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From:   Dongliang Mu <mudongliangabcd@gmail.com>
Date:   Tue, 15 Mar 2022 21:30:46 +0800
Message-ID: <CAD-N9QUERu_ZurAyACT+rKnPLp8ZFGDcifENLufT2sq1N9tzoQ@mail.gmail.com>
Subject: Re: [PATCH] fs: erofs: remember if kobject_init_and_add was done
To:     Gao Xiang <hsiangkao@linux.alibaba.com>
Cc:     Huang Jianan <jnhuang95@gmail.com>,
        Dongliang Mu <dzm91@hust.edu.cn>, Gao Xiang <xiang@kernel.org>,
        Chao Yu <chao@kernel.org>,
        syzkaller <syzkaller@googlegroups.com>,
        linux-erofs@lists.ozlabs.org,
        linux-kernel <linux-kernel@vger.kernel.org>
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On Tue, Mar 15, 2022 at 8:44 PM Dongliang Mu <mudongliangabcd@gmail.com> wr=
ote:
>
> On Tue, Mar 15, 2022 at 8:26 PM Gao Xiang <hsiangkao@linux.alibaba.com> w=
rote:
> >
> > Hi Dongliang,
> >
> > On Tue, Mar 15, 2022 at 07:59:26PM +0800, Dongliang Mu wrote:
> > > On Tue, Mar 15, 2022 at 7:05 PM Huang Jianan <jnhuang95@gmail.com> wr=
ote:
> > > >
> > > > =E5=9C=A8 2022/3/15 18:55, Gao Xiang =E5=86=99=E9=81=93:
> > > > > On Tue, Mar 15, 2022 at 06:43:01PM +0800, Huang Jianan wrote:
> > > > >> =E5=9C=A8 2022/3/15 15:51, Dongliang Mu =E5=86=99=E9=81=93:
> > > > >>> From: Dongliang Mu <mudongliangabcd@gmail.com>
> > > > >>>
> > > > >>> Syzkaller hit 'WARNING: kobject bug in erofs_unregister_sysfs'.=
 This bug
> > > > >>> is triggered by injecting fault in kobject_init_and_add of
> > > > >>> erofs_unregister_sysfs.
> > > > >>>
> > > > >>> Fix this by remembering if kobject_init_and_add is successful.
> > > > >>>
> > > > >>> Note that I've tested the patch and the crash does not occur an=
y more.
> > > > >>>
> > > > >>> Reported-by: syzkaller <syzkaller@googlegroups.com>
> > > > >>> Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
> > > > >>> ---
> > > > >>>    fs/erofs/internal.h | 1 +
> > > > >>>    fs/erofs/sysfs.c    | 9 ++++++---
> > > > >>>    2 files changed, 7 insertions(+), 3 deletions(-)
> > > > >>>
> > > > >>> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> > > > >>> index 5aa2cf2c2f80..9e20665e3f68 100644
> > > > >>> --- a/fs/erofs/internal.h
> > > > >>> +++ b/fs/erofs/internal.h
> > > > >>> @@ -144,6 +144,7 @@ struct erofs_sb_info {
> > > > >>>     u32 feature_incompat;
> > > > >>>     /* sysfs support */
> > > > >>> +   bool s_sysfs_inited;
> > > > >> Hi Dongliang,
> > > > >>
> > > > >> How about using sbi->s_kobj.state_in_sysfs to avoid adding a ext=
ra member in
> > > > >> sbi ?
> > > > > Ok, I have no tendency of these (I'm fine with either ways).
> > > > > I've seen some usage like:
> > > > >
> > > > > static inline int device_is_registered(struct device *dev)
> > > > > {
> > > > >          return dev->kobj.state_in_sysfs;
> > > > > }
> > > > >
> > > > > But I'm still not sure if we need to rely on such internal
> > > > > interface.. More thoughts?
> > > >
> > > > Yeah... It seems that it is better to use some of the interfaces
> > > > provided by kobject,
> > > > otherwise we should still maintain this state in sbi.
> > > >
> > >
> > > I am fine with either way. Let me know if you reach to an agreement.
> >
> > If you have time, would you mind sending another patch by using
> > state_in_sysfs? I'd like to know Chao's perference later, and
> > apply one of them...
>
> OK, let me test this patch in my local workspace. If it works, I will
> send it later.

Hi Gao Xiang,

I've sent another patch. Please double-check.

>
> >
> > Thanks,
> > Gao Xiang
> >