linux-kernel - Re: PANIC: "Oops: 0000 [#1] PREEMPT SMP PTI" starting from 5.17 on dual socket Intel Xeon Gold servers

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YmGKrd1BR9HSEy6q@slm.duckdns.org>
Date:   Thu, 21 Apr 2022 06:47:41 -1000
From:   Tejun Heo <tj@...nel.org>
To:     Jirka Hladky <jhladky@...hat.com>
Cc:     Minchan Kim <minchan@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        regressions@...ts.linux.dev,
        Thorsten Leemhuis <regressions@...mhuis.info>,
        Justin Forbes <jforbes@...oraproject.org>
Subject: Re: PANIC: "Oops: 0000 [#1] PREEMPT SMP PTI" starting from 5.17 on
 dual socket Intel Xeon Gold servers

Sorry about late reply.

On Wed, Apr 20, 2022 at 10:02:20AM +0200, Jirka Hladky wrote:
> > Based on your report, kernel was crashed due to kn_mondata was NULL
> >
> >   rdt_kill_sb
> >     rmdir_all_sub
> >       ..
> >       kernfs_remove(kn_mondata);
> >         struct kernfs_root *root = kernfs_root(kn); <-- crashed
> >
> >
> > Before the my patch[1], it worked like this.
> >
> >   rdt_kill_sb
> >     rmdir_all_sub
> >       ..
> >       kernfs_remove(kn_mondata);
> >         down_write(&kernfs_rwsem);
> >           if (!kn)
> >             return;
> >         up_write(&kernfs_rwsem);
> >
> > IOW, before, kernfs_remove worked with NULL argument via just bailing
> > but with the my patch[1], it doesn't work any longer.
> >
> > It makes me have questions for kernfs maintainers:
> >
> > Should kernfs_remove API support NULL parameter? If so, can we support
> > it atomically without old global kernfs_rwsem?
> >
> > [1] 393c3714081a, kernfs: switch global kernfs_rwsem lock to per-fs lock

Yes, I mean, kernfs_remove() used to support NULL arg, so it should do the
same after the locking change too. Can you send a patch?

Thanks.

-- 
tejun