random: sshd: uninitialized urandom read (32 bytes read, 39 bits of entropy available)
random: sshd: uninitialized urandom read (32 bytes read, 40 bits of entropy available)
random: nonblocking pool is initialized
==================================================================
BUG: KASAN: use-after-free in l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830
Read of size 4 at addr ffff8801cf322280 by task syz-executor198/3827

CPU: 0 PID: 3827 Comm: syz-executor198 Not tainted 4.4.131-gfcce571 #36
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 bcba40d6a39e2df0 ffff8800af137cc0 ffffffff81e0df2d
 ffffea00073cc880 ffff8801cf322280 0000000000000000 ffff8801cf322280
 ffffffff82f18c50 ffff8800af137cf8 ffffffff8151520c ffff8801cf322280
Call Trace:
 [<ffffffff81e0df2d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e0df2d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff8151520c>] print_address_description+0x6c/0x216 mm/kasan/report.c:252
 [<ffffffff8151552b>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff8151552b>] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408
 [<ffffffff814f9004>] __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:428
 [<ffffffff83598724>] l2tp_session_queue_purge+0xf4/0x100 net/l2tp/l2tp_core.c:830
 [<ffffffff835a525f>] pppol2tp_release+0x1ff/0x310 net/l2tp/l2tp_ppp.c:509
 [<ffffffff82f18b26>] sock_release+0x96/0x1c0 net/socket.c:586
 [<ffffffff82f18c66>] sock_close+0x16/0x20 net/socket.c:1037
 [<ffffffff815225f5>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff81522b35>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118bb8f>] 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: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
 [<ffffffff838bfeb5>] int_ret_from_sys_call+0x25/0xa3

Allocated by task 3826:
 [<ffffffff810341d6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814f80d3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814f83b7>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814f83b7>] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814f4ad4>] __kmalloc+0x124/0x310 mm/slub.c:3613
 [<ffffffff8359db69>] kmalloc include/linux/slab.h:481 [inline]
 [<ffffffff8359db69>] kzalloc include/linux/slab.h:620 [inline]
 [<ffffffff8359db69>] l2tp_session_create+0x39/0x1030 net/l2tp/l2tp_core.c:1748
 [<ffffffff835a2870>] pppol2tp_connect+0x10f0/0x1910 net/l2tp/l2tp_ppp.c:725
 [<ffffffff82f1d548>] SYSC_connect+0x1b8/0x300 net/socket.c:1557
 [<ffffffff82f1fe84>] SyS_connect+0x24/0x30 net/socket.c:1538
 [<ffffffff838bfd25>] entry_SYSCALL_64_fastpath+0x22/0x9e

Freed by task 3826:
 [<ffffffff810341d6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814f80d3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814f8a02>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814f8a02>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814f5f04>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814f5f04>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814f5f04>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814f5f04>] kfree+0xf4/0x310 mm/slub.c:3749
 [<ffffffff8359aad0>] l2tp_session_free+0x170/0x200 net/l2tp/l2tp_core.c:1676
 [<ffffffff8359ce89>] l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:293 [inline]
 [<ffffffff8359ce89>] l2tp_tunnel_closeall+0x2b9/0x350 net/l2tp/l2tp_core.c:1279
 [<ffffffff8359d99b>] l2tp_udp_encap_destroy+0x8b/0xf0 net/l2tp/l2tp_core.c:1300
 [<ffffffff8348ff91>] udpv6_destroy_sock+0xb1/0xd0 net/ipv6/udp.c:1421
 [<ffffffff82f2e3fd>] sk_common_release+0x6d/0x300 net/core/sock.c:2680
 [<ffffffff8348ec45>] udp_lib_close+0x15/0x20 include/net/udp.h:190
 [<ffffffff832f68ff>] inet_release+0xff/0x1d0 net/ipv4/af_inet.c:435
 [<ffffffff83419490>] inet6_release+0x50/0x70 net/ipv6/af_inet6.c:424
 [<ffffffff82f18b26>] sock_release+0x96/0x1c0 net/socket.c:586
 [<ffffffff82f18c66>] sock_close+0x16/0x20 net/socket.c:1037
 [<ffffffff815225f5>] __fput+0x235/0x6f0 fs/file_table.c:208
 [<ffffffff81522b35>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118bb8f>] 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: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
 [<ffffffff838bfeb5>] int_ret_from_sys_call+0x25/0xa3

The buggy address belongs to the object at ffff8801cf322280
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 0 bytes inside of
 512-byte region [ffff8801cf322280, ffff8801cf322480)
The buggy address belongs to the page:
kasan: CONFIG_KASAN_INLINE enabled[   33.842117] page:ffffea00073cc880 count:1 mapcount:-2146697203 mapping:          (null) index:0x0
flags: 0xffff8801db319c40(active|reserved|private|private_2|swapcache|mappedtodisk|mlocked|uncached)
page dumped because: VM_BUG_ON_PAGE(PageSlab(page))
------------[ cut here ]------------
kernel BUG at include/linux/mm.h:464!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 3827 Comm: syz-executor198 Not tainted 4.4.131-gfcce571 #36
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d8d99800 task.stack: ffff8800af130000
RIP: 0010:[<ffffffff8148c947>]  [<ffffffff8148c947>] dump_page mm/debug.c:105 [inline]
RIP: 0010:[<ffffffff8148c947>]  [<ffffffff8148c947>] page_mapcount include/linux/mm.h:464 [inline]
RIP: 0010:[<ffffffff8148c947>]  [<ffffffff8148c947>] dump_page_badflags+0x57/0x70 mm/debug.c:85
RSP: 0018:ffff8800ac200030  EFLAGS: 00010093
RAX: 0000000000000000 RBX: ffffea00073cc880 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff81513249 RDI: ffff8801d8d9a0dc
RBP: ffff8800ac200060 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: ffffffff858f74cf R12: 0000000000000000
R13: ffffffff83aa9be0 R14: ffff8801cf322280 R15: ffff8801cf322480
FS:  00007efe25c71700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000205fafd2 CR3: 00000001d3e03000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000000 ffffea00073cc880 0000000000000000 ffffffff83aa9be0
 ffff8801cf322280 ffff8801cf322480 ffff8800ac2000a0 ffffffff8148c947
 0000000000000000 ffffea00073cc880 0000000000000000 ffffffff83aa9be0
Call Trace:
 <UNK> Code: 48 c1 ea 03 80 3c 02 00 75 23 48 8b 03 a8 80 0f 84 e6 67 08 00 e8 aa 48 ec ff 31 d2 48 c7 c6 e0 9b aa 83 48 89 df e8 a9 ff ff ff <0f> 0b 48 89 df e8 bf c6 06 00 eb d3 0f 1f 00 66 2e 0f 1f 84 00 
RIP  [<ffffffff8148c947>] dump_page mm/debug.c:105 [inline]
RIP  [<ffffffff8148c947>] page_mapcount include/linux/mm.h:464 [inline]
RIP  [<ffffffff8148c947>] dump_page_badflags+0x57/0x70 mm/debug.c:85
 RSP <ffff8800ac200030>
---[ end trace 471c7baf3b398427 ]---