l2tp_core: tunl 2: sockfd_lookup(fd=11) returned -9
l2tp_core: tunl 2: sockfd_lookup(fd=11) returned -9
l2tp_core: tunl 2: sockfd_lookup(fd=11) returned -9
l2tp_core: tunl 2: sockfd_lookup(fd=11) returned -9
==================================================================
BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:188 [inline]
BUG: KASAN: use-after-free in sk_dst_get include/net/sock.h:1767 [inline]
BUG: KASAN: use-after-free in pppol2tp_session_init net/l2tp/l2tp_ppp.c:587 [inline]
BUG: KASAN: use-after-free in pppol2tp_connect+0x1ab3/0x1de0 net/l2tp/l2tp_ppp.c:747
Read of size 8 at addr ffff8801be0f1568 by task syz-executor4/5376

CPU: 0 PID: 5376 Comm: syz-executor4 Not tainted 4.16.0+ #288
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1a7/0x27d lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report+0x23c/0x360 mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 __read_once_size include/linux/compiler.h:188 [inline]
 sk_dst_get include/net/sock.h:1767 [inline]
 pppol2tp_session_init net/l2tp/l2tp_ppp.c:587 [inline]
 pppol2tp_connect+0x1ab3/0x1de0 net/l2tp/l2tp_ppp.c:747
 __sys_connect+0x213/0x4a0 net/socket.c:1664
 SYSC_connect net/socket.c:1675 [inline]
 SyS_connect+0x24/0x30 net/socket.c:1672
 do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
 do_fast_syscall_32+0x3ec/0xf9f arch/x86/entry/common.c:392
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7f4bc99
RSP: 002b:00000000f7f470ac EFLAGS: 00000282 ORIG_RAX: 000000000000016a
RAX: ffffffffffffffda RBX: 000000000000000b RCX: 0000000020e92000
RDX: 000000000000002e RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 5386:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:552
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3542
 sk_prot_alloc+0x65/0x2a0 net/core/sock.c:1465
 sk_alloc+0x105/0x1450 net/core/sock.c:1525
 inet_create+0x47c/0xf50 net/ipv4/af_inet.c:320
 __sock_create+0x4d4/0x850 net/socket.c:1285
 sock_create net/socket.c:1325 [inline]
 __sys_socket+0xea/0x210 net/socket.c:1355
 SYSC_socket net/socket.c:1364 [inline]
 SyS_socket+0x24/0x30 net/socket.c:1362
 do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
 do_fast_syscall_32+0x3ec/0xf9f arch/x86/entry/common.c:392
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139

Freed by task 5211:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
 __cache_free mm/slab.c:3486 [inline]
 kmem_cache_free+0x83/0x2a0 mm/slab.c:3744
 sk_prot_free net/core/sock.c:1506 [inline]
 __sk_destruct+0x690/0x9f0 net/core/sock.c:1590
 sk_destruct+0x47/0x80 net/core/sock.c:1598
 __sk_free+0xf1/0x2b0 net/core/sock.c:1609
 sk_free+0x2a/0x40 net/core/sock.c:1620
 sock_put include/net/sock.h:1659 [inline]
 l2tp_tunnel_free net/l2tp/l2tp_core.c:160 [inline]
 l2tp_tunnel_dec_refcount net/l2tp/l2tp_core.h:264 [inline]
 l2tp_tunnel_del_work+0x474/0x6a0 net/l2tp/l2tp_core.c:1307
 process_one_work+0xc97/0x1c40 kernel/workqueue.c:2113
 worker_thread+0x1c3/0x1380 kernel/workqueue.c:2247
 kthread+0x33c/0x400 kernel/kthread.c:238
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:411

The buggy address belongs to the object at ffff8801be0f1340
 which belongs to the cache UDP of size 1472
The buggy address is located 552 bytes inside of
 1472-byte region [ffff8801be0f1340, ffff8801be0f1900)
The buggy address belongs to the page:
page:ffffea0006f83c00 count:1 mapcount:0 mapping:ffff8801be0f0080 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801be0f0080 0000000000000000 0000000100000005
raw: ffffea0007268a20 ffffea0006c00820 ffff8801d815c4c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801be0f1400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801be0f1480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801be0f1500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                          ^
 ffff8801be0f1580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801be0f1600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================