==================================================================
BUG: KASAN: use-after-free in __lock_acquire+0x3c66/0x5270 kernel/locking/lockdep.c:3092
Read of size 8 at addr ffff8800afc7de20 by task syz-executor0/10653

CPU: 1 PID: 10653 Comm: syz-executor0 Not tainted 4.4.150-g5541782 #83
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 10fbfb7a58a3cede ffff8801d797fa70 ffffffff81e14e2d
 ffffea0002bf1e00 ffff8800afc7de20 0000000000000000 ffff8800afc7de20
 0000000000000000 ffff8801d797faa8 ffffffff8151a3f0 ffff8800afc7de20
Call Trace:
 [<ffffffff81e14e2d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e14e2d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff8151a3f0>] print_address_description+0x6c/0x216 mm/kasan/report.c:252
 [<ffffffff8151a70f>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff8151a70f>] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408
 [<ffffffff814fdca4>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
 [<ffffffff81235c46>] __lock_acquire+0x3c66/0x5270 kernel/locking/lockdep.c:3092
 [<ffffffff81238a2e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff838ca32a>] __raw_spin_lock_bh include/linux/spinlock_api_smp.h:137 [inline]
 [<ffffffff838ca32a>] _raw_spin_lock_bh+0x3a/0x50 kernel/locking/spinlock.c:175
 [<ffffffff82f2e4a3>] spin_lock_bh include/linux/spinlock.h:307 [inline]
 [<ffffffff82f2e4a3>] lock_sock_nested+0x43/0x120 net/core/sock.c:2451
 [<ffffffff835afff0>] lock_sock include/net/sock.h:1493 [inline]
 [<ffffffff835afff0>] pppol2tp_release+0x50/0x310 net/l2tp/l2tp_ppp.c:493
 [<ffffffff82f21c86>] sock_release+0x96/0x1c0 net/socket.c:587
 [<ffffffff82f21dc6>] sock_close+0x16/0x20 net/socket.c:1038
 [<ffffffff815277d5>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff81527d15>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118ed2f>] 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
 [<ffffffff838cb235>] int_ret_from_sys_call+0x25/0xa3

Allocated by task 10660:
 [<ffffffff81034676>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fcd53>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fd037>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fd037>] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814f9774>] __kmalloc+0x124/0x310 mm/slub.c:3613
 [<ffffffff82f2d364>] kmalloc include/linux/slab.h:481 [inline]
 [<ffffffff82f2d364>] sk_prot_alloc+0x204/0x300 net/core/sock.c:1354
 [<ffffffff82f32d3a>] sk_alloc+0x3a/0x3a0 net/core/sock.c:1419
 [<ffffffff835abf13>] pppol2tp_create+0x33/0x1f0 net/l2tp/l2tp_ppp.c:551
 [<ffffffff828f8cd6>] pppox_create+0xf6/0x200 drivers/net/ppp/pppox.c:121
 [<ffffffff82f281b0>] __sock_create+0x2f0/0x5f0 net/socket.c:1178
 [<ffffffff82f286e0>] sock_create net/socket.c:1218 [inline]
 [<ffffffff82f286e0>] SYSC_socket net/socket.c:1248 [inline]
 [<ffffffff82f286e0>] SyS_socket+0xf0/0x1b0 net/socket.c:1228
 [<ffffffff838cb0a5>] entry_SYSCALL_64_fastpath+0x22/0x9e

Freed by task 10653:
 [<ffffffff81034676>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fcd53>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fd682>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fd682>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814fabe4>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814fabe4>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814fabe4>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814fabe4>] kfree+0xf4/0x310 mm/slub.c:3749
 [<ffffffff82f371f7>] sk_prot_free net/core/sock.c:1391 [inline]
 [<ffffffff82f371f7>] sk_destruct+0x407/0x4c0 net/core/sock.c:1472
 [<ffffffff82f372ff>] __sk_free+0x4f/0x220 net/core/sock.c:1480
 [<ffffffff82f37500>] sk_free+0x30/0x40 net/core/sock.c:1491
 [<ffffffff835af4cf>] sock_put include/net/sock.h:1639 [inline]
 [<ffffffff835af4cf>] pppol2tp_session_sock_put+0x5f/0x70 net/l2tp/l2tp_ppp.c:286
 [<ffffffff835a7d4c>] l2tp_tunnel_closeall+0x23c/0x350 net/l2tp/l2tp_core.c:1277
 [<ffffffff835a88db>] l2tp_udp_encap_destroy+0x8b/0xf0 net/l2tp/l2tp_core.c:1300
 [<ffffffff8349a8e1>] udpv6_destroy_sock+0xb1/0xd0 net/ipv6/udp.c:1421
 [<ffffffff82f3757d>] sk_common_release+0x6d/0x300 net/core/sock.c:2680
 [<ffffffff83499595>] udp_lib_close+0x15/0x20 include/net/udp.h:190
 [<ffffffff83300eff>] inet_release+0xff/0x1d0 net/ipv4/af_inet.c:435
 [<ffffffff83423b90>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:424
 [<ffffffff82f21c86>] sock_release+0x96/0x1c0 net/socket.c:587
 [<ffffffff82f21dc6>] sock_close+0x16/0x20 net/socket.c:1038
 [<ffffffff815277d5>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff81527d15>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118ed2f>] 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
 [<ffffffff838cb235>] int_ret_from_sys_call+0x25/0xa3

The buggy address belongs to the object at ffff8800afc7dd80
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 160 bytes inside of
 2048-byte region [ffff8800afc7dd80, ffff8800afc7e580)
The buggy address belongs to the page:
------------[ cut here ]------------
WARNING: CPU: 1 PID: -1345856128 at kernel/locking/lockdep.c:3123 __lock_acquire+0x23b8/0x5270 kernel/locking/lockdep.c:3123()
DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH)