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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 ffff8801c2864018 by task syz-executor4/8062

CPU: 0 PID: 8062 Comm: syz-executor4 Not tainted 4.16.0-rc4+ #254
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
 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
 ___sys_sendmsg+0x767/0x8b0 net/socket.c:2047
 __sys_sendmsg+0xe5/0x210 net/socket.c:2081
 SYSC_sendmsg net/socket.c:2092 [inline]
 SyS_sendmsg+0x2d/0x50 net/socket.c:2088
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x453e69
RSP: 002b:00007f79c467dc68 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f79c467e6d4 RCX: 0000000000453e69
RDX: 0000000000000081 RSI: 000000002037ffc8 RDI: 0000000000000016
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000004c3 R14: 00000000006f72e8 R15: 0000000000000000

Allocated by task 7499:
 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
 __split_vma+0x10b/0x7b0 mm/mmap.c:2564
 split_vma+0x8f/0xc0 mm/mmap.c:2627
 mprotect_fixup+0x3f5/0x640 mm/mprotect.c:359
 do_mprotect_pkey+0x57d/0x900 mm/mprotect.c:497
 SYSC_mprotect mm/mprotect.c:522 [inline]
 SyS_mprotect+0x2a/0x40 mm/mprotect.c:519
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 7518:
 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
 remove_vma+0x162/0x1b0 mm/mmap.c:176
 exit_mmap+0x311/0x500 mm/mmap.c:3049
 __mmput kernel/fork.c:960 [inline]
 mmput+0x223/0x6d0 kernel/fork.c:981
 exit_mm kernel/exit.c:544 [inline]
 do_exit+0x90a/0x1ad0 kernel/exit.c:852
 do_group_exit+0x149/0x400 kernel/exit.c:968
 get_signal+0x73a/0x16d0 kernel/signal.c:2469
 do_signal+0x90/0x1e90 arch/x86/kernel/signal.c:809
 exit_to_usermode_loop+0x258/0x2f0 arch/x86/entry/common.c:162
 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
 do_syscall_64+0x6ec/0x940 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff8801c2864040
 which belongs to the cache vm_area_struct of size 200
The buggy address is located 40 bytes to the left of
 200-byte region [ffff8801c2864040, ffff8801c2864108)
The buggy address belongs to the page:
page:ffffea00070a1900 count:1 mapcount:0 mapping:ffff8801c2864040 index:0xffff8801c2864ca0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801c2864040 ffff8801c2864ca0 000000010000000c
raw: ffffea000706a3e0 ffffea00070ef8e0 ffff8801da5c3840 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c2863f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801c2863f80: 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801c2864000: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                            ^
 ffff8801c2864080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801c2864100: fb fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb
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