KASAN: invalid-free in path_openat

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: d2f0c961 ipv4: ip_do_fragment: Preserve skb_iif during fra..
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=159de4fca00000
kernel config: https://syzkaller.appspot.com/x/.config?x=a42d110b47dd6b36
dashboard link: https://syzkaller.appspot.com/bug?extid=b85f8220acd82f921d99
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
CC: [linux-...@vger.kernel.org linux-...@vger.kernel.org
vi...@zeniv.linux.org.uk net...@vger.kernel.org]

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+b85f82...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: double-free or invalid-free in kfree_link+0x16/0x20
fs/libfs.c:1105

CPU: 0 PID: 6289 Comm: blkid Not tainted 5.1.0-rc6+ #191
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
kasan_report_invalid_free+0x65/0xa0 mm/kasan/report.c:278
__kasan_slab_free+0x13a/0x150 mm/kasan/common.c:438
kasan_slab_free+0xe/0x10 mm/kasan/common.c:467
__cache_free mm/slab.c:3499 [inline]
kfree+0xcf/0x230 mm/slab.c:3822
kfree_link+0x16/0x20 fs/libfs.c:1105
do_delayed_call include/linux/delayed_call.h:28 [inline]
put_link fs/namei.c:881 [inline]
step_into fs/namei.c:1770 [inline]
do_last fs/namei.c:3381 [inline]
path_openat+0x1ca1/0x46e0 fs/namei.c:3533
do_filp_open+0x1a1/0x280 fs/namei.c:3563
do_sys_open+0x3fe/0x5d0 fs/open.c:1069
__do_sys_open fs/open.c:1087 [inline]
__se_sys_open fs/open.c:1082 [inline]
__x64_sys_open+0x7e/0xc0 fs/open.c:1082
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f4cfc81c120
Code: 48 8b 15 1b 4d 2b 00 f7 d8 64 89 02 83 c8 ff c3 90 90 90 90 90 90 90
90 90 90 83 3d d5 a4 2b 00 00 75 10 b8 02 00 00 00 0f 05 <48> 3d 01 f0 ff
ff 73 31 c3 48 83 ec 08 e8 5e 8c 01 00 48 89 04 24
RSP: 002b:00007ffec5df8748 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007ffec5df9790 RCX: 00007f4cfc81c120
RDX: 00007ffec5df8762 RSI: 0000000000000000 RDI: 00007ffec5df8750
RBP: 0000000000000703 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffec5dfa808
R13: 0000000000000000 R14: 00007f4cfccfd820 R15: 00007f4cfcaf32a2

Allocated by task 0:
(stack is not available)

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8880a620c540
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 2240 bytes inside of
4096-byte region [ffff8880a620c540, ffff8880a620d540)
The buggy address belongs to the page:
page:ffffea0002988300 count:1 mapcount:0 mapping:ffff88812c3f0dc0
index:0xffff8880a620d340 compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffff88809ac2ae38 ffff88809ac2ae38 ffff88812c3f0dc0
raw: ffff8880a620d340 ffff8880a620c540 00000001fffffff2 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a620cd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a620cd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8880a620ce00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
^
ffff8880a620ce80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8880a620cf00: 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.