linux-kernel - Re: [syzbot] [reiserfs?] INFO: task hung in flush_old

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Date:   Wed, 24 May 2023 17:50:03 +0200
From:   Roberto Sassu <roberto.sassu@...weicloud.com>
To:     Paul Moore <paul@...l-moore.com>,
        linux-security-module@...r.kernel.org
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        reiserfs-devel@...r.kernel.org, roberto.sassu@...wei.com,
        syzkaller-bugs@...glegroups.com,
        syzbot <syzbot+0a684c061589dcc30e51@...kaller.appspotmail.com>
Subject: Re: [syzbot] [reiserfs?] INFO: task hung in flush_old_commits

On Wed, 2023-05-24 at 11:11 -0400, Paul Moore wrote:
> On Wed, May 24, 2023 at 5:59 AM syzbot
> <syzbot+0a684c061589dcc30e51@...kaller.appspotmail.com> wrote:
> > syzbot has bisected this issue to:
> > 
> > commit d82dcd9e21b77d338dc4875f3d4111f0db314a7c
> > Author: Roberto Sassu <roberto.sassu@...wei.com>
> > Date:   Fri Mar 31 12:32:18 2023 +0000
> > 
> >     reiserfs: Add security prefix to xattr name in reiserfs_security_write()
> > 
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=11c39639280000
> > start commit:   421ca22e3138 Merge tag 'nfs-for-6.4-2' of git://git.linux-..
> > git tree:       upstream
> > final oops:     https://syzkaller.appspot.com/x/report.txt?x=13c39639280000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=15c39639280000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=7d8067683055e3f5
> > dashboard link: https://syzkaller.appspot.com/bug?extid=0a684c061589dcc30e51
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14312791280000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12da8605280000
> > 
> > Reported-by: syzbot+0a684c061589dcc30e51@...kaller.appspotmail.com
> > Fixes: d82dcd9e21b7 ("reiserfs: Add security prefix to xattr name in reiserfs_security_write()")
> > 
> > For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> 
> Roberto, I think we need to resolve this somehow.  As I mentioned
> earlier, I don't believe this to be a fault in your patch, rather that
> patch simply triggered a situation that had not been present before,
> likely because the reiserfs code always failed when writing LSM
> xattrs.  Regardless, we still need to fix the deadlocks that sysbot
> has been reporting.

Hi Paul

ok, I will try.

Roberto

> Has anyone dug into the reiserfs code to try and resolve the deadlock?
>  Considering the state of reiserfs, I'm guessing no one has, and I
> can't blame them; I personally would have a hard time justifying
> significant time spent on reiserfs at this point.  Unless someone has
> any better ideas, I'm wondering if we shouldn't just admit defeat with
> reiserfs and LSM xattrs and disable/remove the reiserfs LSM xattr
> support?  Given the bug that Roberto was fixing with the patch in
> question, it's unlikely this was working anyway.
> 
> --
> paul-moore.com