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kernel BUG at net/l2tp/l2tp_core.c:917!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 21531 Comm: syz-executor5 Not tainted 4.9.112-g9e79039 #7
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff88019ccb3000 task.stack: ffff8801d83d8000
RIP: 0010:[<ffffffff836bbc00>]  [<ffffffff836bbc00>] l2tp_session_queue_purge+0xe0/0x100 net/l2tp/l2tp_core.c:917
RSP: 0018:ffff8801d83dfad8  EFLAGS: 00010216
RAX: 0000000000040000 RBX: ffff8801d4707900 RCX: ffffc9000024f000
RDX: 000000000000035b RSI: ffffffff836bbc00 RDI: ffff8801d4707900
RBP: ffff8801d83dfb00 R08: ffff88019ccb38e8 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801d4707900
R13: ffff8801b682b760 R14: ffff8801c8bf82d8 R15: ffffffff83013be0
FS:  00007ffbcf578700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc9527e8000 CR3: 00000001d3715000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801c8bf8000 ffff8801d4707900 ffff8801b682b760 ffff8801c8bf82d8
 ffffffff83013be0 ffff8801d83dfb30 ffffffff836c789b ffff8801b682b740
 ffffffff8417a860 ffff8801b682b768 0000000000000000 ffff8801d83dfb60
Call Trace:
 [<ffffffff836c789b>] pppol2tp_release+0x1fb/0x2e0 net/l2tp/l2tp_ppp.c:492
 [<ffffffff83013ab6>] sock_release+0x96/0x1c0 net/socket.c:599
 [<ffffffff83013bf6>] sock_close+0x16/0x20 net/socket.c:1046
 [<ffffffff815782e3>] __fput+0x263/0x700 fs/file_table.c:208
 [<ffffffff81578805>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8119839c>] task_work_run+0x10c/0x180 kernel/task_work.c:116
 [<ffffffff8116aa73>] get_signal+0x1133/0x1450 kernel/signal.c:2151
 [<ffffffff81052637>] do_signal+0x87/0x19f0 arch/x86/kernel/signal.c:807
 [<ffffffff81005581>] exit_to_usermode_loop+0xe1/0x120 arch/x86/entry/common.c:157
 [<ffffffff810064d4>] prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline]
 [<ffffffff810064d4>] syscall_return_slowpath arch/x86/entry/common.c:260 [inline]
 [<ffffffff810064d4>] do_syscall_64+0x364/0x490 arch/x86/entry/common.c:287
 [<ffffffff839f9f53>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 2e ca fd 31 c0 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 86 2e ca fd 48 89 df e8 ee 7b 34 00 eb ca e8 77 2e ca fd 0f 0b e8 70 2e ca fd <0f> 0b 4c 89 ff e8 16 00 e8 fd eb a6 48 89 df e8 ec ff e7 fd e9 
RIP  [<ffffffff836bbc00>] l2tp_session_queue_purge+0xe0/0x100 net/l2tp/l2tp_core.c:917
 RSP <ffff8801d83dfad8>
---[ end trace 11341026f14ccca2 ]---