BUG: sleeping function called from invalid context at net/core/sock.c:2502
in_atomic(): 1, irqs_disabled(): 0, pid: 28888, name: syz-executor5
1 lock held by syz-executor5/28888:
 #0:  (rcu_callback){......}, at: [<ffffffff81289ace>] __rcu_reclaim kernel/rcu/rcu.h:108 [inline]
 #0:  (rcu_callback){......}, at: [<ffffffff81289ace>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 #0:  (rcu_callback){......}, at: [<ffffffff81289ace>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 #0:  (rcu_callback){......}, at: [<ffffffff81289ace>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 #0:  (rcu_callback){......}, at: [<ffffffff81289ace>] rcu_process_callbacks+0x98e/0x12b0 kernel/rcu/tree.c:3037
Preemption disabled at:[  346.575635] [<ffffffff836cf871>] local_bh_disable include/linux/bottom_half.h:18 [inline]
Preemption disabled at:[  346.575635] [<ffffffff836cf871>] pppol2tp_sendmsg+0x4a1/0x790 net/l2tp/l2tp_ppp.c:338
CPU: 1 PID: 28888 Comm: syz-executor5 Not tainted 4.9.124-g09eb2ba #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801db307d10 ffffffff81eb95e9 ffffffff836cf871 0000000000000000
 0000000000000101 ffff8801b2efe000 ffff8801b2efe000 ffff8801db307d48
 ffffffff81426851 ffff8801b2efe000 ffffffff840f88a0 00000000000009c6
Call Trace:
 <IRQ> [  346.627597]  [<ffffffff81eb95e9>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [  346.627597]  [<ffffffff81eb95e9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81426851>] ___might_sleep.cold.123+0x1bc/0x1f5 kernel/sched/core.c:7988
 [<ffffffff811bd9a5>] __might_sleep+0x95/0x1a0 kernel/sched/core.c:7945
 [<ffffffff8302b774>] lock_sock_nested+0x34/0x120 net/core/sock.c:2502
 [<ffffffff83428dd9>] lock_sock include/net/sock.h:1404 [inline]
 [<ffffffff83428dd9>] inet_shutdown+0x69/0x360 net/ipv4/af_inet.c:823
 [<ffffffff836cb740>] pppol2tp_session_close+0xa0/0xe0 net/l2tp/l2tp_ppp.c:441
 [<ffffffff836c4f71>] l2tp_tunnel_closeall+0x231/0x350 net/l2tp/l2tp_core.c:1368
 [<ffffffff836c57f2>] l2tp_tunnel_destruct+0x2f2/0x590 net/l2tp/l2tp_core.c:1324
 [<ffffffff830281f5>] __sk_destruct+0x55/0x590 net/core/sock.c:1428
 [<ffffffff812899ee>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 [<ffffffff812899ee>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 [<ffffffff812899ee>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 [<ffffffff812899ee>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 [<ffffffff812899ee>] rcu_process_callbacks+0x8ae/0x12b0 kernel/rcu/tree.c:3037
 [<ffffffff83a085c0>] __do_softirq+0x210/0x940 kernel/softirq.c:288
 [<ffffffff83a029dc>] do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:843
 <EOI> [  346.745593]  [<ffffffff8114bb52>] do_softirq.part.14+0x62/0x70 kernel/softirq.c:332
 [<ffffffff8114bc28>] do_softirq arch/x86/include/asm/preempt.h:22 [inline]
 [<ffffffff8114bc28>] __local_bh_enable_ip+0xc8/0xd0 kernel/softirq.c:185
 [<ffffffff836cf8c6>] local_bh_enable include/linux/bottom_half.h:31 [inline]
 [<ffffffff836cf8c6>] pppol2tp_sendmsg+0x4f6/0x790 net/l2tp/l2tp_ppp.c:340
 [<ffffffff8301e0ac>] sock_sendmsg_nosec net/socket.c:648 [inline]
 [<ffffffff8301e0ac>] sock_sendmsg+0xcc/0x110 net/socket.c:658
 [<ffffffff8301f8ca>] ___sys_sendmsg+0x47a/0x840 net/socket.c:1982
 [<ffffffff83021e31>] __sys_sendmmsg+0x161/0x3d0 net/socket.c:2072
 [<ffffffff830220d5>] SYSC_sendmmsg net/socket.c:2103 [inline]
 [<ffffffff830220d5>] SyS_sendmmsg+0x35/0x60 net/socket.c:2098
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a019d3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

=================================
[ INFO: inconsistent lock state ]
4.9.124-g09eb2ba #31 Tainted: G        W      
---------------------------------
inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
syz-executor5/28888 [HC0[0]:SC1[3]:HE1:SE0] takes:
 (sk_lock-AF_PPPOX){+.?.+.}, at: [<ffffffff83428dd9>] lock_sock include/net/sock.h:1404 [inline]
 (sk_lock-AF_PPPOX){+.?.+.}, at: [<ffffffff83428dd9>] inet_shutdown+0x69/0x360 net/ipv4/af_inet.c:823
  mark_held_locks+0xc7/0x130 kernel/locking/lockdep.c:2660
  __trace_hardirqs_on_caller kernel/locking/lockdep.c:2689 [inline]
  trace_hardirqs_on_caller+0x38b/0x590 kernel/locking/lockdep.c:2736
  trace_hardirqs_on+0xd/0x10 kernel/locking/lockdep.c:2743
  __local_bh_enable_ip+0x6a/0xd0 kernel/softirq.c:190
  local_bh_enable include/linux/bottom_half.h:31 [inline]
  lock_sock_nested+0xdc/0x120 net/core/sock.c:2512
  lock_sock include/net/sock.h:1404 [inline]
  pppol2tp_release+0x50/0x2e0 net/l2tp/l2tp_ppp.c:476
  __sock_release+0xd7/0x260 net/socket.c:605
  sock_close+0x19/0x20 net/socket.c:1059
  __fput+0x263/0x700 fs/file_table.c:208
  ____fput+0x15/0x20 fs/file_table.c:244
  task_work_run+0x10c/0x180 kernel/task_work.c:116
  tracehook_notify_resume include/linux/tracehook.h:191 [inline]
  exit_to_usermode_loop+0xfc/0x120 arch/x86/entry/common.c:161
  prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline]
  syscall_return_slowpath arch/x86/entry/common.c:260 [inline]
  do_syscall_64+0x364/0x490 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_swapgs+0x5d/0xdb
irq event stamp: 3858
hardirqs last  enabled at (3858): [<ffffffff83a02369>] restore_regs_and_iret+0x0/0x1d
hardirqs last disabled at (3857): [<ffffffff83a0332b>] apic_timer_interrupt+0x9b/0xb0 arch/x86/entry/entry_64.S:648
softirqs last  enabled at (3494): [<ffffffff836cf89f>] pppol2tp_sendmsg+0x4cf/0x790 net/l2tp/l2tp_ppp.c:339
softirqs last disabled at (3495): [<ffffffff83a029dc>] do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:843

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(sk_lock-AF_PPPOX);
  <Interrupt>
    lock(sk_lock-AF_PPPOX);

 *** DEADLOCK ***

1 lock held by syz-executor5/28888:
 #0:  (rcu_callback){......}, at: [<ffffffff81289ace>] __rcu_reclaim kernel/rcu/rcu.h:108 [inline]
 #0:  (rcu_callback){......}, at: [<ffffffff81289ace>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 #0:  (rcu_callback){......}, at: [<ffffffff81289ace>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 #0:  (rcu_callback){......}, at: [<ffffffff81289ace>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 #0:  (rcu_callback){......}, at: [<ffffffff81289ace>] rcu_process_callbacks+0x98e/0x12b0 kernel/rcu/tree.c:3037

stack backtrace:
CPU: 1 PID: 28888 Comm: syz-executor5 Tainted: G        W       4.9.124-g09eb2ba #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801db307a88 ffffffff81eb95e9 ffff8801b2efe000 ffffffff85613ac0
 ffff8801b2efe8f0 ffff8801b2efe910 0000000000000000 ffff8801db307af8
 ffffffff81429ccd 0000000000000003 0000000000000001 ffff880100000000
Call Trace:
 <IRQ> [  347.150039]  [<ffffffff81eb95e9>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [  347.150039]  [<ffffffff81eb95e9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81429ccd>] print_usage_bug.cold.57+0x327/0x421 kernel/locking/lockdep.c:2387
 [<ffffffff81237726>] valid_state kernel/locking/lockdep.c:2400 [inline]
 [<ffffffff81237726>] mark_lock_irq kernel/locking/lockdep.c:2602 [inline]
 [<ffffffff81237726>] mark_lock+0xcc6/0x1280 kernel/locking/lockdep.c:3065
 [<ffffffff812390f0>] mark_irqflags kernel/locking/lockdep.c:2923 [inline]
 [<ffffffff812390f0>] __lock_acquire+0xd40/0x4070 kernel/locking/lockdep.c:3302
 [<ffffffff8123ce90>] lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756
 [<ffffffff8302b806>] lock_sock_nested+0xc6/0x120 net/core/sock.c:2511
 [<ffffffff83428dd9>] lock_sock include/net/sock.h:1404 [inline]
 [<ffffffff83428dd9>] inet_shutdown+0x69/0x360 net/ipv4/af_inet.c:823
 [<ffffffff836cb740>] pppol2tp_session_close+0xa0/0xe0 net/l2tp/l2tp_ppp.c:441
 [<ffffffff836c4f71>] l2tp_tunnel_closeall+0x231/0x350 net/l2tp/l2tp_core.c:1368
 [<ffffffff836c57f2>] l2tp_tunnel_destruct+0x2f2/0x590 net/l2tp/l2tp_core.c:1324
 [<ffffffff830281f5>] __sk_destruct+0x55/0x590 net/core/sock.c:1428
 [<ffffffff812899ee>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 [<ffffffff812899ee>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 [<ffffffff812899ee>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 [<ffffffff812899ee>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 [<ffffffff812899ee>] rcu_process_callbacks+0x8ae/0x12b0 kernel/rcu/tree.c:3037
 [<ffffffff83a085c0>] __do_softirq+0x210/0x940 kernel/softirq.c:288
 [<ffffffff83a029dc>] do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:843
 <EOI> [  347.327604]  [<ffffffff8114bb52>] do_softirq.part.14+0x62/0x70 kernel/softirq.c:332
 [<ffffffff8114bc28>] do_softirq arch/x86/include/asm/preempt.h:22 [inline]
 [<ffffffff8114bc28>] __local_bh_enable_ip+0xc8/0xd0 kernel/softirq.c:185
 [<ffffffff836cf8c6>] local_bh_enable include/linux/bottom_half.h:31 [inline]
 [<ffffffff836cf8c6>] pppol2tp_sendmsg+0x4f6/0x790 net/l2tp/l2tp_ppp.c:340
 [<ffffffff8301e0ac>] sock_sendmsg_nosec net/socket.c:648 [inline]
 [<ffffffff8301e0ac>] sock_sendmsg+0xcc/0x110 net/socket.c:658
 [<ffffffff8301f8ca>] ___sys_sendmsg+0x47a/0x840 net/socket.c:1982
 [<ffffffff83021e31>] __sys_sendmmsg+0x161/0x3d0 net/socket.c:2072
 [<ffffffff830220d5>] SYSC_sendmmsg net/socket.c:2103 [inline]
 [<ffffffff830220d5>] SyS_sendmmsg+0x35/0x60 net/socket.c:2098
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a019d3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
==================================================================
BUG: KASAN: use-after-free in l2tp_sock_to_tunnel net/l2tp/l2tp_core.h:234 [inline]
BUG: KASAN: use-after-free in pppol2tp_sendmsg+0x681/0x790 net/l2tp/l2tp_ppp.c:304
Read of size 8 at addr ffff8801b6111750 by task syz-executor5/28888

CPU: 1 PID: 28888 Comm: syz-executor5 Tainted: G        W       4.9.124-g09eb2ba #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801c10e78e0 ffffffff81eb95e9 ffffea0006d84400 ffff8801b6111750
 0000000000000000 ffff8801b6111750 ffff8801b6111380 ffff8801c10e7918
 ffffffff8156c35e ffff8801b6111750 0000000000000008 0000000000000000
Call Trace:
 [<ffffffff81eb95e9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb95e9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8156c35e>] print_address_description+0x6c/0x234 mm/kasan/report.c:256
 [<ffffffff8156c768>] kasan_report_error mm/kasan/report.c:355 [inline]
 [<ffffffff8156c768>] kasan_report.cold.6+0x242/0x2fe mm/kasan/report.c:412
 [<ffffffff8153faf4>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 [<ffffffff836cfa51>] l2tp_sock_to_tunnel net/l2tp/l2tp_core.h:234 [inline]
 [<ffffffff836cfa51>] pppol2tp_sendmsg+0x681/0x790 net/l2tp/l2tp_ppp.c:304
 [<ffffffff8301e0ac>] sock_sendmsg_nosec net/socket.c:648 [inline]
 [<ffffffff8301e0ac>] sock_sendmsg+0xcc/0x110 net/socket.c:658
 [<ffffffff8301f8ca>] ___sys_sendmsg+0x47a/0x840 net/socket.c:1982
 [<ffffffff83021e31>] __sys_sendmmsg+0x161/0x3d0 net/socket.c:2072
 [<ffffffff830220d5>] SYSC_sendmmsg net/socket.c:2103 [inline]
 [<ffffffff830220d5>] SyS_sendmmsg+0x35/0x60 net/socket.c:2098
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a019d3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Allocated by task 28883:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 save_stack+0x43/0xd0 mm/kasan/kasan.c:505
 set_track mm/kasan/kasan.c:517 [inline]
 kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:609
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:547
 slab_post_alloc_hook mm/slab.h:417 [inline]
 slab_alloc_node mm/slub.c:2715 [inline]
 slab_alloc mm/slub.c:2723 [inline]
 kmem_cache_alloc+0xbe/0x290 mm/slub.c:2728
 sk_prot_alloc+0x69/0x290 net/core/sock.c:1332
 sk_alloc+0x3a/0x3a0 net/core/sock.c:1394
 inet6_create+0x2d9/0xd80 net/ipv6/af_inet6.c:198
 __sock_create+0x2f1/0x5f0 net/socket.c:1195
 sock_create net/socket.c:1235 [inline]
 SYSC_socket net/socket.c:1265 [inline]
 SyS_socket+0xf0/0x1b0 net/socket.c:1245
 do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Freed by task 28888:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 save_stack+0x43/0xd0 mm/kasan/kasan.c:505
 set_track mm/kasan/kasan.c:517 [inline]
 kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:582
 slab_free_hook mm/slub.c:1355 [inline]
 slab_free_freelist_hook mm/slub.c:1377 [inline]
 slab_free mm/slub.c:2958 [inline]
 kmem_cache_free+0xbe/0x310 mm/slub.c:2980
 sk_prot_free net/core/sock.c:1375 [inline]
 __sk_destruct+0x3b9/0x590 net/core/sock.c:1455
 __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 rcu_process_callbacks+0x8ae/0x12b0 kernel/rcu/tree.c:3037
 __do_softirq+0x210/0x940 kernel/softirq.c:288

The buggy address belongs to the object at ffff8801b6111380
 which belongs to the cache UDPv6 of size 1496
The buggy address is located 976 bytes inside of
 1496-byte region [ffff8801b6111380, ffff8801b6111958)
The buggy address belongs to the page:
page:ffffea0006d84400 count:1 mapcount:0 mapping:          (null) index:0x0 compound_mapcount: 0
flags: 0x8000000000004080(slab|head)
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801b6111600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801b6111680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801b6111700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff8801b6111780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801b6111800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================