PF_BRIDGE: RTM_SETLINK with unknown ifindex
==================================================================
BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830
Read of size 4 at addr ffff8800b3965900 by task syz-executor5/7265

CPU: 1 PID: 7265 Comm: syz-executor5 Not tainted 4.4.152-ge5c5f1f #89
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 9ad8714cd76e5108 ffff8801bd017cb8 ffffffff81e15fed
 ffffea0002ce5900 ffff8800b3965900 0000000000000000 ffff8800b3965900
 0000000000000000 ffff8801bd017cf0 ffffffff8151b489 ffff8800b3965900
Call Trace:
 [<ffffffff81e15fed>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e15fed>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff8151b489>] print_address_description+0x6c/0x216 mm/kasan/report.c:252
 [<ffffffff8151b7a8>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff8151b7a8>] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408
 [<ffffffff814fe714>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428
 [<ffffffff835a4b64>] l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830
 [<ffffffff835b166f>] pppol2tp_release+0x1ff/0x310 net/l2tp/l2tp_ppp.c:509
 [<ffffffff82f210c9>] __sock_release+0xd9/0x260 net/socket.c:592
 [<ffffffff82f21269>] sock_close+0x19/0x20 net/socket.c:1050
 [<ffffffff81528875>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff81528db5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118ee4f>] 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
 [<ffffffff81006535>] prepare_exit_to_usermode arch/x86/entry/common.c:284 [inline]
 [<ffffffff81006535>] syscall_return_slowpath+0x1b5/0x1f0 arch/x86/entry/common.c:349
 [<ffffffff838cc6f5>] int_ret_from_sys_call+0x25/0xa3

Allocated by task 7267:
 [<ffffffff81034676>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fd7d3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fdab7>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fdab7>] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814fa1f4>] __kmalloc+0x124/0x310 mm/slub.c:3613
 [<ffffffff835a9f79>] kmalloc include/linux/slab.h:481 [inline]
 [<ffffffff835a9f79>] kzalloc include/linux/slab.h:620 [inline]
 [<ffffffff835a9f79>] l2tp_session_create+0x39/0x1030 net/l2tp/l2tp_core.c:1748
 [<ffffffff835aec80>] pppol2tp_connect+0x10f0/0x1910 net/l2tp/l2tp_ppp.c:725
 [<ffffffff82f27bf8>] SYSC_connect+0x1b8/0x300 net/socket.c:1570
 [<ffffffff82f2a544>] SyS_connect+0x24/0x30 net/socket.c:1551
 [<ffffffff838cc565>] entry_SYSCALL_64_fastpath+0x22/0x9e

Freed by task 7267:
 [<ffffffff81034676>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fd7d3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fe102>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fe102>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814fb664>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814fb664>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814fb664>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814fb664>] kfree+0xf4/0x310 mm/slub.c:3749
 [<ffffffff835a6ee0>] l2tp_session_free+0x170/0x200 net/l2tp/l2tp_core.c:1676
 [<ffffffff835a9299>] l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:293 [inline]
 [<ffffffff835a9299>] l2tp_tunnel_closeall+0x2b9/0x350 net/l2tp/l2tp_core.c:1279
 [<ffffffff835a9dab>] l2tp_udp_encap_destroy+0x8b/0xf0 net/l2tp/l2tp_core.c:1300
 [<ffffffff832d56a8>] udp_destroy_sock+0x118/0x1a0 net/ipv4/udp.c:2056
 [<ffffffff82f38add>] sk_common_release+0x6d/0x300 net/core/sock.c:2680
 [<ffffffff832d36b5>] udp_lib_close+0x15/0x20 include/net/udp.h:190
 [<ffffffff8330244f>] inet_release+0xff/0x1d0 net/ipv4/af_inet.c:435
 [<ffffffff82f210c9>] __sock_release+0xd9/0x260 net/socket.c:592
 [<ffffffff82f21269>] sock_close+0x19/0x20 net/socket.c:1050
 [<ffffffff81528875>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff81528db5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118ee4f>] 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
 [<ffffffff81006535>] prepare_exit_to_usermode arch/x86/entry/common.c:284 [inline]
 [<ffffffff81006535>] syscall_return_slowpath+0x1b5/0x1f0 arch/x86/entry/common.c:349
 [<ffffffff838cc6f5>] int_ret_from_sys_call+0x25/0xa3

The buggy address belongs to the object at ffff8800b3965900
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 512-byte region [ffff8800b3965900, ffff8800b3965b00)
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: 3756 Comm: syz-executor5 Not tainted 4.4.152-ge5c5f1f #89
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800b28de000 task.stack: ffff8800a4d30000
RIP: 0010:[<ffffffff811a91cd>]  [<ffffffff811a91cd>] task_curr kernel/sched/core.c:1025 [inline]
RIP: 0010:[<ffffffff811a91cd>]  [<ffffffff811a91cd>] kick_process+0xdd/0x1c0 kernel/sched/core.c:1567
RSP: 0018:ffff8800a4d37a90  EFLAGS: 00010002
RAX: dffffc0000000000 RBX: 000000000001f540 RCX: 0000000000000000
RDX: 00000000a42a87d0 RSI: ffffffff81e75b5b RDI: 0000000521543e80
RBP: ffff8800a4d37ab0 R08: 1ffffffff09de9eb R09: 0000000000000001
R10: 0000000000000000 R11: ffff8800b28de000 R12: ffff8801d22d9800
R13: 00000000b3965b00 R14: 00000000b3965b00 R15: ffff8800bb943f40
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff8800b3965900 CR3: 000000000440c000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801d22d9800 0000000000000080 ffff8801d22d9800 0000000000000100
 ffff8800a4d37ad0 ffffffff81158b1f ffff8801d22d9800 dffffc0000000000
 ffff8800a4d37b28 ffffffff8115919b ffff880000000000 0000000000000000
Call Trace:
 [<ffffffff81158b1f>] signal_wake_up_state+0x5f/0x70 kernel/signal.c:660
 [<ffffffff8115919b>] signal_wake_up include/linux/sched.h:3332 [inline]
 [<ffffffff8115919b>] complete_signal+0x62b/0x790 kernel/signal.c:942
 [<ffffffff8115a6e5>] __send_signal+0x4d5/0x11b0 kernel/signal.c:1080
 [<ffffffff8115b40a>] send_signal+0x4a/0xc0 kernel/signal.c:1096
 [<ffffffff8115daf4>] do_send_sig_info+0xa4/0x130 kernel/signal.c:1151
 [<ffffffff8115dbb3>] send_sig_info+0x33/0x50 kernel/signal.c:1436
 [<ffffffff81329bed>] zap_pid_ns_processes+0x28d/0x690 kernel/pid_namespace.c:223
 [<ffffffff811394f1>] find_child_reaper kernel/exit.c:477 [inline]
 [<ffffffff811394f1>] forget_original_parent kernel/exit.c:563 [inline]
 [<ffffffff811394f1>] exit_notify kernel/exit.c:599 [inline]
 [<ffffffff811394f1>] do_exit+0x1c21/0x26b0 kernel/exit.c:776
 [<ffffffff8113e1f1>] do_group_exit+0x111/0x330 kernel/exit.c:885
 [<ffffffff8113e42d>] SYSC_exit_group kernel/exit.c:896 [inline]
 [<ffffffff8113e42d>] SyS_exit_group+0x1d/0x20 kernel/exit.c:894
 [<ffffffff838cc565>] entry_SYSCALL_64_fastpath+0x22/0x9e
Code: 04 02 84 c0 74 08 3c 03 0f 8e b4 00 00 00 48 b8 00 00 00 00 00 fc ff df 45 8b 6d 10 4a 8d 3c ed 80 66 a1 84 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 ae 00 00 00 4a 03 1c ed 80 66 a1 84 48 b8 00 
RIP  [<ffffffff811a91cd>] task_curr kernel/sched/core.c:1025 [inline]
RIP  [<ffffffff811a91cd>] kick_process+0xdd/0x1c0 kernel/sched/core.c:1567
 RSP <ffff8800a4d37a90>
---[ end trace 8227f88f47f90416 ]---