==================================================================
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 ffff8800b6f0b8d8 by task syz-executor7/4499

CPU: 1 PID: 4499 Comm: syz-executor7 Not tainted 4.4.152-ge5c5f1f #25
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 fcff009a68c60aa9 ffff8800a534f548 ffffffff81e15fed
 ffffea0002dbc2c0 ffff8800b6f0b8d8 0000000000000000 ffff8800b6f0b8d8
 0000000000001200 ffff8800a534f580 ffffffff8151b489 ffff8800b6f0b8d8
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 3561:
 [<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
 [<ffffffff831fe339>] __ip_route_output_key include/net/route.h:124 [inline]
 [<ffffffff831fe339>] ip_route_output_flow+0x29/0xa0 net/ipv4/route.c:2431
 [<ffffffff832da7c0>] udp_sendmsg+0x1480/0x1c70 net/ipv4/udp.c:1040
 [<ffffffff8349fbcd>] udpv6_sendmsg+0x12cd/0x24c0 net/ipv6/udp.c:1173
 [<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
 [<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

Freed by task 14:
 [<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
 [<ffffffff82fa5165>] dst_destroy net/core/dst.c:252 [inline]
 [<ffffffff82fa5165>] dst_destroy_rcu+0x15/0x40 net/core/dst.c:295
 [<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 ffff8800b6f0b8c0
 which belongs to the cache ip_dst_cache of size 208
The buggy address is located 24 bytes inside of
 208-byte region [ffff8800b6f0b8c0, ffff8800b6f0b990)
The buggy address belongs to the page:
page:ffffea00074bff80 count:1 mapcount:0 mapping:          (null) index:0x0
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory accessgeneral protection fault: 0000 [#1] PREEMPT SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 27260 Comm: udevd Not tainted 4.4.152-ge5c5f1f #25
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801bd7d1800 task.stack: ffff8801b7a50000
RIP: 0010:[<ffffffff81ebe958>]  [<ffffffff81ebe958>] find_stack lib/stackdepot.c:174 [inline]
RIP: 0010:[<ffffffff81ebe958>]  [<ffffffff81ebe958>] depot_save_stack+0x168/0x600 lib/stackdepot.c:225
RSP: 0000:ffff8801b7a57898  EFLAGS: 00010093
RAX: ffff8801bd7d1800 RBX: 00000000e501f9f3 RCX: 0000000070a74bbb
RDX: 0000000000000000 RSI: ffffffff81ebe958 RDI: ffff8801b7a57900
RBP: ffff8801b7a578f0 R08: ffff8801b7a57900 R09: 0000000000000000
R10: 0000000000000000 R11: ffff8801bd7d1800 R12: 9fa0016c00000de9
R13: 000000000001f9f3 R14: 000000000000000f R15: 0000000000000078
FS:  00007f0ad0fe77a0(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff8800a2764630 CR3: 00000001d027d000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0228002081ebe9b9 ffff8801b7a57918 f279131e00000003 ffff8801b7a57900
 0000000000000000 f279131ecf7305c3 0000000002280020 ffff8801d98fc8c0
 ffff8801c233c6c0 0000000000000000 ffff8801c233c6bf ffff8801b7a57b20
Call Trace:
 [<ffffffff814fd839>] save_stack+0xa9/0xd0 mm/kasan/kasan.c:518
 [<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
 [<ffffffff81157c21>] __sigqueue_alloc+0x1e1/0x400 kernel/signal.c:380
 [<ffffffff8115a3b5>] __send_signal+0x1a5/0x11b0 kernel/signal.c:1029
 [<ffffffff8115b40a>] send_signal+0x4a/0xc0 kernel/signal.c:1096
 [<ffffffff8115d33a>] specific_send_sig_info kernel/signal.c:1141 [inline]
 [<ffffffff8115d33a>] force_sig_info+0x20a/0x310 kernel/signal.c:1189
 [<ffffffff810d7908>] force_sig_info_fault.constprop.23+0x158/0x1b0 arch/x86/mm/fault.c:187
 [<ffffffff810d9549>] __bad_area_nosemaphore+0x219/0x310 arch/x86/mm/fault.c:807
 [<ffffffff810d966a>] bad_area_nosemaphore+0x2a/0x40 arch/x86/mm/fault.c:822
 [<ffffffff810d9b89>] __do_page_fault+0x149/0xa10 arch/x86/mm/fault.c:1187
 [<ffffffff810da477>] do_page_fault+0x27/0x30 arch/x86/mm/fault.c:1308
 [<ffffffff838cd948>] page_fault+0x28/0x30 arch/x86/entry/entry_64.S:1037
Code: 00 00 00 e8 0b 5c 49 ff 49 63 c6 48 c1 e0 03 49 89 c7 eb 12 e8 fa 5b 49 ff 4d 8b 24 24 4d 85 e4 0f 84 8a 00 00 00 e8 e8 5b 49 ff <41> 39 5c 24 08 75 e2 e8 dc 5b 49 ff 45 3b 74 24 0c 75 d6 e8 d0 
RIP  [<ffffffff81ebe958>] find_stack lib/stackdepot.c:174 [inline]
RIP  [<ffffffff81ebe958>] depot_save_stack+0x168/0x600 lib/stackdepot.c:225
 RSP <ffff8801b7a57898>
---[ end trace b9bc6f972dd4cc22 ]---