pktgen: kernel_thread() failed for cpu 1
pktgen: Cannot create thread for cpu 1 (-4)
==================================================================
BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:243 [inline]
BUG: KASAN: use-after-free in sk_dst_get include/net/sock.h:1695 [inline]
BUG: KASAN: use-after-free in pppol2tp_connect+0x1580/0x18f0 net/l2tp/l2tp_ppp.c:746
Read of size 8 at addr ffff8801b9920858 by task syz-executor4/9712

CPU: 0 PID: 9712 Comm: syz-executor4 Not tainted 4.9.118-g47b77b8 #20
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff88019901fad0 ffffffff81eb4b89 ffffea0006e64800 ffff8801b9920858
 0000000000000000 ffff8801b9920858 0000000000000000 ffff88019901fb08
 ffffffff81567f29 ffff8801b9920858 0000000000000008 0000000000000000
Call Trace:
 [<ffffffff81eb4b89>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb4b89>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81567f29>] print_address_description+0x6c/0x234 mm/kasan/report.c:256
 [<ffffffff81568333>] kasan_report_error mm/kasan/report.c:355 [inline]
 [<ffffffff81568333>] kasan_report.cold.6+0x242/0x2fe mm/kasan/report.c:412
 [<ffffffff8153beb4>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 [<ffffffff836c9280>] __read_once_size include/linux/compiler.h:243 [inline]
 [<ffffffff836c9280>] sk_dst_get include/net/sock.h:1695 [inline]
 [<ffffffff836c9280>] pppol2tp_connect+0x1580/0x18f0 net/l2tp/l2tp_ppp.c:746
IPVS: Creating netns size=2536 id=14
 [<ffffffff83019958>] SYSC_connect+0x1b8/0x300 net/socket.c:1563
 [<ffffffff8301c224>] SyS_connect+0x24/0x30 net/socket.c:1544
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fca93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Allocated by task 9041:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 save_stack+0x43/0xd0 mm/kasan/kasan.c:505
 set_track mm/kasan/kasan.c:517 [inline]
 kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:609
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:547
 slab_post_alloc_hook mm/slab.h:417 [inline]
 slab_alloc_node mm/slub.c:2715 [inline]
 slab_alloc mm/slub.c:2723 [inline]
 kmem_cache_alloc+0xbe/0x290 mm/slub.c:2728
 sk_prot_alloc+0x69/0x290 net/core/sock.c:1332
 sk_alloc+0x3a/0x3a0 net/core/sock.c:1394
 inet6_create+0x2d9/0xd80 net/ipv6/af_inet6.c:198
 __sock_create+0x2ef/0x5f0 net/socket.c:1183
 sock_create net/socket.c:1223 [inline]
 SYSC_socket net/socket.c:1253 [inline]
 SyS_socket+0xf0/0x1b0 net/socket.c:1233
 do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Freed by task 3876:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 save_stack+0x43/0xd0 mm/kasan/kasan.c:505
 set_track mm/kasan/kasan.c:517 [inline]
 kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:582
 slab_free_hook mm/slub.c:1355 [inline]
 slab_free_freelist_hook mm/slub.c:1377 [inline]
 slab_free mm/slub.c:2958 [inline]
 kmem_cache_free+0xbe/0x310 mm/slub.c:2980
 sk_prot_free net/core/sock.c:1375 [inline]
 __sk_destruct+0x3b9/0x590 net/core/sock.c:1455
 __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 rcu_process_callbacks+0x8ae/0x12b0 kernel/rcu/tree.c:3037
 __do_softirq+0x20b/0x937 kernel/softirq.c:284

The buggy address belongs to the object at ffff8801b9920680
 which belongs to the cache UDPv6 of size 1496
The buggy address is located 472 bytes inside of
 1496-byte region [ffff8801b9920680, ffff8801b9920c58)
The buggy address belongs to the page:
9pnet: Insufficient options for proto=fd
page:ffffea0006e64800 count:1 mapcount:0 mapping:          (null) index:0x0 compound_mapcount: 0
flags: 0x8000000000004080(slab|head)
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801b9920700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
BTRFS: device fsid ecf6f2a3-2997-48ae-b81e-1b00920efd9a devid 0 transid 0 /dev/loop5
 ffff8801b9920780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801b9920800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                    ^
 ffff8801b9920880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801b9920900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
9pnet: Insufficient options for proto=fd