.c:2417 [inline] __lock_acquire+0x30a8/0x3e00 kernel/locking/lockdep.c:3431 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920 __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:2899 unix_dgram_sendmsg+0xa30/0x1610 net/unix/af_unix.c:1807 sock_sendmsg_nosec net/socket.c:629 [inline] sock_sendmsg+0xca/0x110 net/socket.c:639 ___sys_sendmsg+0x320/0x8b0 net/socket.c:2047 __sys_sendmmsg+0x1ee/0x620 net/socket.c:2137 SYSC_sendmmsg net/socket.c:2168 [inline] SyS_sendmmsg+0x35/0x60 net/socket.c:2163 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x455269 RSP: 002b:00007f71ffad6c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000133 RAX: ffffffffffffffda RBX: 00007f71ffad76d4 RCX: 0000000000455269 RDX: 04924924924924f4 RSI: 0000000020000200 RDI: 0000000000000016 RBP: 000000000072bf58 R08: 0000000000000000 R09: 0000000000000000 R10: 00000000200000d4 R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000000004ca R14: 00000000006f9390 R15: 0000000000000001 IPVS: Unknown mcast interface: bcsh0 IPVS: Unknown mcast interface: bcsh0 IPVS: Unknown mcast interface: bcsh0 IPVS: Unknown mcast interface: bcsh0 IPVS: Unknown mcast interface: bcsh0 IPVS: Unknown mcast interface: bcsh0 IPVS: Unknown mcast interface: bcsh0 IPVS: Unknown mcast interface: bcsh0 IPVS: Unknown mcast interface: bcsh0 IPVS: sync thread started: state = BACKUP, mcast_ifn = bcsh0, syncid = 0, id = 0 IPVS: Unknown mcast interface: bcsh0 IPVS: Unknown mcast interface: bcsh0 IPVS: Unknown mcast interface: bcsh0 IPVS: Unknown mcast interface: bcsh0 IPVS: Unknown mcast interface: bcsh0 IPVS: Unknown mcast interface: bcsh0 IPVS: Unknown mcast interface: bcsh0 IPVS: Unknown mcast interface: bcsh0