audit: type=1400 audit(1582840088.908:33161): avc:  denied  { map } for  pid=4340 comm="modprobe" path="/lib/x86_64-linux-gnu/libc-2.13.so" dev="sda1" ino=2784 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:object_r:file_t:s0 tclass=file permissive=1
==================================================================
BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:183 [inline]
BUG: KASAN: use-after-free in sk_dst_get include/net/sock.h:1766 [inline]
BUG: KASAN: use-after-free in pppol2tp_connect+0x15b4/0x17b0 net/l2tp/l2tp_ppp.c:749
Read of size 8 at addr ffff88808baa22a8 by task syz-executor.4/4346

CPU: 1 PID: 4346 Comm: syz-executor.4 Not tainted 4.14.171-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+0x13e/0x194 lib/dump_stack.c:58
 print_address_description.cold+0x7c/0x1e2 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report mm/kasan/report.c:409 [inline]
 kasan_report.cold+0xa9/0x2ae mm/kasan/report.c:393
 __read_once_size include/linux/compiler.h:183 [inline]
 sk_dst_get include/net/sock.h:1766 [inline]
 pppol2tp_connect+0x15b4/0x17b0 net/l2tp/l2tp_ppp.c:749
 SYSC_connect+0x1c6/0x250 net/socket.c:1655
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45c479
RSP: 002b:00007f304c02dc78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007f304c02e6d4 RCX: 000000000045c479
RDX: 000000000000002e RSI: 0000000020000000 RDI: 0000000000000003
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000008d R14: 00000000004c2e4e R15: 000000000076bf2c

Allocated by task 4293:
 save_stack+0x32/0xa0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc mm/kasan/kasan.c:551 [inline]
 kasan_kmalloc+0xbf/0xe0 mm/kasan/kasan.c:529
 kmem_cache_alloc+0x127/0x770 mm/slab.c:3552
 sk_prot_alloc+0x5f/0x290 net/core/sock.c:1461
 sk_alloc+0x36/0xd60 net/core/sock.c:1521
 inet6_create net/ipv6/af_inet6.c:183 [inline]
 inet6_create+0x2df/0xe20 net/ipv6/af_inet6.c:110
 __sock_create+0x2f2/0x620 net/socket.c:1275
 sock_create net/socket.c:1315 [inline]
 SYSC_socket net/socket.c:1345 [inline]
 SyS_socket+0xd2/0x170 net/socket.c:1325
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 4291:
 save_stack+0x32/0xa0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x75/0xc0 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:1502 [inline]
 __sk_destruct+0x3b1/0x640 net/core/sock.c:1581
 sk_destruct+0x97/0xc0 net/core/sock.c:1596
 __sk_free+0x4c/0x220 net/core/sock.c:1604
 sk_free+0x2b/0x40 net/core/sock.c:1615
 sock_put include/net/sock.h:1658 [inline]
 sk_common_release+0x1ec/0x2f0 net/core/sock.c:3019
 inet_release+0xdf/0x1b0 net/ipv4/af_inet.c:425
 inet6_release+0x4c/0x70 net/ipv6/af_inet6.c:450
 __sock_release+0xcd/0x2b0 net/socket.c:602
 sock_close+0x15/0x20 net/socket.c:1139
 __fput+0x25f/0x790 fs/file_table.c:210
 task_work_run+0x113/0x190 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 exit_to_usermode_loop+0x1d6/0x220 arch/x86/entry/common.c:164
 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
 do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff88808baa2080
 which belongs to the cache UDPv6 of size 1728
The buggy address is located 552 bytes inside of
 1728-byte region [ffff88808baa2080, ffff88808baa2740)
The buggy address belongs to the page:
page:ffffea00022ea880 count:1 mapcount:0 mapping:ffff88808baa2080 index:0x0
flags: 0xfffe0000000100(slab)
raw: 00fffe0000000100 ffff88808baa2080 0000000000000000 0000000100000002
raw: ffffea00021c4020 ffffea00024b10e0 ffff88809bfba0c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808baa2180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808baa2200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88808baa2280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff88808baa2300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808baa2380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================