KASAN: invalid-free in putname

[syzbot]

Hello,

syzbot hit the following crash on net-next commit
5d22d47b9ed96eddb35821dc2cc4f629f45827f7 (Tue Mar 27 17:33:21 2018 +0000)
Merge branch 'sfc-filter-locking'
syzbot dashboard link:
https://syzkaller.appspot.com/bug?extid=021e1d2ae5a6560008eb

So far this crash happened 2 times on net-next.
Unfortunately, I don't have any reproducer for this crash yet.
Raw console output:
https://syzkaller.appspot.com/x/log.txt?id=4558249521053696
Kernel config:
https://syzkaller.appspot.com/x/.config?id=4372867303600475372
compiler: gcc (GCC) 7.1.1 20170620
CC: [linux-...@vger.kernel.org linux-...@vger.kernel.org
vi...@zeniv.linux.org.uk]

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Reported-by: syzbot+021e1d...@syzkaller.appspotmail.com
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==================================================================
BUG: KASAN: double-free or invalid-free in putname+0xee/0x130 fs/namei.c:258

CPU: 1 PID: 13445 Comm: kworker/u4:15 Not tainted 4.16.0-rc6+ #284
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_invalid_free+0x55/0x80 mm/kasan/report.c:336
__kasan_slab_free+0x145/0x170 mm/kasan/kasan.c:500
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
putname+0xee/0x130 fs/namei.c:258
open_exec+0x41/0x60 fs/exec.c:882
load_elf_binary+0x1348/0x4c10 fs/binfmt_elf.c:775
search_binary_handler+0x142/0x6b0 fs/exec.c:1638
exec_binprm fs/exec.c:1680 [inline]
do_execveat_common.isra.30+0x1754/0x23c0 fs/exec.c:1802
do_execve+0x31/0x40 fs/exec.c:1847
call_usermodehelper_exec_async+0x457/0x8f0 kernel/umh.c:100
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406

Allocated by task 13422:
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
getname_flags+0xcb/0x580 fs/namei.c:138
getname fs/namei.c:209 [inline]
SYSC_symlinkat fs/namei.c:4121 [inline]
SyS_symlinkat fs/namei.c:4112 [inline]
SYSC_symlink fs/namei.c:4145 [inline]
SyS_symlink+0x7d/0x240 fs/namei.c:4143
do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 13422:
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
putname+0xee/0x130 fs/namei.c:258
SYSC_symlinkat fs/namei.c:4139 [inline]
SyS_symlinkat fs/namei.c:4112 [inline]
SYSC_symlink fs/namei.c:4145 [inline]
SyS_symlink+0x14e/0x240 fs/namei.c:4143
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 ffff88016552a180
which belongs to the cache names_cache of size 4096
The buggy address is located 128 bytes inside of
4096-byte region [ffff88016552a180, ffff88016552b180)
The buggy address belongs to the page:
page:ffffea0005954a80 count:1 mapcount:0 mapping:ffff88016552a180 index:0x0
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff88016552a180 0000000000000000 0000000100000001
raw: ffffea00051e2220 ffffea00050b1c20 ffff8801da5da600 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88016552a100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88016552a180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88016552a200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
^
ffff88016552a280: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88016552a300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.