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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Thu, 25 Nov 2021 12:23:02 +0100
Message-ID: <CACT4Y+bJ4Ap74hBOBg7WMNDvhkjE2soD4MZ267gGP11G6s7Dsw@mail.gmail.com>
Subject: Re: [syzbot] WARNING in inc_nlink (2)
To:     Miklos Szeredi <miklos@szeredi.hu>
Cc:     syzbot <syzbot+1c8034b9f0e640f9ba45@syzkaller.appspotmail.com>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        Miklos Szeredi <mszeredi@redhat.com>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Al Viro <viro@zeniv.linux.org.uk>
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On Wed, 17 Nov 2021 at 08:25, Miklos Szeredi <miklos@szeredi.hu> wrote:
>
> On Wed, 17 Nov 2021 at 06:32, syzbot
> <syzbot+1c8034b9f0e640f9ba45@syzkaller.appspotmail.com> wrote:
> >
> > syzbot suspects this issue was fixed by commit:
> >
> > commit 97f044f690bac2b094bfb7fb2d177ef946c85880
> > Author: Miklos Szeredi <mszeredi@redhat.com>
> > Date:   Fri Oct 22 15:03:02 2021 +0000
> >
> >     fuse: don't increment nlink in link()
> >
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10563ac9b00000
> > start commit:   1da38549dd64 Merge tag 'nfsd-5.15-3' of git://git.kernel.o..
> > git tree:       upstream
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=e2ffb281e6323643
> > dashboard link: https://syzkaller.appspot.com/bug?extid=1c8034b9f0e640f9ba45
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11f16d57300000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15758d57300000
> >
> > If the result looks correct, please mark the issue as fixed by replying with:
>
> Highly unlikely: the original report was for sysvfs and the fix is for fuse.

Hi Miklos,

The fuse bug was folded into this report (on the dashboard you can see
examples of reports in fuse).
This is unavoidable for bugs that are left unaddressed for long. They
become piles of assorted stuff.

Now the best course of action is to mark it as fixed. Or we will
exacerbate the problem even more: it will be a bug about sysvfs, this
fuse bug, and the next similar bug in fuse and bugs in other file
systems.

#syz fix: fuse: don't increment nlink in link()