random: sshd: uninitialized urandom read (32 bytes read, 37 bits of entropy available)
random: sshd: uninitialized urandom read (32 bytes read, 119 bits of entropy available)
random: nonblocking pool is initialized
IPVS: Creating netns size=2552 id=1
==================================================================
BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xe8/0x100 net/l2tp/l2tp_core.c:830
Read of size 4 at addr ffff8800b021d180 by task syzkaller749412/3720

CPU: 1 PID: 3720 Comm: syzkaller749412 Not tainted 4.4.125-g38f41ec #63
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 f9d31e187a220e50 ffff8800af49fcc0 ffffffff81d067bd
 ffffea0002c08700 ffff8800b021d180 0000000000000000 ffff8800b021d180
 ffffffff82ded950 ffff8800af49fcf8 ffffffff814fea83 ffff8800b021d180
Call Trace:
 [<ffffffff81d067bd>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d067bd>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff814fea83>] print_address_description+0x73/0x260 mm/kasan/report.c:252
 [<ffffffff814fef95>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff814fef95>] kasan_report+0x285/0x370 mm/kasan/report.c:408
 [<ffffffff814ff0d4>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428
 [<ffffffff8345ee78>] l2tp_session_queue_purge+0xe8/0x100 net/l2tp/l2tp_core.c:830
 [<ffffffff8346bf0f>] pppol2tp_release+0x1ff/0x310 net/l2tp/l2tp_ppp.c:509
 [<ffffffff82ded7fd>] sock_release+0x8d/0x1e0 net/socket.c:586
 [<ffffffff82ded966>] sock_close+0x16/0x20 net/socket.c:1037
 [<ffffffff81523f43>] __fput+0x233/0x6d0 fs/file_table.c:208
 [<ffffffff81524465>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118bd44>] 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
 [<ffffffff81006535>] prepare_exit_to_usermode arch/x86/entry/common.c:283 [inline]
 [<ffffffff81006535>] syscall_return_slowpath+0x1b5/0x1f0 arch/x86/entry/common.c:348
 [<ffffffff83779af5>] int_ret_from_sys_call+0x25/0xa3

Allocated by task 3717:
 [<ffffffff81035d76>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fdaf3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fddbd>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fddbd>] kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814fa0a4>] __kmalloc+0x124/0x320 mm/slub.c:3613
 [<ffffffff83464d89>] kmalloc include/linux/slab.h:481 [inline]
 [<ffffffff83464d89>] kzalloc include/linux/slab.h:620 [inline]
 [<ffffffff83464d89>] l2tp_session_create+0x39/0x10f0 net/l2tp/l2tp_core.c:1744
 [<ffffffff8346941c>] pppol2tp_connect+0x10fc/0x1930 net/l2tp/l2tp_ppp.c:718
 [<ffffffff82df21b6>] SYSC_connect+0x1b6/0x310 net/socket.c:1557
 [<ffffffff82df4a24>] SyS_connect+0x24/0x30 net/socket.c:1538
 [<ffffffff83779965>] entry_SYSCALL_64_fastpath+0x22/0x9e

Freed by task 3717:
 [<ffffffff81035d76>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fdaf3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fe412>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fe412>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814faeac>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814faeac>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814faeac>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814faeac>] kfree+0xfc/0x300 mm/slub.c:3749
 [<ffffffff83461310>] l2tp_session_free+0x170/0x200 net/l2tp/l2tp_core.c:1672
 [<ffffffff83463bc1>] l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:293 [inline]
 [<ffffffff83463bc1>] l2tp_tunnel_closeall+0x2d1/0x3b0 net/l2tp/l2tp_core.c:1279
 [<ffffffff8346472b>] l2tp_udp_encap_destroy+0x8b/0xf0 net/l2tp/l2tp_core.c:1300
 [<ffffffff833729c1>] udpv6_destroy_sock+0xb1/0xd0 net/ipv6/udp.c:1421
 [<ffffffff82e048fb>] sk_common_release+0x6b/0x300 net/core/sock.c:2680
 [<ffffffff83371975>] udp_lib_close+0x15/0x20 include/net/udp.h:190
 [<ffffffff831d5eba>] inet_release+0xfa/0x1d0 net/ipv4/af_inet.c:435
 [<ffffffff832fb320>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:424
 [<ffffffff82ded7fd>] sock_release+0x8d/0x1e0 net/socket.c:586
 [<ffffffff82ded966>] sock_close+0x16/0x20 net/socket.c:1037
 [<ffffffff81523f43>] __fput+0x233/0x6d0 fs/file_table.c:208
 [<ffffffff81524465>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118bd44>] 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
 [<ffffffff81006535>] prepare_exit_to_usermode arch/x86/entry/common.c:283 [inline]
 [<ffffffff81006535>] syscall_return_slowpath+0x1b5/0x1f0 arch/x86/entry/common.c:348
 [<ffffffff83779af5>] int_ret_from_sys_call+0x25/0xa3

The buggy address belongs to the object at ffff8800b021d180
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 512-byte region [ffff8800b021d180, ffff8800b021d380)
The buggy address belongs to the page:
kasan: CONFIG_KASAN_INLINE enabled[   44.074109] page:ffffea0002c08700 count:1 mapcount:-2146697203 mapping:          (null) index:0x0
flags: 0xffff8801db219c40(active|reserved|private|private_2|swapcache|mappedtodisk|uncached)
page dumped because: VM_BUG_ON_PAGE(PageSlab(page))
------------[ cut here ]------------
kernel BUG at include/linux/mm.h:460!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 3720 Comm: syzkaller749412 Not tainted 4.4.125-g38f41ec #63
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800afd5b000 task.stack: ffff8800af498000
RIP: 0010:[<ffffffff81491301>]  [<ffffffff81491301>] dump_page mm/debug.c:105 [inline]
RIP: 0010:[<ffffffff81491301>]  [<ffffffff81491301>] page_mapcount include/linux/mm.h:460 [inline]
RIP: 0010:[<ffffffff81491301>]  [<ffffffff81491301>] dump_page_badflags+0x191/0x250 mm/debug.c:85
RSP: 0018:ffff8800ae200030  EFLAGS: 00010082
RAX: ffff8800afd5b000 RBX: ffffea0002c08700 RCX: ffffffff814912dc
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8800afd5b8dc
RBP: ffff8800ae200060 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000002 R11: fffffbfff0ad9688 R12: 0000000000000000
R13: ffffffff838a91a0 R14: 0000000000000000 R15: 0000000000000000
FS:  00007faacd49c700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000205fafd2 CR3: 00000001d1ea2000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000000 ffffea0002c08700 0000000000000000 ffffffff838a91a0
 0000000000000000 0000000000000000 ffff8800ae2000a0 ffffffff81491301
 0000000000000000 ffffea0002c08700 0000000000000000 ffffffff838a91a0
Call Trace:
 <UNK> Code: 46 e8 a4 03 ed ff 48 83 c4 08 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 90 03 ed ff 31 d2 48 c7 c6 a0 91 8a 83 48 89 df e8 6f fe ff ff <0f> 0b e8 b8 dd 06 00 e9 21 ff ff ff 89 4d d4 e8 ab dd 06 00 8b 
RIP  [<ffffffff81491301>] dump_page mm/debug.c:105 [inline]
RIP  [<ffffffff81491301>] page_mapcount include/linux/mm.h:460 [inline]
RIP  [<ffffffff81491301>] dump_page_badflags+0x191/0x250 mm/debug.c:85
 RSP <ffff8800ae200030>
---[ end trace 9e2f6a1bb2beaec3 ]---