==================================================================
BUG: KASAN: use-after-free in __lock_acquire+0x387e/0x4b50 kernel/locking/lockdep.c:3092
Read of size 8 at addr ffff8800b2be1a20 by task syz-executor7/16563

CPU: 0 PID: 16563 Comm: syz-executor7 Not tainted 4.4.120-gd63fdf6 #29
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 f355ebc445094b08 ffff8800b2af7620 ffffffff81d0408d
 ffffea0002caf800 ffff8800b2be1a20 0000000000000000 ffff8800b2be1a20
 0000000000000000 ffff8800b2af7658 ffffffff814fe143 ffff8800b2be1a20
Call Trace:
 [<ffffffff81d0408d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d0408d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff814fe143>] print_address_description+0x73/0x260 mm/kasan/report.c:252
 [<ffffffff814fe655>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff814fe655>] kasan_report+0x285/0x370 mm/kasan/report.c:408
 [<ffffffff814fe7b4>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
 [<ffffffff8123ac8e>] __lock_acquire+0x387e/0x4b50 kernel/locking/lockdep.c:3092
 [<ffffffff8123d7ce>] lock_acquire+0x15e/0x460 kernel/locking/lockdep.c:3592
 [<ffffffff83772c2a>] __raw_spin_lock_bh include/linux/spinlock_api_smp.h:137 [inline]
 [<ffffffff83772c2a>] _raw_spin_lock_bh+0x3a/0x50 kernel/locking/spinlock.c:175
 [<ffffffff82df42e3>] spin_lock_bh include/linux/spinlock.h:307 [inline]
 [<ffffffff82df42e3>] lock_sock_nested+0x43/0x120 net/core/sock.c:2451
 [<ffffffff83465e90>] lock_sock include/net/sock.h:1493 [inline]
 [<ffffffff83465e90>] pppol2tp_release+0x50/0x310 net/l2tp/l2tp_ppp.c:493
 [<ffffffff82de7bdd>] sock_release+0x8d/0x1e0 net/socket.c:586
 [<ffffffff82de7d46>] sock_close+0x16/0x20 net/socket.c:1037
 [<ffffffff81523603>] __fput+0x233/0x6d0 fs/file_table.c:208
 [<ffffffff81523b25>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118b984>] task_work_run+0x104/0x180 kernel/task_work.c:115
 [<ffffffff81132f2a>] exit_task_work include/linux/task_work.h:21 [inline]
 [<ffffffff81132f2a>] do_exit+0x82a/0x2a10 kernel/exit.c:755
 [<ffffffff811393c8>] do_group_exit+0x108/0x320 kernel/exit.c:885
 [<ffffffff8115c822>] get_signal+0x4f2/0x1550 kernel/signal.c:2317
 [<ffffffff8100e7fb>] do_signal+0x8b/0x1d40 arch/x86/kernel/signal.c:712
 [<ffffffff810035fa>] exit_to_usermode_loop+0x11a/0x160 arch/x86/entry/common.c:248
 [<ffffffff81007084>] prepare_exit_to_usermode arch/x86/entry/common.c:283 [inline]
 [<ffffffff81007084>] syscall_return_slowpath arch/x86/entry/common.c:348 [inline]
 [<ffffffff81007084>] do_syscall_32_irqs_on arch/x86/entry/common.c:398 [inline]
 [<ffffffff81007084>] do_fast_syscall_32+0x614/0x8a0 arch/x86/entry/common.c:459
 [<ffffffff837752ea>] sysenter_flags_fixed+0xd/0x17

Allocated by task 16557:
 [<ffffffff81035d96>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fd1b3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fd47d>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fd47d>] kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814f9764>] __kmalloc+0x124/0x320 mm/slub.c:3613
 [<ffffffff82df30fc>] kmalloc include/linux/slab.h:481 [inline]
 [<ffffffff82df30fc>] sk_prot_alloc+0x18c/0x310 net/core/sock.c:1354
 [<ffffffff82df941a>] sk_alloc+0x3a/0x3a0 net/core/sock.c:1419
 [<ffffffff83461c73>] pppol2tp_create+0x33/0x1f0 net/l2tp/l2tp_ppp.c:551
 [<ffffffff827fde71>] pppox_create+0xf1/0x200 drivers/net/ppp/pppox.c:121
 [<ffffffff82dee04c>] __sock_create+0x3ac/0x640 net/socket.c:1177
 [<ffffffff82dee510>] sock_create net/socket.c:1217 [inline]
 [<ffffffff82dee510>] SYSC_socket net/socket.c:1247 [inline]
 [<ffffffff82dee510>] SyS_socket+0xf0/0x1b0 net/socket.c:1227
 [<ffffffff81006d91>] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline]
 [<ffffffff81006d91>] do_fast_syscall_32+0x321/0x8a0 arch/x86/entry/common.c:459
 [<ffffffff837752ea>] sysenter_flags_fixed+0xd/0x17

Freed by task 16563:
 [<ffffffff81035d96>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fd1b3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fdad2>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fdad2>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814fa56c>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814fa56c>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814fa56c>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814fa56c>] kfree+0xfc/0x300 mm/slub.c:3749
 [<ffffffff82dfcfe7>] sk_prot_free net/core/sock.c:1391 [inline]
 [<ffffffff82dfcfe7>] sk_destruct+0x3f7/0x4c0 net/core/sock.c:1472
 [<ffffffff82dfd107>] __sk_free+0x57/0x230 net/core/sock.c:1480
 [<ffffffff82dfd310>] sk_free+0x30/0x40 net/core/sock.c:1491
 [<ffffffff8346527f>] sock_put include/net/sock.h:1639 [inline]
 [<ffffffff8346527f>] pppol2tp_session_sock_put+0x5f/0x70 net/l2tp/l2tp_ppp.c:286
 [<ffffffff8345dc74>] l2tp_tunnel_closeall+0x254/0x3b0 net/l2tp/l2tp_core.c:1277
 [<ffffffff8345e85b>] l2tp_udp_encap_destroy+0x8b/0xf0 net/l2tp/l2tp_core.c:1300
 [<ffffffff831a4d88>] udp_destroy_sock+0x118/0x1a0 net/ipv4/udp.c:2048
 [<ffffffff82dfecdb>] sk_common_release+0x6b/0x300 net/core/sock.c:2680
 [<ffffffff831a1165>] udp_lib_close+0x15/0x20 include/net/udp.h:190
 [<ffffffff831cfdda>] inet_release+0xfa/0x1d0 net/ipv4/af_inet.c:435
 [<ffffffff82de7bdd>] sock_release+0x8d/0x1e0 net/socket.c:586
 [<ffffffff82de7d46>] sock_close+0x16/0x20 net/socket.c:1037
 [<ffffffff81523603>] __fput+0x233/0x6d0 fs/file_table.c:208
 [<ffffffff81523b25>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118b984>] task_work_run+0x104/0x180 kernel/task_work.c:115
 [<ffffffff8100361d>] tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 [<ffffffff8100361d>] exit_to_usermode_loop+0x13d/0x160 arch/x86/entry/common.c:252
 [<ffffffff81007084>] prepare_exit_to_usermode arch/x86/entry/common.c:283 [inline]
 [<ffffffff81007084>] syscall_return_slowpath arch/x86/entry/common.c:348 [inline]
 [<ffffffff81007084>] do_syscall_32_irqs_on arch/x86/entry/common.c:398 [inline]
 [<ffffffff81007084>] do_fast_syscall_32+0x614/0x8a0 arch/x86/entry/common.c:459
 [<ffffffff837752ea>] sysenter_flags_fixed+0xd/0x17

The buggy address belongs to the object at ffff8800b2be1980
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 160 bytes inside of
 2048-byte region [ffff8800b2be1980, ffff8800b2be2180)
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: 0 Comm: swapper/1 Not tainted 4.4.120-gd63fdf6 #29
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d9b49800 task.stack: ffff8801d9b58000
RIP: 0010:[<ffffffff81d66006>]  [<ffffffff81d66006>] lookup_object lib/debugobjects.c:120 [inline]
RIP: 0010:[<ffffffff81d66006>]  [<ffffffff81d66006>] debug_object_deactivate+0x1a6/0x3c0 lib/debugobjects.c:465
RSP: 0018:ffff8801db307d20  EFLAGS: 00010002
RAX: 0000000000000092 RBX: 4000000000004080 RCX: ffff8801cede7b50
RDX: 0800000000000813 RSI: ffffffff842c35a0 RDI: 4000000000004098
RBP: ffff8801db307df0 R08: 1ffff100154fd1ae R09: ffffffff85135d90
R10: 0000000000000001 R11: 1ffff1003b660f6a R12: 1ffff1003b660fa8
R13: 0000000000000003 R14: dffffc0000000000 R15: ffffffff8576af88
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000813b029 CR3: 00000001cf824000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801d9b49800 0000000000000000 ffffffff842c35a0 ffff8801cede7b50
 0000000041b58ab3 ffffffff83fce929 ffffffff81d65e60 0000000000000000
 ffffffff812a2e5c ffffffff00000000 ffffffff00000000 0000000000000000
Call Trace:
 <IRQ> 
 [<ffffffff812a2b86>] debug_timer_deactivate kernel/time/timer.c:618 [inline]
 [<ffffffff812a2b86>] debug_deactivate kernel/time/timer.c:670 [inline]
 [<ffffffff812a2b86>] detach_timer kernel/time/timer.c:716 [inline]
 [<ffffffff812a2b86>] detach_expired_timer kernel/time/timer.c:727 [inline]
 [<ffffffff812a2b86>] __run_timers kernel/time/timer.c:1253 [inline]
 [<ffffffff812a2b86>] run_timer_softirq+0x336/0xbb0 kernel/time/timer.c:1444
 [<ffffffff83776e57>] __do_softirq+0x227/0xa38 kernel/softirq.c:273
 [<ffffffff8113daa9>] invoke_softirq kernel/softirq.c:350 [inline]
 [<ffffffff8113daa9>] irq_exit+0x119/0x140 kernel/softirq.c:391
 [<ffffffff837765bb>] exiting_irq arch/x86/include/asm/apic.h:653 [inline]
 [<ffffffff837765bb>] smp_apic_timer_interrupt+0x7b/0xa0 arch/x86/kernel/apic/apic.c:926
 [<ffffffff83775510>] apic_timer_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:737
 <EOI> 
 [<ffffffff81027e85>] arch_safe_halt arch/x86/include/asm/paravirt.h:117 [inline]
 [<ffffffff81027e85>] default_idle+0x55/0x3c0 arch/x86/kernel/process.c:290
 [<ffffffff810293fa>] arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:281
 [<ffffffff81221468>] default_idle_call+0x48/0x70 kernel/sched/idle.c:93
 [<ffffffff81221b6d>] cpuidle_idle_call kernel/sched/idle.c:157 [inline]
 [<ffffffff81221b6d>] cpu_idle_loop kernel/sched/idle.c:253 [inline]
 [<ffffffff81221b6d>] cpu_startup_entry+0x5fd/0x8f0 kernel/sched/idle.c:301
 [<ffffffff810adc64>] start_secondary+0x304/0x3e0 arch/x86/kernel/smpboot.c:242
Code: eb 1a 48 89 da 48 c1 ea 03 42 80 3c 32 00 0f 85 86 01 00 00 48 8b 1b 48 85 db 74 7a 48 8d 7b 18 41 83 c5 01 48 89 fa 48 c1 ea 03 <42> 80 3c 32 00 0f 85 3c 01 00 00 48 3b 4b 18 75 c6 48 8d 7b 10 
RIP  [<ffffffff81d66006>] lookup_object lib/debugobjects.c:120 [inline]
RIP  [<ffffffff81d66006>] debug_object_deactivate+0x1a6/0x3c0 lib/debugobjects.c:465
 RSP <ffff8801db307d20>
---[ end trace 44608947267fa5cb ]---