IPv4: Oversized IP packet from 127.0.0.1
==================================================================
BUG: KASAN: use-after-free in pppol2tp_connect+0x160a/0x1910 net/l2tp/l2tp_ppp.c:735
Read of size 8 at addr ffff8801d6f1e190 by task syz-executor5/9842

CPU: 0 PID: 9842 Comm: syz-executor5 Not tainted 4.4.147-ga5fc665 #16
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 b391bf6135f6d932 ffff8801d4837ab0 ffffffff81e12a4d
 ffffea00075bc780 ffff8801d6f1e190 0000000000000000 ffff8801d6f1e190
 ffff8801d4837cd8 ffff8801d4837ae8 ffffffff81517fd6 ffff8801d6f1e190
Call Trace:
 [<ffffffff81e12a4d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e12a4d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff81517fd6>] print_address_description+0x6c/0x216 mm/kasan/report.c:252
 [<ffffffff815182f5>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff815182f5>] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408
 [<ffffffff814fbde4>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
 [<ffffffff835ab86a>] pppol2tp_connect+0x160a/0x1910 net/l2tp/l2tp_ppp.c:735
 [<ffffffff82f24298>] SYSC_connect+0x1b8/0x300 net/socket.c:1558
 [<ffffffff82f26bd4>] 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
 [<ffffffff838ca5c3>] sysenter_flags_fixed+0xd/0x1a

Allocated by task 9842:
 [<ffffffff81034676>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fae93>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fb177>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fb177>] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814f7894>] __kmalloc+0x124/0x310 mm/slub.c:3613
 [<ffffffff835a6649>] kmalloc include/linux/slab.h:481 [inline]
 [<ffffffff835a6649>] kzalloc include/linux/slab.h:620 [inline]
 [<ffffffff835a6649>] l2tp_session_create+0x39/0x1030 net/l2tp/l2tp_core.c:1748
 [<ffffffff835ab350>] pppol2tp_connect+0x10f0/0x1910 net/l2tp/l2tp_ppp.c:725
 [<ffffffff82f24298>] SYSC_connect+0x1b8/0x300 net/socket.c:1558
 [<ffffffff82f26bd4>] 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
 [<ffffffff838ca5c3>] sysenter_flags_fixed+0xd/0x1a

Freed by task 9837:
 [<ffffffff81034676>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fae93>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fb7c2>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fb7c2>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814f8cc4>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814f8cc4>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814f8cc4>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814f8cc4>] kfree+0xf4/0x310 mm/slub.c:3749
 [<ffffffff835a35b0>] l2tp_session_free+0x170/0x200 net/l2tp/l2tp_core.c:1676
 [<ffffffff835acfd7>] l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:293 [inline]
 [<ffffffff835acfd7>] pppol2tp_session_destruct+0xd7/0x110 net/l2tp/l2tp_ppp.c:477
 [<ffffffff82f34a2c>] sk_destruct+0x4c/0x4c0 net/core/sock.c:1447
 [<ffffffff82f34eef>] __sk_free+0x4f/0x220 net/core/sock.c:1480
 [<ffffffff82f350f0>] sk_free+0x30/0x40 net/core/sock.c:1491
 [<ffffffff835addaa>] sock_put include/net/sock.h:1639 [inline]
 [<ffffffff835addaa>] pppol2tp_release+0x26a/0x310 net/l2tp/l2tp_ppp.c:518
 [<ffffffff82f1f876>] sock_release+0x96/0x1c0 net/socket.c:587
 [<ffffffff82f1f9b6>] sock_close+0x16/0x20 net/socket.c:1038
 [<ffffffff815253c5>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff81525905>] ____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
 [<ffffffff838ca5c3>] sysenter_flags_fixed+0xd/0x1a

The buggy address belongs to the object at ffff8801d6f1e000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 400 bytes inside of
 512-byte region [ffff8801d6f1e000, ffff8801d6f1e200)
The buggy address belongs to the page:
------------[ cut here ]------------
WARNING: CPU: 1 PID: 9806 at kernel/locking/lockdep.c:973 lock_accessed kernel/locking/lockdep.c:973 [inline]()
WARNING: CPU: 1 PID: 9806 at kernel/locking/lockdep.c:973 __bfs+0x2aa/0x5f0 kernel/locking/lockdep.c:1040()