==================================================================
BUG: KASAN: use-after-free in ip6_dst_idev include/net/ip6_fib.h:141 [inline]
BUG: KASAN: use-after-free in ip6_xmit+0x177c/0x1a00 net/ipv6/ip6_output.c:237
Read of size 8 at addr ffff8801cc992518 by task syz-executor4/10130

CPU: 0 PID: 10130 Comm: syz-executor4 Not tainted 4.4.152-ge5c5f1f #25
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 e9f219d3133f3c3b ffff8800b0e0f548 ffffffff81e15fed
 ffffea0007326480 ffff8801cc992518 0000000000000000 ffff8801cc992518
 0000000000001200 ffff8800b0e0f580 ffffffff8151b489 ffff8801cc992518
Call Trace:
 [<ffffffff81e15fed>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e15fed>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff8151b489>] print_address_description+0x6c/0x216 mm/kasan/report.c:252
 [<ffffffff8151b7a8>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff8151b7a8>] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408
 [<ffffffff814fe734>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
 [<ffffffff83435efc>] ip6_dst_idev include/net/ip6_fib.h:141 [inline]
 [<ffffffff83435efc>] ip6_xmit+0x177c/0x1a00 net/ipv6/ip6_output.c:237
 [<ffffffff834f60c5>] inet6_csk_xmit+0x245/0x490 net/ipv6/inet6_connection_sock.c:176
 [<ffffffff835a570c>] l2tp_xmit_core net/l2tp/l2tp_core.c:1084 [inline]
 [<ffffffff835a570c>] l2tp_xmit_skb+0xb9c/0xe80 net/l2tp/l2tp_core.c:1179
 [<ffffffff835b1c60>] pppol2tp_sendmsg+0x4e0/0x7d0 net/l2tp/l2tp_ppp.c:355
 [<ffffffff82f2727c>] sock_sendmsg_nosec net/socket.c:638 [inline]
 [<ffffffff82f2727c>] sock_sendmsg+0xcc/0x110 net/socket.c:648
 [<ffffffff82f28a41>] ___sys_sendmsg+0x441/0x880 net/socket.c:1975
 [<ffffffff82f2b0d4>] __sys_sendmmsg+0x1d4/0x2e0 net/socket.c:2053
 [<ffffffff83014b22>] C_SYSC_sendmmsg net/compat.c:728 [inline]
 [<ffffffff83014b22>] compat_SyS_sendmmsg+0x32/0x40 net/compat.c:725
 [<ffffffff81006d94>] do_syscall_32_irqs_on arch/x86/entry/common.c:393 [inline]
 [<ffffffff81006d94>] do_fast_syscall_32+0x324/0x8b0 arch/x86/entry/common.c:460
 [<ffffffff838cdec3>] sysenter_flags_fixed+0xd/0x1a

Allocated by task 7985:
 [<ffffffff81034676>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fd7d3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fdab7>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fdab7>] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814fe082>] kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:554
 [<ffffffff814f9b9e>] slab_post_alloc_hook mm/slub.c:1349 [inline]
 [<ffffffff814f9b9e>] slab_alloc_node mm/slub.c:2615 [inline]
 [<ffffffff814f9b9e>] slab_alloc mm/slub.c:2623 [inline]
 [<ffffffff814f9b9e>] kmem_cache_alloc+0xbe/0x2a0 mm/slub.c:2628
 [<ffffffff82fa5835>] dst_alloc+0xb5/0x1a0 net/core/dst.c:210
 [<ffffffff831f29c8>] rt_dst_alloc+0x78/0x430 net/ipv4/route.c:1478
 [<ffffffff831fbe8c>] __mkroute_output net/ipv4/route.c:2132 [inline]
 [<ffffffff831fbe8c>] __ip_route_output_key_hash+0x9ac/0x2380 net/ipv4/route.c:2344
 [<ffffffff832a50cd>] __ip_route_output_key include/net/route.h:124 [inline]
 [<ffffffff832a50cd>] ip_route_connect include/net/route.h:297 [inline]
 [<ffffffff832a50cd>] tcp_v4_connect+0xfdd/0x1890 net/ipv4/tcp_ipv4.c:171
 [<ffffffff833033e9>] __inet_stream_connect+0x2a9/0xc30 net/ipv4/af_inet.c:615
 [<ffffffff83252d60>] tcp_sendmsg_fastopen net/ipv4/tcp.c:1092 [inline]
 [<ffffffff83252d60>] tcp_sendmsg+0x1600/0x2b10 net/ipv4/tcp.c:1112
 [<ffffffff8330a633>] inet_sendmsg+0x203/0x4d0 net/ipv4/af_inet.c:755
 [<ffffffff82f2727c>] sock_sendmsg_nosec net/socket.c:638 [inline]
 [<ffffffff82f2727c>] sock_sendmsg+0xcc/0x110 net/socket.c:648
 [<ffffffff82f27f5c>] SYSC_sendto+0x21c/0x370 net/socket.c:1678
 [<ffffffff82f2a5f0>] SyS_sendto+0x40/0x50 net/socket.c:1646
 [<ffffffff81006d94>] do_syscall_32_irqs_on arch/x86/entry/common.c:393 [inline]
 [<ffffffff81006d94>] do_fast_syscall_32+0x324/0x8b0 arch/x86/entry/common.c:460
 [<ffffffff838cdec3>] sysenter_flags_fixed+0xd/0x1a

Freed by task 3850:
 [<ffffffff81034676>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fd7d3>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fe102>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fe102>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814fb2ee>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814fb2ee>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814fb2ee>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814fb2ee>] kmem_cache_free+0xbe/0x340 mm/slub.c:2881
 [<ffffffff82fa4ae5>] dst_destroy.part.6+0x1f5/0x330 net/core/dst.c:270
 [<ffffffff82fa4c35>] dst_destroy+0x15/0x20 net/core/dst.c:252
 [<ffffffff831f5a7c>] dst_free include/net/dst.h:425 [inline]
 [<ffffffff831f5a7c>] dst_rcu_free+0x9c/0xc0 include/net/dst.h:435
 [<ffffffff81288d47>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 [<ffffffff81288d47>] rcu_do_batch kernel/rcu/tree.c:2705 [inline]
 [<ffffffff81288d47>] invoke_rcu_callbacks kernel/rcu/tree.c:2973 [inline]
 [<ffffffff81288d47>] __rcu_process_callbacks kernel/rcu/tree.c:2940 [inline]
 [<ffffffff81288d47>] rcu_process_callbacks+0x927/0x1440 kernel/rcu/tree.c:2957
 [<ffffffff838cfa7c>] __do_softirq+0x22c/0xa1a kernel/softirq.c:273

The buggy address belongs to the object at ffff8801cc992500
 which belongs to the cache ip_dst_cache of size 208
The buggy address is located 24 bytes inside of
 208-byte region [ffff8801cc992500, ffff8801cc9925d0)
The buggy address belongs to the page:
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory accesskasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
------------[ cut here ]------------
WARNING: CPU: 1 PID: 3851 at kernel/sched/core.c:7946 __might_sleep+0x138/0x1a0 kernel/sched/core.c:7941()
do not call blocking ops when !TASK_RUNNING; state=1 set at [<ffffffff8113d81e>] do_wait+0x26e/0xa30 kernel/exit.c:1503