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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+0x1ce9/0x2090 net/ipv6/ip6_output.c:264
Read of size 8 at addr ffff8801d53c4018 by task syz-executor1/1988

CPU: 0 PID: 1988 Comm: syz-executor1 Not tainted 4.15.0-rc9+ #206
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+0x194/0x257 lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 ip6_dst_idev include/net/ip6_fib.h:192 [inline]
 ip6_xmit+0x1ce9/0x2090 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:1096 [inline]
 l2tp_xmit_skb+0x105f/0x1410 net/l2tp/l2tp_core.c:1191
 pppol2tp_sendmsg+0x470/0x670 net/l2tp/l2tp_ppp.c:341
 sock_sendmsg_nosec net/socket.c:630 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:640
 ___sys_sendmsg+0x767/0x8b0 net/socket.c:2020
 __sys_sendmsg+0xe5/0x210 net/socket.c:2054
 SYSC_sendmsg net/socket.c:2065 [inline]
 SyS_sendmsg+0x2d/0x50 net/socket.c:2061
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x452f19
RSP: 002b:00007fe914928c58 EFLAGS: 00000212 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452f19
RDX: 0000000000000081 RSI: 000000002037ffc8 RDI: 0000000000000014
RBP: 000000000000005c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006ef940
R13: 00000000ffffffff R14: 00007fe9149296d4 R15: 0000000000000000

Allocated by task 32692:
 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:551
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3544
 getname_flags+0xcb/0x580 fs/namei.c:138
 user_path_at_empty+0x2d/0x50 fs/namei.c:2590
 user_path_at include/linux/namei.h:57 [inline]
 SYSC_chdir fs/open.c:440 [inline]
 SyS_chdir+0xb0/0x200 fs/open.c:434
 entry_SYSCALL_64_fastpath+0x29/0xa0

Freed by task 32692:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3488 [inline]
 kmem_cache_free+0x83/0x2a0 mm/slab.c:3746
 putname+0xee/0x130 fs/namei.c:258
 filename_lookup+0x315/0x500 fs/namei.c:2345
 user_path_at_empty+0x40/0x50 fs/namei.c:2590
 user_path_at include/linux/namei.h:57 [inline]
 SYSC_chdir fs/open.c:440 [inline]
 SyS_chdir+0xb0/0x200 fs/open.c:434
 entry_SYSCALL_64_fastpath+0x29/0xa0

The buggy address belongs to the object at ffff8801d53c4500
 which belongs to the cache names_cache of size 4096
The buggy address is located 1256 bytes to the left of
 4096-byte region [ffff8801d53c4500, ffff8801d53c5500)
The buggy address belongs to the page:
page:ffffea000754f100 count:1 mapcount:0 mapping:ffff8801d53c4500 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801d53c4500 0000000000000000 0000000100000001
raw: ffffea00075436a0 ffffea00075776a0 ffff8801dae2c600 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d53c3f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801d53c3f80: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
>ffff8801d53c4000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                            ^
 ffff8801d53c4080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801d53c4100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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