==================================================================
BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:185 [inline]
BUG: KASAN: use-after-free in sk_dst_get include/net/sock.h:1772 [inline]
BUG: KASAN: use-after-free in pppol2tp_session_init+0x4b4/0x4d0 net/l2tp/l2tp_ppp.c:616
Read of size 8 at addr ffff8880a7d319e8 by task syz-executor.4/12147

CPU: 0 PID: 12147 Comm: syz-executor.4 Not tainted 4.14.267-syzkaller #0
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+0x1b2/0x281 lib/dump_stack.c:58
 print_address_description.cold+0x54/0x1d3 mm/kasan/report.c:252
 kasan_report_error.cold+0x8a/0x191 mm/kasan/report.c:351
 kasan_report mm/kasan/report.c:409 [inline]
 __asan_report_load8_noabort+0x68/0x70 mm/kasan/report.c:430
 __read_once_size include/linux/compiler.h:185 [inline]
 sk_dst_get include/net/sock.h:1772 [inline]
 pppol2tp_session_init+0x4b4/0x4d0 net/l2tp/l2tp_ppp.c:616
 pppol2tp_connect+0xd11/0x1370 net/l2tp/l2tp_ppp.c:790
 SYSC_connect net/socket.c:1655 [inline]
 SyS_connect+0x1f4/0x240 net/socket.c:1636
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x7fa80178c059
RSP: 002b:00007fa800101168 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007fa80189ef60 RCX: 00007fa80178c059
RDX: 000000000000002e RSI: 0000000020000000 RDI: 0000000000000004
RBP: 00007fa8017e608d R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fff82828c2f R14: 00007fa800101300 R15: 0000000000022000

Allocated by task 12139:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:551
 kmem_cache_alloc+0x124/0x3c0 mm/slab.c:3552
 sk_prot_alloc+0x5f/0x290 net/core/sock.c:1478
 sk_alloc+0x36/0xcd0 net/core/sock.c:1538
 inet6_create net/ipv6/af_inet6.c:183 [inline]
 inet6_create+0x2df/0xe20 net/ipv6/af_inet6.c:110
 __sock_create+0x303/0x620 net/socket.c:1275
 sock_create net/socket.c:1315 [inline]
 SYSC_socket net/socket.c:1345 [inline]
 SyS_socket+0xd1/0x1b0 net/socket.c:1325
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb

Freed by task 12147:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0xc3/0x1a0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kmem_cache_free+0x7c/0x2b0 mm/slab.c:3758
 sk_prot_free net/core/sock.c:1519 [inline]
 __sk_destruct+0x442/0x760 net/core/sock.c:1600
 __rcu_reclaim kernel/rcu/rcu.h:195 [inline]
 rcu_do_batch kernel/rcu/tree.c:2699 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2962 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2929 [inline]
 rcu_process_callbacks+0x780/0x1180 kernel/rcu/tree.c:2946
 __do_softirq+0x24d/0x9ff kernel/softirq.c:288

The buggy address belongs to the object at ffff8880a7d317c0
 which belongs to the cache UDPv6 of size 1728
The buggy address is located 552 bytes inside of
 1728-byte region [ffff8880a7d317c0, ffff8880a7d31e80)
The buggy address belongs to the page:
page:ffffea00029f4c40 count:1 mapcount:0 mapping:ffff8880a7d31080 index:0x0
flags: 0xfff00000000100(slab)
raw: 00fff00000000100 ffff8880a7d31080 0000000000000000 0000000100000002
raw: ffffea00026c9fa0 ffffea0002a51fe0 ffff8880a502ec80 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a7d31880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a7d31900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880a7d31980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                          ^
 ffff8880a7d31a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a7d31a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================