==================================================================
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 ffff8801cfb7da18 by task syz-executor0/20097

CPU: 1 PID: 20097 Comm: syz-executor0 Not tainted 4.4.153-g5e24b4e #90
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 4b15be7bba499d18 ffff8800b2e0f5c8 ffffffff81e162ed
 ffffea00073edf40 ffff8801cfb7da18 0000000000000000 ffff8801cfb7da18
 0000000000001000 ffff8800b2e0f600 ffffffff8151b4d9 ffff8801cfb7da18
Call Trace:
 [<ffffffff81e162ed>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e162ed>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff8151b4d9>] print_address_description+0x6c/0x216 mm/kasan/report.c:252
 [<ffffffff8151b7f8>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff8151b7f8>] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408
 [<ffffffff814fe784>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
 [<ffffffff834361fc>] ip6_dst_idev include/net/ip6_fib.h:141 [inline]
 [<ffffffff834361fc>] ip6_xmit+0x177c/0x1a00 net/ipv6/ip6_output.c:237
 [<ffffffff834f63c5>] inet6_csk_xmit+0x245/0x490 net/ipv6/inet6_connection_sock.c:176
 [<ffffffff835a5a0c>] l2tp_xmit_core net/l2tp/l2tp_core.c:1084 [inline]
 [<ffffffff835a5a0c>] l2tp_xmit_skb+0xb9c/0xe80 net/l2tp/l2tp_core.c:1179
 [<ffffffff835b1f60>] pppol2tp_sendmsg+0x4e0/0x7d0 net/l2tp/l2tp_ppp.c:355
 [<ffffffff82f2757c>] sock_sendmsg_nosec net/socket.c:638 [inline]
 [<ffffffff82f2757c>] sock_sendmsg+0xcc/0x110 net/socket.c:648
 [<ffffffff82f28d41>] ___sys_sendmsg+0x441/0x880 net/socket.c:1975
 [<ffffffff82f2b32e>] __sys_sendmmsg+0x12e/0x2e0 net/socket.c:2060
 [<ffffffff82f2b515>] SYSC_sendmmsg net/socket.c:2090 [inline]
 [<ffffffff82f2b515>] SyS_sendmmsg+0x35/0x60 net/socket.c:2085
 [<ffffffff838cc865>] entry_SYSCALL_64_fastpath+0x22/0x9e

Allocated by task 19354:
 [<ffffffff81034676>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fd823>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fdb07>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fdb07>] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:616
 [<ffffffff814fe0d2>] kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:554
 [<ffffffff814f9bee>] slab_post_alloc_hook mm/slub.c:1349 [inline]
 [<ffffffff814f9bee>] slab_alloc_node mm/slub.c:2615 [inline]
 [<ffffffff814f9bee>] slab_alloc mm/slub.c:2623 [inline]
 [<ffffffff814f9bee>] kmem_cache_alloc+0xbe/0x2a0 mm/slub.c:2628
 [<ffffffff82fa5b35>] dst_alloc+0xb5/0x1a0 net/core/dst.c:210
 [<ffffffff831f2cc8>] rt_dst_alloc+0x78/0x430 net/ipv4/route.c:1478
 [<ffffffff831fc18c>] __mkroute_output net/ipv4/route.c:2132 [inline]
 [<ffffffff831fc18c>] __ip_route_output_key_hash+0x9ac/0x2380 net/ipv4/route.c:2344
 [<ffffffff831fe639>] __ip_route_output_key include/net/route.h:124 [inline]
 [<ffffffff831fe639>] ip_route_output_flow+0x29/0xa0 net/ipv4/route.c:2431
 [<ffffffff832daac0>] udp_sendmsg+0x1480/0x1c70 net/ipv4/udp.c:1040
 [<ffffffff8349fecd>] udpv6_sendmsg+0x12cd/0x24c0 net/ipv6/udp.c:1173
 [<ffffffff8330a933>] inet_sendmsg+0x203/0x4d0 net/ipv4/af_inet.c:755
 [<ffffffff82f2757c>] sock_sendmsg_nosec net/socket.c:638 [inline]
 [<ffffffff82f2757c>] sock_sendmsg+0xcc/0x110 net/socket.c:648
 [<ffffffff82f28d41>] ___sys_sendmsg+0x441/0x880 net/socket.c:1975
 [<ffffffff82f2b32e>] __sys_sendmmsg+0x12e/0x2e0 net/socket.c:2060
 [<ffffffff82f2b515>] SYSC_sendmmsg net/socket.c:2090 [inline]
 [<ffffffff82f2b515>] SyS_sendmmsg+0x35/0x60 net/socket.c:2085
 [<ffffffff838cc865>] entry_SYSCALL_64_fastpath+0x22/0x9e

Freed by task 3:
 [<ffffffff81034676>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff814fd823>] save_stack+0x43/0xd0 mm/kasan/kasan.c:512
 [<ffffffff814fe152>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff814fe152>] kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:589
 [<ffffffff814fb33e>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff814fb33e>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff814fb33e>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff814fb33e>] kmem_cache_free+0xbe/0x340 mm/slub.c:2881
 [<ffffffff82fa4de5>] dst_destroy.part.6+0x1f5/0x330 net/core/dst.c:270
 [<ffffffff82fa5465>] dst_destroy net/core/dst.c:252 [inline]
 [<ffffffff82fa5465>] dst_destroy_rcu+0x15/0x40 net/core/dst.c:295
 [<ffffffff81288d97>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 [<ffffffff81288d97>] rcu_do_batch kernel/rcu/tree.c:2705 [inline]
 [<ffffffff81288d97>] invoke_rcu_callbacks kernel/rcu/tree.c:2973 [inline]
 [<ffffffff81288d97>] __rcu_process_callbacks kernel/rcu/tree.c:2940 [inline]
 [<ffffffff81288d97>] rcu_process_callbacks+0x927/0x1440 kernel/rcu/tree.c:2957
 [<ffffffff838cfd7c>] __do_softirq+0x22c/0xa1a kernel/softirq.c:273

The buggy address belongs to the object at ffff8801cfb7da00
 which belongs to the cache ip_dst_cache of size 208
The buggy address is located 24 bytes inside of
 208-byte region [ffff8801cfb7da00, ffff8801cfb7dad0)
The buggy address belongs to the page:
------------[ cut here ]------------
WARNING: CPU: 0 PID: 3752 at kernel/locking/lockdep.c:3190 __lock_acquire+0x265f/0x5270 kernel/locking/lockdep.c:3190()
DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS)