linux-kernel - Re: [PATCH] fs: erofs: remember if kobject_init_and

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Message-ID: <CAD-N9QX2cajf0LXKcOji_Em26-0bw9wfhx7KDV_TLDWhgQ90hQ@mail.gmail.com>
Date:   Tue, 15 Mar 2022 19:59:26 +0800
From:   Dongliang Mu <mudongliangabcd@...il.com>
To:     Huang Jianan <jnhuang95@...il.com>
Cc:     Gao Xiang <hsiangkao@...ux.alibaba.com>,
        Dongliang Mu <dzm91@...t.edu.cn>, Gao Xiang <xiang@...nel.org>,
        Chao Yu <chao@...nel.org>,
        syzkaller <syzkaller@...glegroups.com>,
        linux-erofs@...ts.ozlabs.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fs: erofs: remember if kobject_init_and_add was done

On Tue, Mar 15, 2022 at 7:05 PM Huang Jianan <jnhuang95@...il.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@...il.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@...glegroups.com>
> >>> Signed-off-by: Dongliang Mu <mudongliangabcd@...il.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.

> Thanks,
> Jianan
>
> > Thanks,
> > Gao Xiang
> >> Thanks,
> >> Jianan
> >>
> >>>     struct kobject s_kobj;          /* /sys/fs/erofs/<devname> */
> >>>     struct completion s_kobj_unregister;
> >>>    };
> >>> diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
> >>> index dac252bc9228..2b48a4df19b4 100644
> >>> --- a/fs/erofs/sysfs.c
> >>> +++ b/fs/erofs/sysfs.c
> >>> @@ -209,6 +209,7 @@ int erofs_register_sysfs(struct super_block *sb)
> >>>                                "%s", sb->s_id);
> >>>     if (err)
> >>>             goto put_sb_kobj;
> >>> +   sbi->s_sysfs_inited = true;
> >>>     return 0;
> >>>    put_sb_kobj:
> >>> @@ -221,9 +222,11 @@ void erofs_unregister_sysfs(struct super_block *sb)
> >>>    {
> >>>     struct erofs_sb_info *sbi = EROFS_SB(sb);
> >>> -   kobject_del(&sbi->s_kobj);
> >>> -   kobject_put(&sbi->s_kobj);
> >>> -   wait_for_completion(&sbi->s_kobj_unregister);
> >>> +   if (sbi->s_sysfs_inited) {
> >>> +           kobject_del(&sbi->s_kobj);
> >>> +           kobject_put(&sbi->s_kobj);
> >>> +           wait_for_completion(&sbi->s_kobj_unregister);
> >>> +   }
> >>>    }
> >>>    int __init erofs_init_sysfs(void)
>