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BUG: KASAN: slab-out-of-bounds in ip6_dst_idev include/net/ip6_fib.h:192 [inline]
BUG: KASAN: slab-out-of-bounds in ip6_xmit+0x1f76/0x2260 net/ipv6/ip6_output.c:264
Read of size 8 at addr ffff8801c2def018 by task syz-executor6/28375

CPU: 0 PID: 28375 Comm: syz-executor6 Not tainted 4.16.0-rc4+ #260
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x24d lib/dump_stack.c:53
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=43880 sclass=netlink_route_socket pig=28359 comm=syz-executor1
 print_address_description+0x73/0x250 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report+0x23c/0x360 mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 ip6_dst_idev include/net/ip6_fib.h:192 [inline]
 ip6_xmit+0x1f76/0x2260 net/ipv6/ip6_output.c:264
 inet6_csk_xmit+0x2fc/0x580 net/ipv6/inet6_connection_sock.c:139
 l2tp_xmit_core net/l2tp/l2tp_core.c:1053 [inline]
 l2tp_xmit_skb+0x105f/0x1410 net/l2tp/l2tp_core.c:1148
 pppol2tp_sendmsg+0x470/0x670 net/l2tp/l2tp_ppp.c:341
 sock_sendmsg_nosec net/socket.c:629 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:639
 SYSC_sendto+0x361/0x5c0 net/socket.c:1748
 SyS_sendto+0x40/0x50 net/socket.c:1716
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
dst_release: dst:00000000586acfd2 refcnt:-1
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x453e69
RSP: 002b:00007f9c79bc0c68 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
dst_release: dst:0000000028e30aea refcnt:-1
RAX: ffffffffffffffda RBX: 00007f9c79bc16d4 RCX: 0000000000453e69
RDX: 000000000000100b RSI: 0000000020001180 RDI: 0000000000000015
RBP: 000000000072bea0 R08: 00000000200021c0 R09: 0000000000000080
R10: 0000000000040001 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000004ca R14: 00000000006f7390 R15: 0000000000000000

Allocated by task 5860:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:552
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3541
 dup_fd+0x110/0xdf0 fs/file.c:280
 copy_files kernel/fork.c:1337 [inline]
 copy_process.part.38+0x2053/0x4b60 kernel/fork.c:1781
 copy_process kernel/fork.c:1606 [inline]
 _do_fork+0x1f7/0xf70 kernel/fork.c:2087
 kernel_thread+0x34/0x40 kernel/fork.c:2146
 call_usermodehelper_exec_sync kernel/umh.c:123 [inline]
 call_usermodehelper_exec_work+0xfe/0x2c0 kernel/umh.c:175
 process_one_work+0xc47/0x1bb0 kernel/workqueue.c:2113
 worker_thread+0x223/0x1990 kernel/workqueue.c:2247
 kthread+0x33c/0x400 kernel/kthread.c:238
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406

Freed by task 26386:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
 __cache_free mm/slab.c:3485 [inline]
 kmem_cache_free+0x83/0x2a0 mm/slab.c:3743
 put_files_struct+0x2b0/0x320 fs/file.c:421
 exit_files+0x83/0xb0 fs/file.c:445
 do_exit+0x994/0x1ad0 kernel/exit.c:860
 do_group_exit+0x149/0x400 kernel/exit.c:968
 SYSC_exit_group kernel/exit.c:979 [inline]
 SyS_exit_group+0x1d/0x20 kernel/exit.c:977
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff8801c2def0c0
 which belongs to the cache files_cache of size 832
The buggy address is located 168 bytes to the left of
 832-byte region [ffff8801c2def0c0, ffff8801c2def400)
The buggy address belongs to the page:
page:ffffea00070b7bc0 count:1 mapcount:0 mapping:ffff8801c2def0c0 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801c2def0c0 0000000000000000 0000000100000004
raw: ffffea0006eb5fa0 ffffea0006f0c4a0 ffff8801da5c3cc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c2deef00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801c2deef80: 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801c2def000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                            ^
 ffff8801c2def080: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
 ffff8801c2def100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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