======================================================
[ INFO: possible circular locking dependency detected ]
4.4.174+ #17 Not tainted
-------------------------------------------------------
syz-executor.3/14002 is trying to acquire lock:
 (&(&q->lock)->rlock){+.-...}, at: [<ffffffff823ba312>] spin_lock include/linux/spinlock.h:302 [inline]
 (&(&q->lock)->rlock){+.-...}, at: [<ffffffff823ba312>] ip_defrag+0x322/0x3b70 net/ipv4/ip_fragment.c:690

but task is already holding lock:
 (_xmit_NETROM){+.-...}, at: [<ffffffff822b1b58>] spin_lock include/linux/spinlock.h:302 [inline]
 (_xmit_NETROM){+.-...}, at: [<ffffffff822b1b58>] __netif_tx_lock include/linux/netdevice.h:3306 [inline]
 (_xmit_NETROM){+.-...}, at: [<ffffffff822b1b58>] sch_direct_xmit+0x238/0x700 net/sched/sch_generic.c:163

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

       [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82717c98>] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline]
       [<ffffffff82717c98>] _raw_spin_lock+0x38/0x50 kernel/locking/spinlock.c:151
       [<ffffffff814d0d32>] spin_lock include/linux/spinlock.h:302 [inline]
       [<ffffffff814d0d32>] fasync_insert_entry+0x32/0x2b0 fs/fcntl.c:631
       [<ffffffff814d100b>] fasync_add_entry fs/fcntl.c:676 [inline]
       [<ffffffff814d100b>] fasync_helper+0x5b/0xb0 fs/fcntl.c:694
       [<ffffffff821d34a1>] sock_fasync+0xd1/0x200 net/socket.c:1076
       [<ffffffff814cf9d9>] setfl fs/fcntl.c:69 [inline]
       [<ffffffff814cf9d9>] do_fcntl fs/fcntl.c:270 [inline]
       [<ffffffff814cf9d9>] SYSC_fcntl fs/fcntl.c:375 [inline]
       [<ffffffff814cf9d9>] SyS_fcntl+0x4e9/0xb10 fs/fcntl.c:360
       [<ffffffff81597876>] C_SYSC_fcntl64 fs/compat.c:483 [inline]
       [<ffffffff81597876>] compat_SyS_fcntl64+0x836/0xa10 fs/compat.c:417
       [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
       [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
       [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a

       [<ffffffff81202d86>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
       [<ffffffff81202d86>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
       [<ffffffff81202d86>] validate_chain kernel/locking/lockdep.c:2144 [inline]
       [<ffffffff81202d86>] __lock_acquire+0x37d6/0x4f50 kernel/locking/lockdep.c:3213
       [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82717c98>] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline]
       [<ffffffff82717c98>] _raw_spin_lock+0x38/0x50 kernel/locking/spinlock.c:151
       [<ffffffff823ba312>] spin_lock include/linux/spinlock.h:302 [inline]
       [<ffffffff823ba312>] ip_defrag+0x322/0x3b70 net/ipv4/ip_fragment.c:690
       [<ffffffff823bdf36>] ip_check_defrag net/ipv4/ip_fragment.c:738 [inline]
       [<ffffffff823bdf36>] ip_check_defrag+0x3d6/0x5b0 net/ipv4/ip_fragment.c:705
       [<ffffffff826dfb3e>] packet_rcv_fanout+0x51e/0x5f0 net/packet/af_packet.c:1458
       [<ffffffff82244b38>] deliver_skb net/core/dev.c:1842 [inline]
       [<ffffffff82244b38>] dev_queue_xmit_nit net/core/dev.c:1898 [inline]
       [<ffffffff82244b38>] xmit_one net/core/dev.c:2777 [inline]
       [<ffffffff82244b38>] dev_hard_start_xmit+0x288/0x11e0 net/core/dev.c:2797
       [<ffffffff822b1bd6>] sch_direct_xmit+0x2b6/0x700 net/sched/sch_generic.c:165
       [<ffffffff82246aa4>] __dev_xmit_skb net/core/dev.c:2979 [inline]
       [<ffffffff82246aa4>] __dev_queue_xmit+0xd24/0x1bb0 net/core/dev.c:3197
       [<ffffffff82247948>] dev_queue_xmit+0x18/0x20 net/core/dev.c:3263
       [<ffffffff823c5962>] neigh_hh_output include/net/neighbour.h:486 [inline]
       [<ffffffff823c5962>] dst_neigh_output include/net/dst.h:459 [inline]
       [<ffffffff823c5962>] ip_finish_output2+0xbf2/0x1280 net/ipv4/ip_output.c:213
       [<ffffffff823c805c>] ip_do_fragment+0x187c/0x1f70 net/ipv4/ip_output.c:635
       [<ffffffff823cbd7b>] ip_fragment.constprop.0+0x14b/0x200 net/ipv4/ip_output.c:505
       [<ffffffff823cc1e9>] ip_finish_output+0x3b9/0xc60 net/ipv4/ip_output.c:286
       [<ffffffff823cf9f1>] NF_HOOK_COND include/linux/netfilter.h:240 [inline]
       [<ffffffff823cf9f1>] ip_mc_output+0x251/0xae0 net/ipv4/ip_output.c:347
       [<ffffffff823cd21c>] dst_output include/net/dst.h:498 [inline]
       [<ffffffff823cd21c>] ip_local_out+0x9c/0x180 net/ipv4/ip_output.c:119
       [<ffffffff823d300e>] ip_send_skb+0x3e/0xc0 net/ipv4/ip_output.c:1453
       [<ffffffff82478ded>] udp_send_skb+0x4fd/0xc70 net/ipv4/udp.c:842
       [<ffffffff824795ae>] udp_push_pending_frames+0x4e/0xe0 net/ipv4/udp.c:870
       [<ffffffff8248084e>] udp_sendpage+0x2ae/0x410 net/ipv4/udp.c:1183
       [<ffffffff824aa083>] inet_sendpage+0x223/0x520 net/ipv4/af_inet.c:772
       [<ffffffff821d81b5>] kernel_sendpage+0x95/0xf0 net/socket.c:3320
       [<ffffffff821d829b>] sock_sendpage+0x8b/0xc0 net/socket.c:793
       [<ffffffff81530f1d>] pipe_to_sendpage+0x28d/0x3d0 fs/splice.c:724
       [<ffffffff81533b6e>] splice_from_pipe_feed fs/splice.c:776 [inline]
       [<ffffffff81533b6e>] __splice_from_pipe+0x37e/0x7a0 fs/splice.c:901
       [<ffffffff81536be8>] splice_from_pipe+0x108/0x170 fs/splice.c:936
       [<ffffffff81536c8c>] generic_splice_sendpage+0x3c/0x50 fs/splice.c:1109
       [<ffffffff81537d31>] do_splice_from fs/splice.c:1128 [inline]
       [<ffffffff81537d31>] do_splice fs/splice.c:1404 [inline]
       [<ffffffff81537d31>] SYSC_splice fs/splice.c:1707 [inline]
       [<ffffffff81537d31>] SyS_splice+0xd71/0x13a0 fs/splice.c:1690
       [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
       [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
       [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(_xmit_NETROM);
                               lock(&(&q->lock)->rlock);
                               lock(_xmit_NETROM);
  lock(&(&q->lock)->rlock);

 *** DEADLOCK ***

6 locks held by syz-executor.3/14002:
 #0:  (&pipe->mutex/1){+.+.+.}, at: [<ffffffff814af8b3>] pipe_lock_nested fs/pipe.c:65 [inline]
 #0:  (&pipe->mutex/1){+.+.+.}, at: [<ffffffff814af8b3>] pipe_lock+0x63/0x80 fs/pipe.c:73
 #1:  (sk_lock-AF_INET){+.+.+.}, at: [<ffffffff824806d2>] lock_sock include/net/sock.h:1497 [inline]
 #1:  (sk_lock-AF_INET){+.+.+.}, at: [<ffffffff824806d2>] udp_sendpage+0x132/0x410 net/ipv4/udp.c:1160
 #2:  (rcu_read_lock_bh){......}, at: [<ffffffff823c4f7b>] ip_finish_output2+0x20b/0x1280 net/ipv4/ip_output.c:193
 #3:  (rcu_read_lock_bh){......}, at: [<ffffffff82245f57>] __dev_queue_xmit+0x1d7/0x1bb0 net/core/dev.c:3161
 #4:  (_xmit_NETROM){+.-...}, at: [<ffffffff822b1b58>] spin_lock include/linux/spinlock.h:302 [inline]
 #4:  (_xmit_NETROM){+.-...}, at: [<ffffffff822b1b58>] __netif_tx_lock include/linux/netdevice.h:3306 [inline]
 #4:  (_xmit_NETROM){+.-...}, at: [<ffffffff822b1b58>] sch_direct_xmit+0x238/0x700 net/sched/sch_generic.c:163
 #5:  (rcu_read_lock){......}, at: [<ffffffff82244963>] xmit_one net/core/dev.c:2776 [inline]
 #5:  (rcu_read_lock){......}, at: [<ffffffff82244963>] dev_hard_start_xmit+0xb3/0x11e0 net/core/dev.c:2797

stack backtrace:
CPU: 1 PID: 14002 Comm: syz-executor.3 Not tainted 4.4.174+ #17
 0000000000000000 6bb03207ec2672a5 ffff8801d758ecd0 ffffffff81aad1a1
 ffffffff84057a80 ffff8800b4325f00 ffffffff83adb8b0 ffffffff83ad4e60
 ffffffff83adb8b0 ffff8801d758ed20 ffffffff813abcda ffff8801d758ee00
Call Trace:
 [<ffffffff81aad1a1>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81aad1a1>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<ffffffff813abcda>] print_circular_bug.cold+0x2f7/0x44e kernel/locking/lockdep.c:1226
 [<ffffffff81202d86>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
 [<ffffffff81202d86>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
 [<ffffffff81202d86>] validate_chain kernel/locking/lockdep.c:2144 [inline]
 [<ffffffff81202d86>] __lock_acquire+0x37d6/0x4f50 kernel/locking/lockdep.c:3213
 [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff82717c98>] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline]
 [<ffffffff82717c98>] _raw_spin_lock+0x38/0x50 kernel/locking/spinlock.c:151
 [<ffffffff823ba312>] spin_lock include/linux/spinlock.h:302 [inline]
 [<ffffffff823ba312>] ip_defrag+0x322/0x3b70 net/ipv4/ip_fragment.c:690
 [<ffffffff823bdf36>] ip_check_defrag net/ipv4/ip_fragment.c:738 [inline]
 [<ffffffff823bdf36>] ip_check_defrag+0x3d6/0x5b0 net/ipv4/ip_fragment.c:705
 [<ffffffff826dfb3e>] packet_rcv_fanout+0x51e/0x5f0 net/packet/af_packet.c:1458
 [<ffffffff82244b38>] deliver_skb net/core/dev.c:1842 [inline]
 [<ffffffff82244b38>] dev_queue_xmit_nit net/core/dev.c:1898 [inline]
 [<ffffffff82244b38>] xmit_one net/core/dev.c:2777 [inline]
 [<ffffffff82244b38>] dev_hard_start_xmit+0x288/0x11e0 net/core/dev.c:2797
 [<ffffffff822b1bd6>] sch_direct_xmit+0x2b6/0x700 net/sched/sch_generic.c:165
 [<ffffffff82246aa4>] __dev_xmit_skb net/core/dev.c:2979 [inline]
 [<ffffffff82246aa4>] __dev_queue_xmit+0xd24/0x1bb0 net/core/dev.c:3197
 [<ffffffff82247948>] dev_queue_xmit+0x18/0x20 net/core/dev.c:3263
 [<ffffffff823c5962>] neigh_hh_output include/net/neighbour.h:486 [inline]
 [<ffffffff823c5962>] dst_neigh_output include/net/dst.h:459 [inline]
 [<ffffffff823c5962>] ip_finish_output2+0xbf2/0x1280 net/ipv4/ip_output.c:213
 [<ffffffff823c805c>] ip_do_fragment+0x187c/0x1f70 net/ipv4/ip_output.c:635
 [<ffffffff823cbd7b>] ip_fragment.constprop.0+0x14b/0x200 net/ipv4/ip_output.c:505
 [<ffffffff823cc1e9>] ip_finish_output+0x3b9/0xc60 net/ipv4/ip_output.c:286
 [<ffffffff823cf9f1>] NF_HOOK_COND include/linux/netfilter.h:240 [inline]
 [<ffffffff823cf9f1>] ip_mc_output+0x251/0xae0 net/ipv4/ip_output.c:347
 [<ffffffff823cd21c>] dst_output include/net/dst.h:498 [inline]
 [<ffffffff823cd21c>] ip_local_out+0x9c/0x180 net/ipv4/ip_output.c:119
 [<ffffffff823d300e>] ip_send_skb+0x3e/0xc0 net/ipv4/ip_output.c:1453
 [<ffffffff82478ded>] udp_send_skb+0x4fd/0xc70 net/ipv4/udp.c:842
 [<ffffffff824795ae>] udp_push_pending_frames+0x4e/0xe0 net/ipv4/udp.c:870
 [<ffffffff8248084e>] udp_sendpage+0x2ae/0x410 net/ipv4/udp.c:1183
 [<ffffffff824aa083>] inet_sendpage+0x223/0x520 net/ipv4/af_inet.c:772
 [<ffffffff821d81b5>] kernel_sendpage+0x95/0xf0 net/socket.c:3320
 [<ffffffff821d829b>] sock_sendpage+0x8b/0xc0 net/socket.c:793
 [<ffffffff81530f1d>] pipe_to_sendpage+0x28d/0x3d0 fs/splice.c:724
 [<ffffffff81533b6e>] splice_from_pipe_feed fs/splice.c:776 [inline]
 [<ffffffff81533b6e>] __splice_from_pipe+0x37e/0x7a0 fs/splice.c:901
 [<ffffffff81536be8>] splice_from_pipe+0x108/0x170 fs/splice.c:936
 [<ffffffff81536c8c>] generic_splice_sendpage+0x3c/0x50 fs/splice.c:1109
 [<ffffffff81537d31>] do_splice_from fs/splice.c:1128 [inline]
 [<ffffffff81537d31>] do_splice fs/splice.c:1404 [inline]
 [<ffffffff81537d31>] SYSC_splice fs/splice.c:1707 [inline]
 [<ffffffff81537d31>] SyS_splice+0xd71/0x13a0 fs/splice.c:1690
 [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
 [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
 [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a
audit: type=1400 audit(1568821899.078:37): avc:  denied  { transition } for  pid=14107 comm="syz-executor.4" path=2F6D656D66643AE6B47F9C31A6656D3070726B63656D30202864656C6574656429 dev="tmpfs" ino=50994 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:devicekit_var_run_t:s0 tclass=process permissive=1
audit: type=1400 audit(1568821899.228:38): avc:  denied  { entrypoint } for  pid=14107 comm="syz-executor.4" path=2F6D656D66643AE6B47F9C31A6656D3070726B63656D30202864656C6574656429 dev="tmpfs" ino=50994 scontext=system_u:object_r:devicekit_var_run_t:s0 tcontext=unconfined_u:object_r:tmpfs_t:s0 tclass=file permissive=1
audit: type=1400 audit(1568821899.388:39): avc:  denied  { share } for  pid=14107 comm="syz-executor.4" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:devicekit_var_run_t:s0 tclass=process permissive=1
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket
audit: type=1400 audit(1568821899.838:40): avc:  denied  { relabelto } for  pid=14274 comm="syz-executor.1" name="bus" dev="sda1" ino=16484 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:crypt_device_t:s0 tclass=file permissive=1
audit: type=1400 audit(1568821900.058:41): avc:  denied  { read write } for  pid=14274 comm="syz-executor.1" name="bus" dev="sda1" ino=16484 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:crypt_device_t:s0 tclass=file permissive=1
audit: type=1400 audit(1568821900.098:42): avc:  denied  { relabelfrom } for  pid=14274 comm="syz-executor.1" name="bus" dev="sda1" ino=16484 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:crypt_device_t:s0 tclass=file permissive=1
audit: type=1400 audit(1568821900.188:43): avc:  denied  { open } for  pid=14274 comm="syz-executor.1" path="/syzcgroup/cpu/syz1/bus" dev="sda1" ino=16484 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:crypt_device_t:s0 tclass=file permissive=1