==================================================================
BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830
Read of size 4 at addr ffff8801d002d900 by task syz-executor5/11056

CPU: 0 PID: 11056 Comm: syz-executor5 Not tainted 4.4.152-ge5c5f1f #89
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 0db97b7b2f1ab35c ffff8801c0dc7a78 ffffffff81e15fed
 ffffea0007400b00 ffff8801d002d900 0000000000000000 ffff8801d002d900
 0000000000000000 ffff8801c0dc7ab0 ffffffff8151b489 ffff8801d002d900
Call Trace:
 [<ffffffff81e15fed>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e15fed>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff8151b489>] print_address_description+0x6c/0x216 mm/kasan/report.c:252
 [<ffffffff8151b7a8>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff8151b7a8>] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408
 [<ffffffff814fe714>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428
 [<ffffffff835a4b64>] l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830
 [<ffffffff835b166f>] pppol2tp_release+0x1ff/0x310 net/l2tp/l2tp_ppp.c:509
 [<ffffffff82f210c9>] __sock_release+0xd9/0x260 net/socket.c:592
 [<ffffffff82f21269>] sock_close+0x19/0x20 net/socket.c:1050
 [<ffffffff81528875>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff81528db5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118ee4f>] task_work_run+0x10f/0x190 kernel/task_work.c:115
 [<ffffffff81162290>] get_signal+0x1190/0x14b0 kernel/signal.c:2151
 [<ffffffff8100df4b>] do_signal+0x8b/0x1d30 arch/x86/kernel/signal.c:712
 [<ffffffff8100360a>] exit_to_usermode_loop+0x11a/0x160 arch/x86/entry/common.c:249
 [<ffffffff81006535>] prepare_exit_to_usermode arch/x86/entry/common.c:284 [inline]
 [<ffffffff81006535>] syscall_return_slowpath+0x1b5/0x1f0 arch/x86/entry/common.c:349
 [<ffffffff838cc6f5>] int_ret_from_sys_call+0x25/0xa3

Allocated by task 11039:
 [<ffffffff81034676>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fd7d3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fdab7>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fdab7>] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814fa1f4>] __kmalloc+0x124/0x310 mm/slub.c:3613
 [<ffffffff835a9f79>] kmalloc include/linux/slab.h:481 [inline]
 [<ffffffff835a9f79>] kzalloc include/linux/slab.h:620 [inline]
 [<ffffffff835a9f79>] l2tp_session_create+0x39/0x1030 net/l2tp/l2tp_core.c:1748
 [<ffffffff835aec80>] pppol2tp_connect+0x10f0/0x1910 net/l2tp/l2tp_ppp.c:725
 [<ffffffff82f27bf8>] SYSC_connect+0x1b8/0x300 net/socket.c:1570
 [<ffffffff82f2a544>] SyS_connect+0x24/0x30 net/socket.c:1551
 [<ffffffff838cc565>] entry_SYSCALL_64_fastpath+0x22/0x9e

Freed by task 11039:
 [<ffffffff81034676>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fd7d3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fe102>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fe102>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814fb664>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814fb664>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814fb664>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814fb664>] kfree+0xf4/0x310 mm/slub.c:3749
 [<ffffffff835a6ee0>] l2tp_session_free+0x170/0x200 net/l2tp/l2tp_core.c:1676
 [<ffffffff835a9299>] l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:293 [inline]
 [<ffffffff835a9299>] l2tp_tunnel_closeall+0x2b9/0x350 net/l2tp/l2tp_core.c:1279
 [<ffffffff835a9dab>] l2tp_udp_encap_destroy+0x8b/0xf0 net/l2tp/l2tp_core.c:1300
 [<ffffffff8349bc11>] udpv6_destroy_sock+0xb1/0xd0 net/ipv6/udp.c:1421
 [<ffffffff82f38add>] sk_common_release+0x6d/0x300 net/core/sock.c:2680
 [<ffffffff8349a8c5>] udp_lib_close+0x15/0x20 include/net/udp.h:190
 [<ffffffff8330244f>] inet_release+0xff/0x1d0 net/ipv4/af_inet.c:435
 [<ffffffff83424ec0>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:424
 [<ffffffff82f210c9>] __sock_release+0xd9/0x260 net/socket.c:592
 [<ffffffff82f21269>] sock_close+0x19/0x20 net/socket.c:1050
 [<ffffffff81528875>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff81528db5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118ee4f>] 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
 [<ffffffff838cc6f5>] int_ret_from_sys_call+0x25/0xa3

The buggy address belongs to the object at ffff8801d002d900
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 512-byte region [ffff8801d002d900, ffff8801d002db00)
The buggy address belongs to the page:
BUG: unable to handle kernel paging request at fffffffe04b83e80
IP: [<ffffffff81227d85>] cpuacct_charge+0x155/0x380 kernel/sched/cpuacct.c:247
PGD 440f067 PUD 0 
Oops: 0000 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 3912 Comm: syz-executor5 Not tainted 4.4.152-ge5c5f1f #89
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d9479800 task.stack: ffff8800a38c0000
RIP: 0010:[<ffffffff81227d85>]  [<ffffffff81227d85>] cpuacct_charge+0x155/0x380 kernel/sched/cpuacct.c:247
RSP: 0018:ffff8801db307a48  EFLAGS: 00010046
RAX: 1ffffffff089521f RBX: 00000000000185a8 RCX: ffffffff84a16680
RDX: fffffbffc09707d0 RSI: fffffffe04b83e80 RDI: ffffffff844a90f8
RBP: ffff8801db307a88 R08: ffff8801d947a1a0 R09: 0000000000000001
R10: 0000000000000001 R11: ffff8801d9479800 R12: ffffffff844a9020
R13: dffffc0000000000 R14: 0000000008580f5b R15: ffffffffd002db00
FS:  0000000001dee940(0063) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffffe04b83e80 CR3: 00000000a384a000 CR4: 00000000001606f0
Stack:
 ffffffff81227c90 0000000000000046 0000000000000003 ffff8801d7fb8060
 ffff8801d7fb8000 0000000008580f5b ffff8801d7fb80b0 0000000000000000
 ffff8801db307ad0 ffffffff811dc309 ffffffff810cdee3 ffff8801db307ab0
Call Trace:
 <IRQ> 
 [<ffffffff811dc309>] update_curr+0x2c9/0x6d0 kernel/sched/fair.c:882
 [<ffffffff811e692a>] dequeue_entity kernel/sched/fair.c:3588 [inline]
 [<ffffffff811e692a>] dequeue_task_fair+0x1aa/0xa90 kernel/sched/fair.c:4775
 [<ffffffff811bec15>] dequeue_task kernel/sched/core.c:866 [inline]
 [<ffffffff811bec15>] deactivate_task+0xf5/0x2e0 kernel/sched/core.c:882
 [<ffffffff811d8f55>] detach_task+0x85/0x370 kernel/sched/fair.c:7552
 [<ffffffff811fd334>] detach_tasks kernel/sched/fair.c:7642 [inline]
 [<ffffffff811fd334>] load_balance+0xc44/0x2d80 kernel/sched/fair.c:9063
 [<ffffffff81201aee>] rebalance_domains+0x6be/0xbc0 kernel/sched/fair.c:9681
 [<ffffffff812022ef>] run_rebalance_domains+0x2ff/0x480 kernel/sched/fair.c:9897
 [<ffffffff838cfa7c>] __do_softirq+0x22c/0xa1a kernel/softirq.c:273
 [<ffffffff811428cd>] invoke_softirq kernel/softirq.c:350 [inline]
 [<ffffffff811428cd>] irq_exit+0x10d/0x140 kernel/softirq.c:391
 [<ffffffff838cf1e1>] exiting_irq arch/x86/include/asm/apic.h:652 [inline]
 [<ffffffff838cf1e1>] smp_apic_timer_interrupt+0x81/0xa0 arch/x86/kernel/apic/apic.c:926
 [<ffffffff838ce120>] apic_timer_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:741
 <EOI> 
 [<ffffffff81c59fed>] spin_unlock_irqrestore include/linux/spinlock.h:362 [inline]
 [<ffffffff81c59fed>] avc_reclaim_node security/selinux/avc.c:543 [inline]
 [<ffffffff81c59fed>] avc_alloc_node+0x28d/0x3d0 security/selinux/avc.c:561
 [<ffffffff81c5ac38>] avc_insert security/selinux/avc.c:672 [inline]
 [<ffffffff81c5ac38>] avc_compute_av+0x178/0x610 security/selinux/avc.c:978
 [<ffffffff81c5ccde>] avc_has_perm_noaudit security/selinux/avc.c:1114 [inline]
 [<ffffffff81c5ccde>] avc_has_perm+0x36e/0x4f0 security/selinux/avc.c:1148
 [<ffffffff81c7093c>] task_has_perm+0x1fc/0x330 security/selinux/hooks.c:1525
 [<ffffffff81c70a93>] selinux_task_wait+0x23/0x30 security/selinux/hooks.c:3763
 [<ffffffff81c55c83>] security_task_wait+0x73/0xb0 security/security.c:986
 [<ffffffff8113a258>] wait_consider_task+0x298/0x35f0 kernel/exit.c:1326
 [<ffffffff8113d914>] do_wait_thread kernel/exit.c:1439 [inline]
 [<ffffffff8113d914>] do_wait+0x364/0xa30 kernel/exit.c:1510
 [<ffffffff8113e88b>] SYSC_wait4 kernel/exit.c:1641 [inline]
 [<ffffffff8113e88b>] SyS_wait4+0x12b/0x1f0 kernel/exit.c:1606
 [<ffffffff838cc565>] entry_SYSCALL_64_fastpath+0x22/0x9e
Code: 49 8d bc 24 d8 00 00 00 48 89 f8 48 c1 e8 03 42 80 3c 28 00 0f 85 c4 01 00 00 49 8b 9c 24 d8 00 00 00 80 3a 00 0f 85 8f 01 00 00 <4a> 03 1c f9 48 89 d8 48 c1 e8 03 42 80 3c 28 00 0f 85 be 01 00 
RIP  [<ffffffff81227d85>] cpuacct_charge+0x155/0x380 kernel/sched/cpuacct.c:247
 RSP <ffff8801db307a48>
CR2: fffffffe04b83e80
---[ end trace a78542e93ddbd9e4 ]---