IPVS: Creating netns size=2552 id=1
==================================================================
BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830
Read of size 4 at addr ffff8801d94e1b80 by task syz-executor0/4056

CPU: 0 PID: 4056 Comm: syz-executor0 Not tainted 4.4.141-g1b37d68 #7
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 c9ca330f249731f4 ffff8800b7bd7c78 ffffffff81e0e18d
 ffffea0007653800 ffff8801d94e1b80 0000000000000000 ffff8801d94e1b80
 ffffffff82f1a380 ffff8800b7bd7cb0 ffffffff81515a86 ffff8801d94e1b80
Call Trace:
 [<ffffffff81e0e18d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e0e18d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff81515a86>] print_address_description+0x6c/0x216 mm/kasan/report.c:252
 [<ffffffff81515da5>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff81515da5>] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408
 [<ffffffff814f9874>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428
 [<ffffffff8359b224>] l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830
 [<ffffffff835a7d5f>] pppol2tp_release+0x1ff/0x310 net/l2tp/l2tp_ppp.c:509
 [<ffffffff82f1a256>] sock_release+0x96/0x1c0 net/socket.c:586
 [<ffffffff82f1a396>] sock_close+0x16/0x20 net/socket.c:1037
 [<ffffffff81522e75>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff815233b5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118bdbf>] 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
 [<ffffffff81007090>] prepare_exit_to_usermode arch/x86/entry/common.c:284 [inline]
 [<ffffffff81007090>] syscall_return_slowpath arch/x86/entry/common.c:349 [inline]
 [<ffffffff81007090>] do_syscall_32_irqs_on arch/x86/entry/common.c:399 [inline]
 [<ffffffff81007090>] do_fast_syscall_32+0x620/0x8b0 arch/x86/entry/common.c:460
 [<ffffffff838c456a>] sysenter_flags_fixed+0xd/0x17

Allocated by task 4056:
 [<ffffffff81033c86>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814f8943>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814f8c27>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814f8c27>] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814f5344>] __kmalloc+0x124/0x310 mm/slub.c:3613
 [<ffffffff835a0669>] kmalloc include/linux/slab.h:481 [inline]
 [<ffffffff835a0669>] kzalloc include/linux/slab.h:620 [inline]
 [<ffffffff835a0669>] l2tp_session_create+0x39/0x1030 net/l2tp/l2tp_core.c:1748
 [<ffffffff835a5370>] pppol2tp_connect+0x10f0/0x1910 net/l2tp/l2tp_ppp.c:725
 [<ffffffff82f1ec78>] SYSC_connect+0x1b8/0x300 net/socket.c:1557
 [<ffffffff82f215b4>] SyS_connect+0x24/0x30 net/socket.c:1538
 [<ffffffff81006d96>] do_syscall_32_irqs_on arch/x86/entry/common.c:393 [inline]
 [<ffffffff81006d96>] do_fast_syscall_32+0x326/0x8b0 arch/x86/entry/common.c:460
 [<ffffffff838c456a>] sysenter_flags_fixed+0xd/0x17

Freed by task 4055:
 [<ffffffff81033c86>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814f8943>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814f9272>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814f9272>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814f6774>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814f6774>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814f6774>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814f6774>] kfree+0xf4/0x310 mm/slub.c:3749
 [<ffffffff8359d5d0>] l2tp_session_free+0x170/0x200 net/l2tp/l2tp_core.c:1676
 [<ffffffff8359f989>] l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:293 [inline]
 [<ffffffff8359f989>] l2tp_tunnel_closeall+0x2b9/0x350 net/l2tp/l2tp_core.c:1279
 [<ffffffff835a049b>] l2tp_udp_encap_destroy+0x8b/0xf0 net/l2tp/l2tp_core.c:1300
 [<ffffffff834927c1>] udpv6_destroy_sock+0xb1/0xd0 net/ipv6/udp.c:1421
 [<ffffffff82f2fb2d>] sk_common_release+0x6d/0x300 net/core/sock.c:2680
 [<ffffffff83491475>] udp_lib_close+0x15/0x20 include/net/udp.h:190
 [<ffffffff832f8f2f>] inet_release+0xff/0x1d0 net/ipv4/af_inet.c:435
 [<ffffffff8341bba0>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:424
 [<ffffffff82f1a256>] sock_release+0x96/0x1c0 net/socket.c:586
 [<ffffffff82f1a396>] sock_close+0x16/0x20 net/socket.c:1037
 [<ffffffff81522e75>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff815233b5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118bdbf>] 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
 [<ffffffff81007090>] prepare_exit_to_usermode arch/x86/entry/common.c:284 [inline]
 [<ffffffff81007090>] syscall_return_slowpath arch/x86/entry/common.c:349 [inline]
 [<ffffffff81007090>] do_syscall_32_irqs_on arch/x86/entry/common.c:399 [inline]
 [<ffffffff81007090>] do_fast_syscall_32+0x620/0x8b0 arch/x86/entry/common.c:460
 [<ffffffff838c456a>] sysenter_flags_fixed+0xd/0x17

The buggy address belongs to the object at ffff8801d94e1b80
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 512-byte region [ffff8801d94e1b80, ffff8801d94e1d80)
The buggy address belongs to the page:
------------[ cut here ]------------
WARNING: CPU: 1 PID: 0 at kernel/locking/lockdep.c:973 lock_accessed kernel/locking/lockdep.c:973 [inline]()
WARNING: CPU: 1 PID: 0 at kernel/locking/lockdep.c:973 __bfs+0x2aa/0x5f0 kernel/locking/lockdep.c:1040()