==================================================================
BUG: KASAN: use-after-free in pppol2tp_session_destruct+0xee/0x110 net/l2tp/l2tp_ppp.c:476
Read of size 4 at addr ffff8800b3c8a000 by task syzkaller128483/3322

CPU: 0 PID: 3322 Comm: syzkaller128483 Not tainted 4.4.112-g3fc4284 #25
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 3ab0afdfc3b7218a ffff8800b47a7c28 ffffffff81d054ed
 ffffea0002cf2280 ffff8800b3c8a000 0000000000000000 ffff8800b3c8a000
 ffffffff82dea4d0 ffff8800b47a7c60 ffffffff814fd953 ffff8800b3c8a000
Call Trace:
 [<ffffffff81d054ed>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d054ed>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff814fd953>] print_address_description+0x73/0x260 mm/kasan/report.c:252
 [<ffffffff814fde65>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff814fde65>] kasan_report+0x285/0x370 mm/kasan/report.c:408
 [<ffffffff814fdfa4>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428
 [<ffffffff8346680e>] pppol2tp_session_destruct+0xee/0x110 net/l2tp/l2tp_ppp.c:476
 [<ffffffff82dff42a>] sk_destruct+0x4a/0x4c0 net/core/sock.c:1447
 [<ffffffff82dff8f7>] __sk_free+0x57/0x230 net/core/sock.c:1480
 [<ffffffff82dffb00>] sk_free+0x30/0x40 net/core/sock.c:1491
 [<ffffffff834676ca>] sock_put include/net/sock.h:1639 [inline]
 [<ffffffff834676ca>] pppol2tp_release+0x27a/0x310 net/l2tp/l2tp_ppp.c:518
 [<ffffffff82dea37d>] sock_release+0x8d/0x1e0 net/socket.c:586
 [<ffffffff82dea4e6>] sock_close+0x16/0x20 net/socket.c:1037
 [<ffffffff81522f93>] __fput+0x233/0x6d0 fs/file_table.c:208
 [<ffffffff815234b5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118bb54>] task_work_run+0x104/0x180 kernel/task_work.c:115
 [<ffffffff81003625>] tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 [<ffffffff81003625>] exit_to_usermode_loop+0x145/0x170 arch/x86/entry/common.c:251
 [<ffffffff81007077>] prepare_exit_to_usermode arch/x86/entry/common.c:282 [inline]
 [<ffffffff81007077>] syscall_return_slowpath arch/x86/entry/common.c:347 [inline]
 [<ffffffff81007077>] do_syscall_32_irqs_on arch/x86/entry/common.c:396 [inline]
 [<ffffffff81007077>] do_fast_syscall_32+0x607/0x890 arch/x86/entry/common.c:457
 [<ffffffff83777b6a>] sysenter_flags_fixed+0xd/0x17

Allocated by task 3321:
 [<ffffffff81035df6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fc9c3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fcc8d>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fcc8d>] kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814f8f64>] __kmalloc+0x124/0x320 mm/slub.c:3613
 [<ffffffff834604c9>] kmalloc include/linux/slab.h:481 [inline]
 [<ffffffff834604c9>] kzalloc include/linux/slab.h:620 [inline]
 [<ffffffff834604c9>] l2tp_session_create+0x39/0x10f0 net/l2tp/l2tp_core.c:1744
 [<ffffffff83464b5c>] pppol2tp_connect+0x10fc/0x1930 net/l2tp/l2tp_ppp.c:718
 [<ffffffff82deed36>] SYSC_connect+0x1b6/0x310 net/socket.c:1557
 [<ffffffff82df15a4>] SyS_connect+0x24/0x30 net/socket.c:1538
 [<ffffffff81006d84>] do_syscall_32_irqs_on arch/x86/entry/common.c:390 [inline]
 [<ffffffff81006d84>] do_fast_syscall_32+0x314/0x890 arch/x86/entry/common.c:457
 [<ffffffff83777b6a>] sysenter_flags_fixed+0xd/0x17

Freed by task 3321:
 [<ffffffff81035df6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fc9c3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fd2e2>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fd2e2>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814f9d6c>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814f9d6c>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814f9d6c>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814f9d6c>] kfree+0xfc/0x300 mm/slub.c:3749
 [<ffffffff8345ca50>] l2tp_session_free+0x170/0x200 net/l2tp/l2tp_core.c:1672
 [<ffffffff8345f301>] l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:293 [inline]
 [<ffffffff8345f301>] l2tp_tunnel_closeall+0x2d1/0x3b0 net/l2tp/l2tp_core.c:1279
 [<ffffffff8345fe6b>] l2tp_udp_encap_destroy+0x8b/0xf0 net/l2tp/l2tp_core.c:1300
 [<ffffffff8336e6b1>] udpv6_destroy_sock+0xb1/0xd0 net/ipv6/udp.c:1421
 [<ffffffff82e014cb>] sk_common_release+0x6b/0x300 net/core/sock.c:2680
 [<ffffffff8336d665>] udp_lib_close+0x15/0x20 include/net/udp.h:190
 [<ffffffff831d16da>] inet_release+0xfa/0x1d0 net/ipv4/af_inet.c:435
 [<ffffffff832f6f90>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:424
 [<ffffffff82dea37d>] sock_release+0x8d/0x1e0 net/socket.c:586
 [<ffffffff82dea4e6>] sock_close+0x16/0x20 net/socket.c:1037
 [<ffffffff81522f93>] __fput+0x233/0x6d0 fs/file_table.c:208
 [<ffffffff815234b5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118bb54>] task_work_run+0x104/0x180 kernel/task_work.c:115
 [<ffffffff81003625>] tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 [<ffffffff81003625>] exit_to_usermode_loop+0x145/0x170 arch/x86/entry/common.c:251
 [<ffffffff81007077>] prepare_exit_to_usermode arch/x86/entry/common.c:282 [inline]
 [<ffffffff81007077>] syscall_return_slowpath arch/x86/entry/common.c:347 [inline]
 [<ffffffff81007077>] do_syscall_32_irqs_on arch/x86/entry/common.c:396 [inline]
 [<ffffffff81007077>] do_fast_syscall_32+0x607/0x890 arch/x86/entry/common.c:457
 [<ffffffff83777b6a>] sysenter_flags_fixed+0xd/0x17

The buggy address belongs to the object at ffff8800b3c8a000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 512-byte region [ffff8800b3c8a000, ffff8800b3c8a200)
The buggy address belongs to the page:
BUG: unable to handle kernel paging request at fffffffb8ec69a48
IP: [<ffffffff8122a565>] cpuacct_charge+0x155/0x390 kernel/sched/cpuacct.c:247
PGD 420f067 PUD 0 
Thread overran stack, or stack corrupted
Oops: 0000 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 3321 Comm: syzkaller128483 Not tainted 4.4.112-g3fc4284 #25
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d1998000 task.stack: ffff8800b4030000
RIP: 0010:[<ffffffff8122a565>]  [<ffffffff8122a565>] cpuacct_charge+0x155/0x390 kernel/sched/cpuacct.c:247
RSP: 0018:ffff8801db307bc8  EFLAGS: 00010046
RAX: 1ffffffff0854dff RBX: 0000000000018528 RCX: ffffffff847ea4c0
RDX: fffffbff71d8d349 RSI: fffffffb8ec69a48 RDI: ffffffff842a6ff8
RBP: ffff8801db307c10 R08: 0000000000000001 R09: 0000000000000001
R10: 0000000000000000 R11: 1ffff1003b660f44 R12: ffffffff842a6f20
R13: dffffc0000000000 R14: 0000000000989249 R15: ffffffff8148feb1
FS:  0000000000000000(0000) GS:ffff8801db300000(0063) knlGS:00000000f77b0b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: fffffffb8ec69a48 CR3: 00000000b4eb0000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8122a470 ffff8801db307bf8 0000000000000046 0000000000000003
 ffff8801d1998060 ffffffff83843ba0 0000000000989249 ffff8801d19980b0
 ffff8801d1998000 ffff8801db307c60 ffffffff811dc087 ffff8801db307c60
Call Trace:
 <IRQ> 
 [<ffffffff811dc087>] update_curr+0x2c7/0x6c0 kernel/sched/fair.c:882
 [<ffffffff811e904b>] entity_tick kernel/sched/fair.c:3799 [inline]
 [<ffffffff811e904b>] task_tick_fair+0x7b/0x2a40 kernel/sched/fair.c:9951
 [<ffffffff811c82fc>] scheduler_tick+0xdc/0x300 kernel/sched/core.c:3001
 [<ffffffff812aa19c>] update_process_times+0x5c/0x70 kernel/time/timer.c:1425
 [<ffffffff812d47a5>] tick_sched_handle.isra.16+0x55/0xf0 kernel/time/tick-sched.c:151
 [<ffffffff812d60c2>] tick_sched_timer+0x72/0x120 kernel/time/tick-sched.c:1097
 [<ffffffff812ac976>] __run_hrtimer kernel/time/hrtimer.c:1253 [inline]
 [<ffffffff812ac976>] __hrtimer_run_queues+0x306/0xfe0 kernel/time/hrtimer.c:1317
 [<ffffffff812aee46>] hrtimer_interrupt+0x1a6/0x440 kernel/time/hrtimer.c:1351
 [<ffffffff810b0dda>] local_apic_timer_interrupt+0x6a/0xb0 arch/x86/kernel/apic/apic.c:901
 [<ffffffff83778e36>] smp_apic_timer_interrupt+0x76/0xa0 arch/x86/kernel/apic/apic.c:925
 [<ffffffff83777d90>] apic_timer_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:725
 <EOI> 
 [<ffffffff812e259e>] rep_nop arch/x86/include/asm/processor.h:562 [inline]
 [<ffffffff812e259e>] cpu_relax arch/x86/include/asm/processor.h:567 [inline]
 [<ffffffff812e259e>] csd_lock_wait kernel/smp.c:111 [inline]
 [<ffffffff812e259e>] smp_call_function_single+0x13e/0x3b0 kernel/smp.c:303
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 [<ffffffff8148feb1>] dump_page mm/debug.c:105 [inline]
 [<ffffffff8148feb1>] page_mapcount include/linux/mm.h:460 [inline]
 [<ffffffff8148feb1>] dump_page_badflags+0x191/0x250 mm/debug.c:85
Code: 49 8d bc 24 d8 00 00 00 48 89 f8 48 c1 e8 03 42 80 3c 28 00 0f 85 9e 01 00 00 49 8b 9c 24 d8 00 00 00 80 3a 00 0f 85 0a 02 00 00 <4a> 03 1c f9 48 89 d8 48 c1 e8 03 42 80 3c 28 00 0f 85 cf 01 00 
RIP  [<ffffffff8122a565>] cpuacct_charge+0x155/0x390 kernel/sched/cpuacct.c:247
 RSP <ffff8801db307bc8>
CR2: fffffffb8ec69a48
---[ end trace a2780ac4d476887e ]---