TCP: request_sock_TCP: Possible SYN flooding on port 20002. Sending cookies.  Check SNMP counters.
==================================================================
BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830
Read of size 4 at addr ffff8800b9021b80 by task syz-executor0/12576

CPU: 0 PID: 12576 Comm: syz-executor0 Not tainted 4.4.153-g5e24b4e #90
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 430f6172148a11d1 ffff8801bd71fa78 ffffffff81e162ed
 ffffea0002e40800 ffff8800b9021b80 0000000000000000 ffff8800b9021b80
 0000000000000000 ffff8801bd71fab0 ffffffff8151b4d9 ffff8800b9021b80
Call Trace:
 [<ffffffff81e162ed>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e162ed>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff8151b4d9>] print_address_description+0x6c/0x216 mm/kasan/report.c:252
 [<ffffffff8151b7f8>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff8151b7f8>] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408
 [<ffffffff814fe764>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428
 [<ffffffff835a4e64>] l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830
 [<ffffffff835b196f>] pppol2tp_release+0x1ff/0x310 net/l2tp/l2tp_ppp.c:509
 [<ffffffff82f213c9>] __sock_release+0xd9/0x260 net/socket.c:592
 [<ffffffff82f21569>] sock_close+0x19/0x20 net/socket.c:1050
 [<ffffffff815288c5>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff81528e05>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118ee9f>] task_work_run+0x10f/0x190 kernel/task_work.c:115
 [<ffffffff811622e0>] get_signal+0x1190/0x14b0 kernel/signal.c:2151
 [<ffffffff8100df4b>] do_signal+0x8b/0x1d30 arch/x86/kernel/signal.c:712
 [<ffffffff8100360a>] exit_to_usermode_loop+0x11a/0x160 arch/x86/entry/common.c:249
 [<ffffffff81006535>] prepare_exit_to_usermode arch/x86/entry/common.c:284 [inline]
 [<ffffffff81006535>] syscall_return_slowpath+0x1b5/0x1f0 arch/x86/entry/common.c:349
 [<ffffffff838cc9f5>] int_ret_from_sys_call+0x25/0xa3

Allocated by task 12588:
 [<ffffffff81034676>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fd823>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fdb07>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fdb07>] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814fa244>] __kmalloc+0x124/0x310 mm/slub.c:3613
 [<ffffffff835aa279>] kmalloc include/linux/slab.h:481 [inline]
 [<ffffffff835aa279>] kzalloc include/linux/slab.h:620 [inline]
 [<ffffffff835aa279>] l2tp_session_create+0x39/0x1030 net/l2tp/l2tp_core.c:1748
 [<ffffffff835aef80>] pppol2tp_connect+0x10f0/0x1910 net/l2tp/l2tp_ppp.c:725
 [<ffffffff82f27ef8>] SYSC_connect+0x1b8/0x300 net/socket.c:1570
 [<ffffffff82f2a844>] SyS_connect+0x24/0x30 net/socket.c:1551
 [<ffffffff838cc865>] entry_SYSCALL_64_fastpath+0x22/0x9e

Freed by task 12588:
 [<ffffffff81034676>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fd823>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fe152>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fe152>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814fb6b4>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814fb6b4>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814fb6b4>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814fb6b4>] kfree+0xf4/0x310 mm/slub.c:3749
 [<ffffffff835a71e0>] l2tp_session_free+0x170/0x200 net/l2tp/l2tp_core.c:1676
 [<ffffffff835a9599>] l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:293 [inline]
 [<ffffffff835a9599>] l2tp_tunnel_closeall+0x2b9/0x350 net/l2tp/l2tp_core.c:1279
 [<ffffffff835aa0ab>] l2tp_udp_encap_destroy+0x8b/0xf0 net/l2tp/l2tp_core.c:1300
 [<ffffffff8349bf11>] udpv6_destroy_sock+0xb1/0xd0 net/ipv6/udp.c:1421
 [<ffffffff82f38ddd>] sk_common_release+0x6d/0x300 net/core/sock.c:2680
 [<ffffffff8349abc5>] udp_lib_close+0x15/0x20 include/net/udp.h:190
 [<ffffffff8330274f>] inet_release+0xff/0x1d0 net/ipv4/af_inet.c:435
 [<ffffffff834251c0>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:424
 [<ffffffff82f213c9>] __sock_release+0xd9/0x260 net/socket.c:592
 [<ffffffff82f21569>] sock_close+0x19/0x20 net/socket.c:1050
 [<ffffffff815288c5>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff81528e05>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118ee9f>] 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
 [<ffffffff838cc9f5>] int_ret_from_sys_call+0x25/0xa3

The buggy address belongs to the object at ffff8800b9021b80
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 512-byte region [ffff8800b9021b80, ffff8800b9021d80)
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: 1 PID: 12538 Comm: syz-executor4 Not tainted 4.4.153-g5e24b4e #90
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d6bac800 task.stack: ffff8800a4540000
RIP: 0010:[<ffffffff815c9892>]  [<ffffffff815c9892>] constant_test_bit arch/x86/include/asm/bitops.h:311 [inline]
RIP: 0010:[<ffffffff815c9892>]  [<ffffffff815c9892>] buffer_mapped include/linux/buffer_head.h:122 [inline]
RIP: 0010:[<ffffffff815c9892>]  [<ffffffff815c9892>] __find_get_block_slow+0x222/0x330 fs/buffer.c:224
RSP: 0018:ffff8800a4547538  EFLAGS: 00010246
RAX: 0000000000000000 RBX: dffffc0000000000 RCX: ffffc90005c34000
RDX: 0000000000040000 RSI: ffffffff815c988b RDI: ffff8801bac21938
RBP: ffff8800a4547610 R08: ffffffff85367790 R09: 0000000000000000
R10: 0000000000000001 R11: ffff8801d6bac800 R12: ffff8801bac21930
R13: ffffea0002aeb100 R14: 0000000000000000 R15: ffff8801d9c112e0
FS:  00007fd0e74f9700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020e00000 CR3: 00000000b947a000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801d9c113a4 ffff8801d9c115d0 1ffff100148a8ead ffff8801d9c11140
 0000000000000001 00000000000004ac 0000000041b58ab3 ffffffff841dc1d3
 ffffffff815c9670 ffff8801d6bac800 dffffc0000000000 ffff8800a45475e0
Call Trace:
 [<ffffffff815cc5a9>] __find_get_block+0x269/0x550 fs/buffer.c:1371
 [<ffffffff815cce4c>] __getblk_gfp+0x2c/0x80 fs/buffer.c:1393
 [<ffffffff816d8e28>] sb_getblk include/linux/buffer_head.h:313 [inline]
 [<ffffffff816d8e28>] __ext4_get_inode_loc+0x348/0xf50 fs/ext4/inode.c:4054
 [<ffffffff816ecdc7>] ext4_get_inode_loc fs/ext4/inode.c:4167 [inline]
 [<ffffffff816ecdc7>] ext4_reserve_inode_write+0x57/0x180 fs/ext4/inode.c:5206
 [<ffffffff816ed063>] ext4_mark_inode_dirty+0x173/0xb80 fs/ext4/inode.c:5275
 [<ffffffff816fc91b>] ext4_dirty_inode+0x7b/0xa0 fs/ext4/inode.c:5337
 [<ffffffff815a5768>] __mark_inode_dirty+0x408/0x1360 fs/fs-writeback.c:2055
 [<ffffffff815cec61>] mark_inode_dirty include/linux/fs.h:1946 [inline]
 [<ffffffff815cec61>] generic_write_end+0x121/0x1d0 fs/buffer.c:2124
 [<ffffffff816f8ad4>] ext4_da_write_end+0x274/0xd60 fs/ext4/inode.c:2921
 [<ffffffff81421199>] generic_perform_write+0x3d9/0x540 mm/filemap.c:2602
 [<ffffffff814265b2>] __generic_file_write_iter+0x362/0x550 mm/filemap.c:2716
 [<ffffffff816cb1e5>] ext4_file_write_iter+0x405/0xc60 fs/ext4/file.c:171
 [<ffffffff815228cd>] new_sync_write fs/read_write.c:478 [inline]
 [<ffffffff815228cd>] __vfs_write+0x30d/0x3f0 fs/read_write.c:491
 [<ffffffff815244b1>] vfs_write+0x191/0x4e0 fs/read_write.c:538
 [<ffffffff81526ab9>] SYSC_write fs/read_write.c:585 [inline]
 [<ffffffff81526ab9>] SyS_write+0xd9/0x1c0 fs/read_write.c:577
 [<ffffffff838cc865>] entry_SYSCALL_64_fastpath+0x22/0x9e
Code: ff 49 8d 7e 08 48 89 f8 48 c1 e8 03 80 3c 18 00 0f 85 cd 00 00 00 4d 8b 76 08 4d 39 f4 74 29 e8 05 ad d8 ff 4c 89 f0 48 c1 e8 03 <80> 3c 18 00 0f 85 b8 00 00 00 49 8b 06 a8 20 75 95 c7 85 4c ff 
RIP  [<ffffffff815c9892>] constant_test_bit arch/x86/include/asm/bitops.h:311 [inline]
RIP  [<ffffffff815c9892>] buffer_mapped include/linux/buffer_head.h:122 [inline]
RIP  [<ffffffff815c9892>] __find_get_block_slow+0x222/0x330 fs/buffer.c:224
 RSP <ffff8800a4547538>
---[ end trace 9cbcea6b54daefbb ]---