==================================================================
BUG: KASAN: use-after-free in __lock_acquire+0x3c66/0x5270 kernel/locking/lockdep.c:3092
Read of size 8 at addr ffff8801d8b20920 by task syz-executor3/22706

CPU: 1 PID: 22706 Comm: syz-executor3 Not tainted 4.4.139-g7ba5557 #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 7e23a6c1c2a66737 ffff8801cdf1fa30 ffffffff81e0d58d
 ffffea000762c800 ffff8801d8b20920 0000000000000000 ffff8801d8b20920
 0000000000000000 ffff8801cdf1fa68 ffffffff81515a16 ffff8801d8b20920
Call Trace:
 [<ffffffff81e0d58d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e0d58d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff81515a16>] print_address_description+0x6c/0x216 mm/kasan/report.c:252
 [<ffffffff81515d35>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff81515d35>] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408
 [<ffffffff814f9824>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
 [<ffffffff81232c96>] __lock_acquire+0x3c66/0x5270 kernel/locking/lockdep.c:3092
 [<ffffffff81235a7e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff838c0aca>] __raw_spin_lock_bh include/linux/spinlock_api_smp.h:137 [inline]
 [<ffffffff838c0aca>] _raw_spin_lock_bh+0x3a/0x50 kernel/locking/spinlock.c:175
 [<ffffffff82f257e3>] spin_lock_bh include/linux/spinlock.h:307 [inline]
 [<ffffffff82f257e3>] lock_sock_nested+0x43/0x120 net/core/sock.c:2451
 [<ffffffff835a67f0>] lock_sock include/net/sock.h:1493 [inline]
 [<ffffffff835a67f0>] pppol2tp_release+0x50/0x310 net/l2tp/l2tp_ppp.c:493
 [<ffffffff82f18fd6>] sock_release+0x96/0x1c0 net/socket.c:586
 [<ffffffff82f19116>] sock_close+0x16/0x20 net/socket.c:1037
 [<ffffffff81522e05>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff81523345>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118bd7f>] 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:252
 [<ffffffff81007090>] prepare_exit_to_usermode arch/x86/entry/common.c:283 [inline]
 [<ffffffff81007090>] syscall_return_slowpath arch/x86/entry/common.c:348 [inline]
 [<ffffffff81007090>] do_syscall_32_irqs_on arch/x86/entry/common.c:398 [inline]
 [<ffffffff81007090>] do_fast_syscall_32+0x620/0x8b0 arch/x86/entry/common.c:459
 [<ffffffff838c31aa>] sysenter_flags_fixed+0xd/0x17

Allocated by task 22716:
 [<ffffffff81033e46>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814f88d3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814f8bb7>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814f8bb7>] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814f52d4>] __kmalloc+0x124/0x310 mm/slub.c:3613
 [<ffffffff82f246a4>] kmalloc include/linux/slab.h:481 [inline]
 [<ffffffff82f246a4>] sk_prot_alloc+0x204/0x300 net/core/sock.c:1354
 [<ffffffff82f2a07a>] sk_alloc+0x3a/0x3a0 net/core/sock.c:1419
 [<ffffffff835a2713>] pppol2tp_create+0x33/0x1f0 net/l2tp/l2tp_ppp.c:551
 [<ffffffff828f0a76>] pppox_create+0xf6/0x200 drivers/net/ppp/pppox.c:121
 [<ffffffff82f1f500>] __sock_create+0x2f0/0x5f0 net/socket.c:1177
 [<ffffffff82f1fa30>] sock_create net/socket.c:1217 [inline]
 [<ffffffff82f1fa30>] SYSC_socket net/socket.c:1247 [inline]
 [<ffffffff82f1fa30>] SyS_socket+0xf0/0x1b0 net/socket.c:1227
 [<ffffffff81006d96>] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline]
 [<ffffffff81006d96>] do_fast_syscall_32+0x326/0x8b0 arch/x86/entry/common.c:459
 [<ffffffff838c31aa>] sysenter_flags_fixed+0xd/0x17

Freed by task 22706:
 [<ffffffff81033e46>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814f88d3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814f9202>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814f9202>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814f6704>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814f6704>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814f6704>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814f6704>] kfree+0xf4/0x310 mm/slub.c:3749
 [<ffffffff82f2e527>] sk_prot_free net/core/sock.c:1391 [inline]
 [<ffffffff82f2e527>] sk_destruct+0x407/0x4c0 net/core/sock.c:1472
 [<ffffffff82f2e62f>] __sk_free+0x4f/0x220 net/core/sock.c:1480
 [<ffffffff82f2e830>] sk_free+0x30/0x40 net/core/sock.c:1491
 [<ffffffff835a5ccf>] sock_put include/net/sock.h:1639 [inline]
 [<ffffffff835a5ccf>] pppol2tp_session_sock_put+0x5f/0x70 net/l2tp/l2tp_ppp.c:286
 [<ffffffff8359e54c>] l2tp_tunnel_closeall+0x23c/0x350 net/l2tp/l2tp_core.c:1277
 [<ffffffff8359f0db>] l2tp_udp_encap_destroy+0x8b/0xf0 net/l2tp/l2tp_core.c:1300
 [<ffffffff83491411>] udpv6_destroy_sock+0xb1/0xd0 net/ipv6/udp.c:1421
 [<ffffffff82f2e8ad>] sk_common_release+0x6d/0x300 net/core/sock.c:2680
 [<ffffffff834900c5>] udp_lib_close+0x15/0x20 include/net/udp.h:190
 [<ffffffff832f7b8f>] inet_release+0xff/0x1d0 net/ipv4/af_inet.c:435
 [<ffffffff8341a7f0>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:424
 [<ffffffff82f18fd6>] sock_release+0x96/0x1c0 net/socket.c:586
 [<ffffffff82f19116>] sock_close+0x16/0x20 net/socket.c:1037
 [<ffffffff81522e05>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff81523345>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118bd7f>] 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:252
 [<ffffffff81007090>] prepare_exit_to_usermode arch/x86/entry/common.c:283 [inline]
 [<ffffffff81007090>] syscall_return_slowpath arch/x86/entry/common.c:348 [inline]
 [<ffffffff81007090>] do_syscall_32_irqs_on arch/x86/entry/common.c:398 [inline]
 [<ffffffff81007090>] do_fast_syscall_32+0x620/0x8b0 arch/x86/entry/common.c:459
 [<ffffffff838c31aa>] sysenter_flags_fixed+0xd/0x17

The buggy address belongs to the object at ffff8801d8b20880
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 160 bytes inside of
 2048-byte region [ffff8801d8b20880, ffff8801d8b21080)
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: 3980 Comm: syz-executor3 Not tainted 4.4.139-g7ba5557 #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800bb271800 task.stack: ffff8801d68a8000
RIP: 0010:[<ffffffff81e70176>]  [<ffffffff81e70176>] __debug_check_no_obj_freed lib/debugobjects.c:689 [inline]
RIP: 0010:[<ffffffff81e70176>]  [<ffffffff81e70176>] debug_check_no_obj_freed+0x1a6/0x940 lib/debugobjects.c:726
RSP: 0000:ffff8801d68afa60  EFLAGS: 00010802
RAX: 0000000000000092 RBX: 8000000000004080 RCX: 0000000000000000
RDX: 1000000000000810 RSI: 0000000000000002 RDI: ffffea000762c818
RBP: ffff8801d68afb48 R08: ffff8801d68afae0 R09: dead000000000200
R10: 0000000000000001 R11: ffff8800bb271800 R12: 8000000000004080
R13: dffffc0000000000 R14: ffffffff85a7f2e8 R15: 00000001000f000f
FS:  0000000000000000(0000) GS:ffff8801db200000(0063) knlGS:0000000009958900
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00000000ffff8801 CR3: 00000001d8309000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8800bb2720d8 0000000100000000 ffffffff85a7f2e0 ffff8800b933c000
 ffff8800b933b420 ffffffff811bf562 0000000000000002 00000000000ecb40
 1ffff1003ad15f58 ffff8800b933b380 fffffbfff0b4fe5c ffff8800b933b000
Call Trace:
 [<ffffffff814f6458>] slab_free_hook mm/slub.c:1376 [inline]
 [<ffffffff814f6458>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814f6458>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814f6458>] kmem_cache_free+0x188/0x340 mm/slub.c:2881
 [<ffffffff81151fc1>] __sigqueue_free.part.28+0x51/0x60 kernel/signal.c:403
 [<ffffffff81153a7b>] __sigqueue_free kernel/signal.c:399 [inline]
 [<ffffffff81153a7b>] collect_signal kernel/signal.c:537 [inline]
 [<ffffffff81153a7b>] __dequeue_signal+0x31b/0x520 kernel/signal.c:558
 [<ffffffff81154160>] dequeue_signal+0x90/0x4b0 kernel/signal.c:576
 [<ffffffff8115e366>] get_signal+0x286/0x14b0 kernel/signal.c:2214
 [<ffffffff8100df8b>] do_signal+0x8b/0x1d30 arch/x86/kernel/signal.c:712
 [<ffffffff8100360a>] exit_to_usermode_loop+0x11a/0x160 arch/x86/entry/common.c:248
 [<ffffffff81006363>] prepare_exit_to_usermode+0xe3/0x100 arch/x86/entry/common.c:283
 [<ffffffff838c2408>] retint_user+0x8/0x3c
Code: 48 c7 c6 a0 27 99 85 4c 8b 24 3e 4d 85 e4 0f 84 f8 03 00 00 49 b9 00 02 00 00 00 00 ad de 31 f6 4c 8d 45 98 4c 89 e2 48 c1 ea 03 <42> 80 3c 2a 00 0f 85 e5 03 00 00 49 8d 7c 24 18 83 c6 01 49 8b 
RIP  [<ffffffff81e70176>] __debug_check_no_obj_freed lib/debugobjects.c:689 [inline]
RIP  [<ffffffff81e70176>] debug_check_no_obj_freed+0x1a6/0x940 lib/debugobjects.c:726
 RSP <ffff8801d68afa60>
---[ end trace 7b39d717b6e20794 ]---