====================================================== WARNING: possible circular locking dependency detected 4.17.0+ #84 Not tainted ------------------------------------------------------ syz-executor0/23381 is trying to acquire lock: 00000000981fea1c (&(&u->lock)->rlock/1){+.+.}, at: sk_diag_dump_icons net/unix/diag.c:82 [inline] 00000000981fea1c (&(&u->lock)->rlock/1){+.+.}, at: sk_diag_fill.isra.5+0xa43/0x10d0 net/unix/diag.c:144 but task is already holding lock: 00000000472067f9 (rlock-AF_UNIX){+.+.}, at: spin_lock include/linux/spinlock.h:310 [inline] 00000000472067f9 (rlock-AF_UNIX){+.+.}, at: sk_diag_dump_icons net/unix/diag.c:64 [inline] 00000000472067f9 (rlock-AF_UNIX){+.+.}, at: sk_diag_fill.isra.5+0x94e/0x10d0 net/unix/diag.c:144 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #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+0xf77/0x1730 net/unix/af_unix.c:1796 sock_sendmsg_nosec net/socket.c:645 [inline] sock_sendmsg+0xd5/0x120 net/socket.c:655 ___sys_sendmsg+0x525/0x940 net/socket.c:2161 __sys_sendmmsg+0x240/0x6f0 net/socket.c:2256 __do_sys_sendmmsg net/socket.c:2285 [inline] __se_sys_sendmmsg net/socket.c:2282 [inline] __x64_sys_sendmmsg+0x9d/0x100 net/socket.c:2282 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&(&u->lock)->rlock/1){+.+.}: lock_acquire+0x1dc/0x520 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+0xa43/0x10d0 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+0x507/0xd20 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+0x3f4/0x7b0 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+0x58b/0x740 net/netlink/af_netlink.c:1336 netlink_sendmsg+0x9f0/0xfa0 net/netlink/af_netlink.c:1901 sock_sendmsg_nosec net/socket.c:645 [inline] sock_sendmsg+0xd5/0x120 net/socket.c:655 sock_write_iter+0x35a/0x5a0 net/socket.c:924 call_write_iter include/linux/fs.h:1793 [inline] do_iter_readv_writev+0x87d/0xa70 fs/read_write.c:680 do_iter_write+0x185/0x5f0 fs/read_write.c:959 vfs_writev+0x1c7/0x330 fs/read_write.c:1004 do_writev+0x112/0x2f0 fs/read_write.c:1039 __do_sys_writev fs/read_write.c:1112 [inline] __se_sys_writev fs/read_write.c:1109 [inline] __x64_sys_writev+0x75/0xb0 fs/read_write.c:1109 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe 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-executor0/23381: #0: 00000000e384712d (sock_diag_mutex){+.+.}, at: sock_diag_rcv+0x1b/0x40 net/core/sock_diag.c:271 #1: 00000000832c80d1 (sock_diag_table_mutex){+.+.}, at: __sock_diag_cmd net/core/sock_diag.c:225 [inline] #1: 00000000832c80d1 (sock_diag_table_mutex){+.+.}, at: sock_diag_rcv_msg+0x169/0x3d0 net/core/sock_diag.c:261 #2: 000000005196c5b8 (nlk_cb_mutex-SOCK_DIAG){+.+.}, at: netlink_dump+0x98/0xd20 net/netlink/af_netlink.c:2182 #3: 000000009c6605e1 (unix_table_lock){+.+.}, at: spin_lock include/linux/spinlock.h:310 [inline] #3: 000000009c6605e1 (unix_table_lock){+.+.}, at: unix_diag_dump+0x10a/0x550 net/unix/diag.c:192 #4: 00000000472067f9 (rlock-AF_UNIX){+.+.}, at: spin_lock include/linux/spinlock.h:310 [inline] #4: 00000000472067f9 (rlock-AF_UNIX){+.+.}, at: sk_diag_dump_icons net/unix/diag.c:64 [inline] #4: 00000000472067f9 (rlock-AF_UNIX){+.+.}, at: sk_diag_fill.isra.5+0x94e/0x10d0 net/unix/diag.c:144 stack backtrace: CPU: 1 PID: 23381 Comm: syz-executor0 Not tainted 4.17.0+ #84 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+0x1b9/0x294 lib/dump_stack.c:113 print_circular_bug.isra.36.cold.56+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+0x343e/0x5140 kernel/locking/lockdep.c:3435 lock_acquire+0x1dc/0x520 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+0xa43/0x10d0 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+0x507/0xd20 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+0x3f4/0x7b0 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+0x58b/0x740 net/netlink/af_netlink.c:1336 netlink_sendmsg+0x9f0/0xfa0 net/netlink/af_netlink.c:1901 sock_sendmsg_nosec net/socket.c:645 [inline] sock_sendmsg+0xd5/0x120 net/socket.c:655 sock_write_iter+0x35a/0x5a0 net/socket.c:924 call_write_iter include/linux/fs.h:1793 [inline] do_iter_readv_writev+0x87d/0xa70 fs/read_write.c:680 do_iter_write+0x185/0x5f0 fs/read_write.c:959 vfs_writev+0x1c7/0x330 fs/read_write.c:1004 do_writev+0x112/0x2f0 fs/read_write.c:1039 __do_sys_writev fs/read_write.c:1112 [inline] __se_sys_writev fs/read_write.c:1109 [inline] __x64_sys_writev+0x75/0xb0 fs/read_write.c:1109 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x455b29 Code: 1d ba fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 eb b9 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f661e155c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000014 RAX: ffffffffffffffda RBX: 00007f661e1566d4 RCX: 0000000000455b29 RDX: 0000000000000001 RSI: 00000000200000c0 RDI: 0000000000000016 RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000004c06bc R14: 00000000004d37f8 R15: 0000000000000000