linux-kernel - Re: Fw:Re: [PATCH] fs: nilfs2: fix memory leak in nilfs sysfs create device group

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Message-ID: <CAD-N9QXN_DEmoqTEpFdCp=Gne1O3U=+8WpwjP638wbUn1Vb6hA@mail.gmail.com>
Date:   Sun, 13 Mar 2022 21:35:25 +0800
From:   Dongliang Mu <mudongliangabcd@...il.com>
To:     Ryusuke Konishi <konishi.ryusuke@...il.com>
Cc:     Pavel Skripkin <paskripkin@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-nilfs <linux-nilfs@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Nanyong Sun <sunnanyong@...wei.com>,
        慕冬亮 <dzm91@...t.edu.cn>
Subject: Re: Fw:Re: [PATCH] fs: nilfs2: fix memory leak in nilfs sysfs create
 device group

On Sun, Mar 13, 2022 at 12:01 AM Ryusuke Konishi
<konishi.ryusuke@...il.com> wrote:
>
> Hi Pavel and Dongliang,
>
> On Sun, Mar 13, 2022 at 12:16 AM Pavel Skripkin <paskripkin@...il.com> wrote:
> >
> > Hi Ryusuke,
> >
> > On 3/12/22 18:11, Ryusuke Konishi wrote:
> > >> In case of nilfs_attach_log_writer() error code jumps to
> > >> failed_checkpoint label and calls destroy_nilfs() which should call
> > >> nilfs_sysfs_delete_device_group().
> > >
> > > nilfs_sysfs_delete_device_group() is called in destroy_nilfs()
> > > if nilfs->ns_flags has THE_NILFS_INIT flag -- nilfs_init() inline
> > > function tests this flag.
> > >
> > > The flag is set after init_nilfs() succeeded at the beginning of
> > > nilfs_fill_super() because the set_nilfs_init() inline in init_nilfs() sets it.
> > >
> > > So,  nilfs_sysfs_delete_group() seems to be called in case of
> > > the above failure.   Am I missing something?
> > >
> >
> > Yeah, that's what I mean :) I can't see how reported issue is possible
> > with current code.
> >
> >
> > Sorry for not being clear
>
> Understood, thanks for the reply.
>
> If so,  the case where nilfs_sysfs_create_device_group() itself failed,
> is suspicious as mentioned in the previous mail.   A possible scenario
> I guess is :
>
> - nilfs_sysfs_create_device_group() on the first mount try fails and leaks
>   due to lack of kobject_del() in the error path.
> - Then, nilfs_sysfs_create_device_group() on the next mount try hits
>   the leak detector at kobject_init_and_add().
>
> So, if the leak bug is reproducible, I'd like to ask Dongliang to
> test the effect of the first patch.

If my local syzkaller instance gets a reproducer, I will try to do this.

>
> Regards,
> Ryusuke Konishi
>
> >
> >
> >
> > With regards,
> > Pavel Skripkin