netlink: 7 bytes leftover after parsing attributes in process `syz-executor2'.
==================================================================
BUG: KASAN: use-after-free in pppol2tp_session_destruct+0xee/0x110 net/l2tp/l2tp_ppp.c:476
Read of size 4 at addr ffff8800b196d680 by task syz-executor6/10731

CPU: 1 PID: 10731 Comm: syz-executor6 Not tainted 4.4.115-g0e9bcc1 #12
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 24acf5e869bcb5e1 ffff8800adcafc20 ffffffff81d03dad
 ffffea0002c65b00 ffff8800b196d680 0000000000000000 ffff8800b196d680
 ffffffff82de7c10 ffff8800adcafc58 ffffffff814fe1e3 ffff8800b196d680
Call Trace:
 [<ffffffff81d03dad>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d03dad>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff814fe1e3>] print_address_description+0x73/0x260 mm/kasan/report.c:252
 [<ffffffff814fe6f5>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff814fe6f5>] kasan_report+0x285/0x370 mm/kasan/report.c:408
 [<ffffffff814fe834>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428
 [<ffffffff83464b1e>] pppol2tp_session_destruct+0xee/0x110 net/l2tp/l2tp_ppp.c:476
 [<ffffffff82dfcb1a>] sk_destruct+0x4a/0x4c0 net/core/sock.c:1447
 [<ffffffff82dfcfe7>] __sk_free+0x57/0x230 net/core/sock.c:1480
 [<ffffffff82dfd1f0>] sk_free+0x30/0x40 net/core/sock.c:1491
 [<ffffffff834659da>] sock_put include/net/sock.h:1639 [inline]
 [<ffffffff834659da>] pppol2tp_release+0x27a/0x310 net/l2tp/l2tp_ppp.c:518
 [<ffffffff82de7abd>] sock_release+0x8d/0x1e0 net/socket.c:586
 [<ffffffff82de7c26>] sock_close+0x16/0x20 net/socket.c:1037
 [<ffffffff815236a3>] __fput+0x233/0x6d0 fs/file_table.c:208
 [<ffffffff81523bc5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118b9e4>] 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:251
 [<ffffffff81007067>] prepare_exit_to_usermode arch/x86/entry/common.c:282 [inline]
 [<ffffffff81007067>] syscall_return_slowpath arch/x86/entry/common.c:347 [inline]
 [<ffffffff81007067>] do_syscall_32_irqs_on arch/x86/entry/common.c:396 [inline]
 [<ffffffff81007067>] do_fast_syscall_32+0x607/0x890 arch/x86/entry/common.c:457
 [<ffffffff83775eaa>] sysenter_flags_fixed+0xd/0x17

Allocated by task 10731:
 [<ffffffff81035de6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fd253>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fd51d>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fd51d>] kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814f9804>] __kmalloc+0x124/0x320 mm/slub.c:3613
 [<ffffffff8345e7d9>] kmalloc include/linux/slab.h:481 [inline]
 [<ffffffff8345e7d9>] kzalloc include/linux/slab.h:620 [inline]
 [<ffffffff8345e7d9>] l2tp_session_create+0x39/0x10f0 net/l2tp/l2tp_core.c:1744
 [<ffffffff83462e6c>] pppol2tp_connect+0x10fc/0x1930 net/l2tp/l2tp_ppp.c:718
 [<ffffffff82dec476>] SYSC_connect+0x1b6/0x310 net/socket.c:1557
 [<ffffffff82deece4>] SyS_connect+0x24/0x30 net/socket.c:1538
 [<ffffffff81006d74>] do_syscall_32_irqs_on arch/x86/entry/common.c:390 [inline]
 [<ffffffff81006d74>] do_fast_syscall_32+0x314/0x890 arch/x86/entry/common.c:457
 [<ffffffff83775eaa>] sysenter_flags_fixed+0xd/0x17

Freed by task 10732:
 [<ffffffff81035de6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fd253>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fdb72>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fdb72>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814fa60c>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814fa60c>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814fa60c>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814fa60c>] kfree+0xfc/0x300 mm/slub.c:3749
 [<ffffffff8345ad60>] l2tp_session_free+0x170/0x200 net/l2tp/l2tp_core.c:1672
 [<ffffffff8345d611>] l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:293 [inline]
 [<ffffffff8345d611>] l2tp_tunnel_closeall+0x2d1/0x3b0 net/l2tp/l2tp_core.c:1279
 [<ffffffff8345e17b>] l2tp_udp_encap_destroy+0x8b/0xf0 net/l2tp/l2tp_core.c:1300
 [<ffffffff8336c641>] udpv6_destroy_sock+0xb1/0xd0 net/ipv6/udp.c:1421
 [<ffffffff82dfebbb>] sk_common_release+0x6b/0x300 net/core/sock.c:2680
 [<ffffffff8336b5f5>] udp_lib_close+0x15/0x20 include/net/udp.h:190
 [<ffffffff831cf2aa>] inet_release+0xfa/0x1d0 net/ipv4/af_inet.c:435
 [<ffffffff832f4eb0>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:424
 [<ffffffff82de7abd>] sock_release+0x8d/0x1e0 net/socket.c:586
 [<ffffffff82de7c26>] sock_close+0x16/0x20 net/socket.c:1037
 [<ffffffff815236a3>] __fput+0x233/0x6d0 fs/file_table.c:208
 [<ffffffff81523bc5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118b9e4>] 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:251
 [<ffffffff81007067>] prepare_exit_to_usermode arch/x86/entry/common.c:282 [inline]
 [<ffffffff81007067>] syscall_return_slowpath arch/x86/entry/common.c:347 [inline]
 [<ffffffff81007067>] do_syscall_32_irqs_on arch/x86/entry/common.c:396 [inline]
 [<ffffffff81007067>] do_fast_syscall_32+0x607/0x890 arch/x86/entry/common.c:457
 [<ffffffff83775eaa>] sysenter_flags_fixed+0xd/0x17

The buggy address belongs to the object at ffff8800b196d680
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 512-byte region [ffff8800b196d680, ffff8800b196d880)
The buggy address belongs to the page:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000061
IP: [<ffffffff838a8e6b>] str__compaction__trace_system_name+0x56b/0xfa0
PGD 80000001cc156067 PUD 1d0c2b067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.115-g0e9bcc1 #12
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffffffff84217840 task.stack: ffffffff84200000
RIP: 0010:[<ffffffff838a8e6b>]  [<ffffffff838a8e6b>] str__compaction__trace_system_name+0x56b/0xfa0
RSP: 0018:ffff8801db207d18  EFLAGS: 00010206
RAX: ffffffff838a8e60 RBX: ffff8801db207d68 RCX: ffffffff812a0eeb
RDX: 0000000000000100 RSI: ffffffff847ebc38 RDI: ffffffff812a0efb
RBP: ffff8801db207df0 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff838443e0 R11: 1ffff1003b640f70 R12: 1ffff1003b640fa9
R13: ffff8800ab587b50 R14: 0000000000000101 R15: ffff8801db207df0
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000061 CR3: 00000001cc328000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff838a8e60 ffffffff812a0e4c 0000000000000000 ffffffff842c35a0
 0000000000000000 ffffffff838a8e60 0000000041b58ab3 ffffffff83faa3d1
 ffffffff812a0d70 ffffffff812a2952 0000000000000000 0000000000000000
Call Trace:
 <IRQ> 
 [<ffffffff812a2e54>] __run_timers kernel/time/timer.c:1261 [inline]
 [<ffffffff812a2e54>] run_timer_softirq+0x604/0xbb0 kernel/time/timer.c:1444
 [<ffffffff83777a17>] __do_softirq+0x227/0xa38 kernel/softirq.c:273
 [<ffffffff8113db09>] invoke_softirq kernel/softirq.c:350 [inline]
 [<ffffffff8113db09>] irq_exit+0x119/0x140 kernel/softirq.c:391
 [<ffffffff8377717b>] exiting_irq arch/x86/include/asm/apic.h:653 [inline]
 [<ffffffff8377717b>] smp_apic_timer_interrupt+0x7b/0xa0 arch/x86/kernel/apic/apic.c:926
 [<ffffffff837760d0>] apic_timer_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:737
 <EOI> 
 [<ffffffff81027ed5>] arch_safe_halt arch/x86/include/asm/paravirt.h:117 [inline]
 [<ffffffff81027ed5>] default_idle+0x55/0x3c0 arch/x86/kernel/process.c:290
 [<ffffffff8102944a>] 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
 [<ffffffff83761459>] rest_init+0x189/0x190 init/main.c:410
 [<ffffffff84821811>] start_kernel+0x6b9/0x6ee init/main.c:682
 [<ffffffff84820312>] x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:196
 [<ffffffff84820454>] x86_64_start_kernel+0x140/0x163 arch/x86/kernel/head64.c:185
Code: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 56 4d 5f 42 55 47 5f 4f 4e 5f 50 <41> 47 45 28 50 61 67 65 53 6c 61 62 28 70 61 67 65 29 29 00 00 
RIP  [<ffffffff838a8e6b>] str__compaction__trace_system_name+0x56b/0xfa0
 RSP <ffff8801db207d18>
CR2: 0000000000000061
---[ end trace cc641c44a3f3e4d2 ]---