WARNING in reconnect_path

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 775d01b6 Linux 4.14.154
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13b86426e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=90a13857da9a45b6
dashboard link: https://syzkaller.appspot.com/bug?extid=465415c9633d5fbe6f01
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12fa6a1ce00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12da3ffce00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+465415...@syzkaller.appspotmail.com

RDX: 0000000000400000 RSI: 0000000020000000 RDI: 00000000ffffff9c
RBP: 0000000000000000 R08: 0000000000000002 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000009e82
R13: 0000000000000005 R14: 00007ffd6bd2df50 R15: 0000000000000000
------------[ cut here ]------------
WARNING: CPU: 0 PID: 6865 at fs/exportfs/expfs.c:96 clear_disconnected
fs/exportfs/expfs.c:96 [inline]
WARNING: CPU: 0 PID: 6865 at fs/exportfs/expfs.c:96
reconnect_path+0x4a6/0x630 fs/exportfs/expfs.c:232
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 6865 Comm: syz-executor304 Not tainted 4.14.154 #0
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+0x142/0x197 lib/dump_stack.c:58
panic+0x1f9/0x42d kernel/panic.c:183
__warn.cold+0x2f/0x2f kernel/panic.c:547
report_bug+0x216/0x254 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:177 [inline]
fixup_bug arch/x86/kernel/traps.c:172 [inline]
do_error_trap+0x1bb/0x310 arch/x86/kernel/traps.c:295
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:314
invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:963
RIP: 0010:clear_disconnected fs/exportfs/expfs.c:96 [inline]
RIP: 0010:reconnect_path+0x4a6/0x630 fs/exportfs/expfs.c:232
RSP: 0018:ffff888092807bf0 EFLAGS: 00010297
RAX: ffff8880935a41c0 RBX: dffffc0000000000 RCX: 1ffff110126b4946
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8880941b3e00
RBP: ffff888092807c40 R08: ffff8880935a41c0 R09: 0000000000000000
R10: 0000000000000000 R11: ffff8880935a41c0 R12: ffff8880941b3dc0
R13: dffffc0000000000 R14: ffff8880941b3dc0 R15: ffff8880991e1820
exportfs_decode_fh+0x3cc/0x5e2 fs/exportfs/expfs.c:448
do_handle_to_path fs/fhandle.c:153 [inline]
handle_to_path fs/fhandle.c:208 [inline]
do_handle_open+0x285/0x640 fs/fhandle.c:224
SYSC_open_by_handle_at fs/fhandle.c:266 [inline]
SyS_open_by_handle_at+0x27/0x30 fs/fhandle.c:257
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x441b29
RSP: 002b:00007ffd6bd2def8 EFLAGS: 00000246 ORIG_RAX: 0000000000000130
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000441b29
RDX: 0000000000400000 RSI: 0000000020000000 RDI: 00000000ffffff9c
RBP: 0000000000000000 R08: 0000000000000002 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000009e82
R13: 0000000000000005 R14: 00007ffd6bd2df50 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

[syzbot]

syzbot has bisected this bug to:

commit e41d58185f1444368873d4d7422f7664a68be61d
Author: Dmitry Vyukov <dvy...@google.com>
Date: Wed Jul 12 21:34:35 2017 +0000

fault-inject: support systematic fault injection

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13131116e00000
start commit: 775d01b6 Linux 4.14.154
git tree: linux-4.14.y
final crash: https://syzkaller.appspot.com/x/report.txt?x=10931116e00000
console output: https://syzkaller.appspot.com/x/log.txt?x=17131116e00000

kernel config: https://syzkaller.appspot.com/x/.config?x=90a13857da9a45b6
dashboard link: https://syzkaller.appspot.com/bug?extid=465415c9633d5fbe6f01

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12fa6a1ce00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12da3ffce00000

Reported-by: syzbot+465415...@syzkaller.appspotmail.com
Fixes: e41d58185f14 ("fault-inject: support systematic fault injection")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[syzbot]

syzbot suspects this bug was fixed by commit:

commit b6e209a13a61b65848e214319e3348e5e23346cb
Author: YueHaibing <yueha...@huawei.com>
Date: Mon Nov 19 03:32:41 2018 +0000

exportfs: fix 'passing zero to ERR_PTR()' warning

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13d271d9e00000
start commit: 775d01b6 Linux 4.14.154
git tree: linux-4.14.y

kernel config: https://syzkaller.appspot.com/x/.config?x=90a13857da9a45b6
dashboard link: https://syzkaller.appspot.com/bug?extid=465415c9633d5fbe6f01

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12fa6a1ce00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12da3ffce00000

If the result looks correct, please mark the bug fixed by replying with:

#syz fix: exportfs: fix 'passing zero to ERR_PTR()' warning