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Date:   Tue, 15 Mar 2022 20:25:51 +0800
From:   Gao Xiang <hsiangkao@linux.alibaba.com>
To:     Dongliang Mu <mudongliangabcd@gmail.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>
Subject: Re: [PATCH] fs: erofs: remember if kobject_init_and_add was done
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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> wrote:
> >
> > 在 2022/3/15 18:55, Gao Xiang 写道:
> > > On Tue, Mar 15, 2022 at 06:43:01PM +0800, Huang Jianan wrote:
> > >> 在 2022/3/15 15:51, Dongliang Mu 写道:
> > >>> 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 any 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 extra 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...

Thanks,
Gao Xiang