l2tp_core: tunl 3: sockfd_lookup(fd=14) returned -9
l2tp_core: tunl 3: sockfd_lookup(fd=8) returned -9
l2tp_core: tunl 3: sockfd_lookup(fd=14) returned -9
l2tp_core: tunl 3: sockfd_lookup(fd=8) returned -9
==================================================================
BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830
Read of size 4 at addr ffff8800b8da6780 by task syz-executor0/4364

CPU: 1 PID: 4364 Comm: syz-executor0 Not tainted 4.4.146-g1396226 #15
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 bc1a6ef50338adc0 ffff8801ccf1fc78 ffffffff81e1292d
 ffffea0002e36980 ffff8800b8da6780 0000000000000000 ffff8800b8da6780
 ffffffff82f1f7c0 ffff8801ccf1fcb0 ffffffff81517f76 ffff8800b8da6780
Call Trace:
 [<ffffffff81e1292d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e1292d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff81517f76>] print_address_description+0x6c/0x216 mm/kasan/report.c:252
 [<ffffffff81518295>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff81518295>] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408
 [<ffffffff814fbd64>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428
 [<ffffffff835a0ff4>] l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830
 [<ffffffff835adb2f>] pppol2tp_release+0x1ff/0x310 net/l2tp/l2tp_ppp.c:509
 [<ffffffff82f1f696>] sock_release+0x96/0x1c0 net/socket.c:587
 [<ffffffff82f1f7d6>] sock_close+0x16/0x20 net/socket.c:1038
 [<ffffffff81525365>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff815258a5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118e00f>] task_work_run+0x10f/0x190 kernel/task_work.c:115
 [<ffffffff8100362d>] tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 [<ffffffff8100362d>] exit_to_usermode_loop+0x13d/0x160 arch/x86/entry/common.c:253
 [<ffffffff8100708e>] prepare_exit_to_usermode arch/x86/entry/common.c:284 [inline]
 [<ffffffff8100708e>] syscall_return_slowpath arch/x86/entry/common.c:349 [inline]
 [<ffffffff8100708e>] do_syscall_32_irqs_on arch/x86/entry/common.c:399 [inline]
 [<ffffffff8100708e>] do_fast_syscall_32+0x61e/0x8b0 arch/x86/entry/common.c:460
 [<ffffffff838ca383>] sysenter_flags_fixed+0xd/0x1a

Allocated by task 4367:
 [<ffffffff81034676>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fae33>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fb117>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fb117>] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814f7834>] __kmalloc+0x124/0x310 mm/slub.c:3613
 [<ffffffff835a6439>] kmalloc include/linux/slab.h:481 [inline]
 [<ffffffff835a6439>] kzalloc include/linux/slab.h:620 [inline]
 [<ffffffff835a6439>] l2tp_session_create+0x39/0x1030 net/l2tp/l2tp_core.c:1748
 [<ffffffff835ab140>] pppol2tp_connect+0x10f0/0x1910 net/l2tp/l2tp_ppp.c:725
 [<ffffffff82f240b8>] SYSC_connect+0x1b8/0x300 net/socket.c:1558
 [<ffffffff82f269f4>] SyS_connect+0x24/0x30 net/socket.c:1539
 [<ffffffff81006d94>] do_syscall_32_irqs_on arch/x86/entry/common.c:393 [inline]
 [<ffffffff81006d94>] do_fast_syscall_32+0x324/0x8b0 arch/x86/entry/common.c:460
 [<ffffffff838ca383>] sysenter_flags_fixed+0xd/0x1a

Freed by task 4367:
 [<ffffffff81034676>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fae33>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fb762>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fb762>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814f8c64>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814f8c64>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814f8c64>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814f8c64>] kfree+0xf4/0x310 mm/slub.c:3749
 [<ffffffff835a33a0>] l2tp_session_free+0x170/0x200 net/l2tp/l2tp_core.c:1676
 [<ffffffff835a5759>] l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:293 [inline]
 [<ffffffff835a5759>] l2tp_tunnel_closeall+0x2b9/0x350 net/l2tp/l2tp_core.c:1279
 [<ffffffff835a626b>] l2tp_udp_encap_destroy+0x8b/0xf0 net/l2tp/l2tp_core.c:1300
 [<ffffffff83498271>] udpv6_destroy_sock+0xb1/0xd0 net/ipv6/udp.c:1421
 [<ffffffff82f34f8d>] sk_common_release+0x6d/0x300 net/core/sock.c:2680
 [<ffffffff83496f25>] udp_lib_close+0x15/0x20 include/net/udp.h:190
 [<ffffffff832fe88f>] inet_release+0xff/0x1d0 net/ipv4/af_inet.c:435
 [<ffffffff83421520>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:424
 [<ffffffff82f1f696>] sock_release+0x96/0x1c0 net/socket.c:587
 [<ffffffff82f1f7d6>] sock_close+0x16/0x20 net/socket.c:1038
 [<ffffffff81525365>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff815258a5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118e00f>] task_work_run+0x10f/0x190 kernel/task_work.c:115
 [<ffffffff8100362d>] tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 [<ffffffff8100362d>] exit_to_usermode_loop+0x13d/0x160 arch/x86/entry/common.c:253
 [<ffffffff8100708e>] prepare_exit_to_usermode arch/x86/entry/common.c:284 [inline]
 [<ffffffff8100708e>] syscall_return_slowpath arch/x86/entry/common.c:349 [inline]
 [<ffffffff8100708e>] do_syscall_32_irqs_on arch/x86/entry/common.c:399 [inline]
 [<ffffffff8100708e>] do_fast_syscall_32+0x61e/0x8b0 arch/x86/entry/common.c:460
 [<ffffffff838ca383>] sysenter_flags_fixed+0xd/0x1a

The buggy address belongs to the object at ffff8800b8da6780
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 512-byte region [ffff8800b8da6780, ffff8800b8da6980)
The buggy address belongs to the page:
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory accessgeneral protection fault: 0000 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.146-g1396226 #15
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffffffff84417840 task.stack: ffffffff84400000
RIP: 0010:[<ffffffff83522d67>]  [<ffffffff83522d67>] ip6t_do_table+0x297/0x17e0 net/ipv6/netfilter/ip6_tables.c:361
RSP: 0018:ffff8801db207680  EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffff8801ccf08000
RDX: 0000000000000000 RSI: ffffffff81e7245b RDI: ffff8801ccf08038
RBP: ffff8801db2078a0 R08: ffffffff84418190 R09: 0000000000000000
R10: 0000000000000001 R11: ffffffff84417840 R12: 0000000000000000
R13: ffff8801ce809b40 R14: ffff8801d48fa2a8 R15: ffff8801db207a40
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000f771ac30 CR3: 00000001cdf0f000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8118e1db ffffffff84407fe8 ffff8801db2076e8 ffffffff8101678b
 ffffffff84407fe8 ffff8801db207790 ffff8801cd4e1100 ffff8801ce809b60
 ffff880100010001 ffff8801ce200000 ffff8801db207700 1ffff1003b640edc
Call Trace:
 <IRQ> 
 [<ffffffff835299e5>] ip6table_raw_hook+0x65/0x80 net/ipv6/netfilter/ip6table_raw.c:25
 [<ffffffff830c77e2>] nf_iterate+0x182/0x210 net/netfilter/core.c:274
 [<ffffffff830c7a26>] nf_hook_slow+0x1b6/0x340 net/netfilter/core.c:306
 [<ffffffff8348b7b9>] nf_hook_thresh include/linux/netfilter.h:187 [inline]
 [<ffffffff8348b7b9>] NF_HOOK_THRESH.constprop.29+0x1c9/0x310 include/linux/netfilter.h:224
 [<ffffffff8348c4e7>] NF_HOOK include/linux/netfilter.h:249 [inline]
 [<ffffffff8348c4e7>] ndisc_send_skb+0x7e7/0xf20 net/ipv6/ndisc.c:471
 [<ffffffff834909aa>] ndisc_send_rs+0x12a/0x430 net/ipv6/ndisc.c:646
 [<ffffffff83452fc7>] addrconf_rs_timer+0x287/0x5b0 net/ipv6/addrconf.c:3527
 [<ffffffff81292d4c>] call_timer_fn+0x18c/0x870 kernel/time/timer.c:1185
PANIC: double fault, error_code: 0x0
CPU: 1 PID: 4364 Comm: syz-executor0 Not tainted 4.4.146-g1396226 #15
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800b1bb6000 task.stack: ffff8801ccf18000
RIP: 0010:[<ffffffff8148f44d>]  [<ffffffff8148f44d>] dump_page_badflags+0xd/0x70 mm/debug.c:84
RSP: 0018:ffff880100000000  EFLAGS: 00010046
RAX: ffff8800b1bb6000 RBX: ffffea0002e36980 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff83aaad60 RDI: ffffea0002e36980
RBP: ffff880100000018 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: ffffffff858f0274 R12: 0000000000000000
R13: ffffffff83aaad60 R14: ffff8800b8da6780 R15: ffff8800b8da6980
FS:  0000000000000000(0000) GS:ffff8801db300000(0063) knlGS:0000000009f2d900
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: ffff8800fffffff8 CR3: 00000001cd2ba000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:

Call Trace:
 <UNK> 
Code: f0 48 ff 80 28 5b 9f 84 5b 5d c3 48 89 df e8 3b c9 06 00 eb dd 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 57 41 56 41 55 49 89 f5 <41> 54 49 89 d4 53 48 89 fb 48 83 ec 08 e8 51 43 ec ff 48 89 da