Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <3192BC90-D082-472B-B310-6E09A14A77C6@hust.edu.cn>
 <CAD-N9QUqfq+0UeMjQALUmGpX5xgjS6=BXvsqcXQpJRzhB6hHLw@mail.gmail.com>
 <CAKFNMokdB+Zph-1OyC1-Xnyi93r+yKSusgaEaa=CkuUBttwRZA@mail.gmail.com>
 <CAD-N9QU8-Od3G+-=RHM5K7vR2-4Af+4t=XutJJVdmkKhH7OarA@mail.gmail.com>
 <CAKFNMo=E8mMuY7Et0auH02fOzGKx04k2=LOj8mZJ6a-=J+sPzQ@mail.gmail.com>
 <CAD-N9QWt=d2Vj2bevSzOPL4AWF08_zTyq=hHOcOOROCazNY4_A@mail.gmail.com>
 <CAD-N9QWrBLygN24EC6QLRFF6uf7=PiTRdA4suKqEXJ7tk9aocA@mail.gmail.com>
 <dac7104a-21ac-24f4-6132-e51960fa0b7e@gmail.com> <CAKFNMon3=fFWtuUa1_wDyK9agpCXjbzA8b+rj=OYu=7Gs8nMqQ@mail.gmail.com>
 <7da316f4-aa65-896e-9020-2dfff2bbfc09@gmail.com> <CAKFNMon7cdJ092Ppne_kU6A23pRUb+1tThCkoB2vn0HN-rWUUg@mail.gmail.com>
 <CAD-N9QXN_DEmoqTEpFdCp=Gne1O3U=+8WpwjP638wbUn1Vb6hA@mail.gmail.com> <CAD-N9QVcSnboZqS7tXgU_iD8zzg5a_ubB3W2qtCFequS5u6jqQ@mail.gmail.com>
In-Reply-To: <CAD-N9QVcSnboZqS7tXgU_iD8zzg5a_ubB3W2qtCFequS5u6jqQ@mail.gmail.com>
From:   Ryusuke Konishi <konishi.ryusuke@gmail.com>
Date:   Tue, 15 Mar 2022 13:46:44 +0900
Message-ID: <CAKFNMo=uYDbrwDpqeehbdT5va3X1yw5uBoec1q8AoNAADtrELw@mail.gmail.com>
Subject: Re: Fw:Re: [PATCH] fs: nilfs2: fix memory leak in nilfs sysfs create
 device group
To:     Dongliang Mu <mudongliangabcd@gmail.com>
Cc:     Pavel Skripkin <paskripkin@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-nilfs <linux-nilfs@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Nanyong Sun <sunnanyong@huawei.com>,
        =?UTF-8?B?5oWV5Yas5Lqu?= <dzm91@hust.edu.cn>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Tue, Mar 15, 2022 at 10:59 AM Dongliang Mu <mudongliangabcd@gmail.com> wrote:
>
> On Sun, Mar 13, 2022 at 9:35 PM Dongliang Mu <mudongliangabcd@gmail.com> wrote:
> >
> > On Sun, Mar 13, 2022 at 12:01 AM Ryusuke Konishi
> > <konishi.ryusuke@gmail.com> wrote:
> > >
> > > Hi Pavel and Dongliang,
> > >
> > > On Sun, Mar 13, 2022 at 12:16 AM Pavel Skripkin <paskripkin@gmail.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
>
> Hi Ryusuke,
>
> The crash still occurred in my newly set up syzkaller instance. It
> appears after two days' fuzzing.
>
> I remember you suggested me to add kobject_del just for testing,
> right? And let's see if this crash still occurs any more.

You need a few days to reproduce it ?
If so, I think this confirmation method is uncertain.
In that case, I will try inserting an artificial error by changing
nilfs_sysfs_create_device_group() a bit to confirm if the same crash occurs.

Ryusuke Konishi