==================================================================
BUG: KASAN: use-after-free in ip6_dst_idev include/net/ip6_fib.h:141 [inline]
BUG: KASAN: use-after-free in ip6_xmit+0x193a/0x1ad0 net/ipv6/ip6_output.c:237
Read of size 8 at addr ffff8801d591a518 by task syzkaller506832/3315

CPU: 0 PID: 3315 Comm: syzkaller506832 Not tainted 4.4.113-g202e079 #1
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 df02a3aeec6b30fc ffff8801d0ddf5b8 ffffffff81d0278d
 ffffea0007564680 ffff8801d591a518 0000000000000000 ffff8801d591a518
 0000000000000040 ffff8801d0ddf5f0 ffffffff814fd053 ffff8801d591a518
Call Trace:
 [<ffffffff81d0278d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d0278d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff814fd053>] print_address_description+0x73/0x260 mm/kasan/report.c:252
 [<ffffffff814fd565>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff814fd565>] kasan_report+0x285/0x370 mm/kasan/report.c:408
 [<ffffffff814fd6c4>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
 [<ffffffff8330369a>] ip6_dst_idev include/net/ip6_fib.h:141 [inline]
 [<ffffffff8330369a>] ip6_xmit+0x193a/0x1ad0 net/ipv6/ip6_output.c:237
 [<ffffffff833c44d6>] inet6_csk_xmit+0x246/0x480 net/ipv6/inet6_connection_sock.c:176
 [<ffffffff83456b8f>] l2tp_xmit_core net/l2tp/l2tp_core.c:1084 [inline]
 [<ffffffff83456b8f>] l2tp_xmit_skb+0xc2f/0xea0 net/l2tp/l2tp_core.c:1179
 [<ffffffff83463674>] pppol2tp_sendmsg+0x584/0x7f0 net/l2tp/l2tp_ppp.c:355
 [<ffffffff82dea0aa>] sock_sendmsg_nosec net/socket.c:625 [inline]
 [<ffffffff82dea0aa>] sock_sendmsg+0xca/0x110 net/socket.c:635
 [<ffffffff82deb8d2>] ___sys_sendmsg+0x312/0x7c0 net/socket.c:1962
 [<ffffffff82dedefc>] __sys_sendmmsg+0x11c/0x2e0 net/socket.c:2047
 [<ffffffff82dee0f5>] SYSC_sendmmsg net/socket.c:2077 [inline]
 [<ffffffff82dee0f5>] SyS_sendmmsg+0x35/0x60 net/socket.c:2072
 [<ffffffff83771b5f>] entry_SYSCALL_64_fastpath+0x1c/0x98

Allocated by task 3299:
 [<ffffffff81035df6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fc0c3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fc38d>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fc38d>] kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814fc962>] kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:554
 [<ffffffff814f803a>] slab_post_alloc_hook mm/slub.c:1349 [inline]
 [<ffffffff814f803a>] slab_alloc_node mm/slub.c:2615 [inline]
 [<ffffffff814f803a>] slab_alloc mm/slub.c:2623 [inline]
 [<ffffffff814f803a>] kmem_cache_alloc+0xba/0x290 mm/slub.c:2628
 [<ffffffff82e679cf>] dst_alloc+0x11f/0x1a0 net/core/dst.c:210
 [<ffffffff830bfd78>] rt_dst_alloc+0x78/0x430 net/ipv4/route.c:1467
 [<ffffffff830c915e>] __mkroute_output net/ipv4/route.c:2120 [inline]
 [<ffffffff830c915e>] __ip_route_output_key_hash+0xa4e/0x2390 net/ipv4/route.c:2332
 [<ffffffff83193395>] __ip_route_output_key include/net/route.h:123 [inline]
 [<ffffffff83193395>] ip_route_connect include/net/route.h:296 [inline]
 [<ffffffff83193395>] __ip4_datagram_connect+0xa15/0x1150 net/ipv4/datagram.c:51
 [<ffffffff833b54e9>] __ip6_datagram_connect+0x4d9/0x1950 net/ipv6/datagram.c:59
 [<ffffffff833b698f>] ip6_datagram_connect+0x2f/0x50 net/ipv6/datagram.c:223
 [<ffffffff831cdd6b>] inet_dgram_connect+0x16b/0x1f0 net/ipv4/af_inet.c:550
 [<ffffffff82deabd6>] SYSC_connect+0x1b6/0x310 net/socket.c:1557
 [<ffffffff82ded444>] SyS_connect+0x24/0x30 net/socket.c:1538
 [<ffffffff83771b5f>] entry_SYSCALL_64_fastpath+0x1c/0x98

Freed by task 0:
 [<ffffffff81035df6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fc0c3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fc9e2>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fc9e2>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814f9127>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814f9127>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814f9127>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814f9127>] kmem_cache_free+0xc7/0x320 mm/slub.c:2881
 [<ffffffff82e6866e>] dst_destroy+0x20e/0x330 net/core/dst.c:270
 [<ffffffff82e68cb5>] dst_destroy_rcu+0x15/0x40 net/core/dst.c:295
 [<ffffffff81294084>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 [<ffffffff81294084>] rcu_do_batch kernel/rcu/tree.c:2705 [inline]
 [<ffffffff81294084>] invoke_rcu_callbacks kernel/rcu/tree.c:2973 [inline]
 [<ffffffff81294084>] __rcu_process_callbacks kernel/rcu/tree.c:2940 [inline]
 [<ffffffff81294084>] rcu_process_callbacks+0x7f4/0x14a0 kernel/rcu/tree.c:2957
 [<ffffffff83775057>] __do_softirq+0x227/0xa38 kernel/softirq.c:273

The buggy address belongs to the object at ffff8801d591a500
 which belongs to the cache ip_dst_cache of size 208
The buggy address is located 24 bytes inside of
 208-byte region [ffff8801d591a500, ffff8801d591a5d0)
The buggy address belongs to the page:
PANIC: double fault, error_code: 0x0
CPU: 0 PID: 3315 Comm: syzkaller506832 Not tainted 4.4.113-g202e079 #1
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d2155f00 task.stack: ffff8801d0dd8000
RIP: 0010:[<ffffffff8148f75d>]  [<ffffffff8148f75d>] dump_page_badflags+0xd/0x250 mm/debug.c:84
RSP: 0018:ffff880100000000  EFLAGS: 00010046
RAX: ffff8801d2155f00 RBX: ffffea0007564680 RCX: ffffffff8148f8d0
RDX: 0000000000000000 RSI: ffffffff838a8de0 RDI: ffffea0007564680
RBP: ffff880100000018 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000002 R11: fffffbfff0ad7e26 R12: 0000000000000000
R13: ffffffff838a8de0 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000002125880(0063) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff8800fffffff8 CR3: 00000001d31bc000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:

Call Trace:
 <UNK> 
Code: ff e8 78 df 06 00 e9 50 fd ff ff e8 6e df 06 00 e9 1d fd ff ff 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 41 57 41 56 41 55 49 89 f5 <41> 54 49 89 d4 53 48 89 fb 48 83 ec 08 e8 b1 04 ed ff 48 8d 7b