Re: [PATCH] fs: erofs: remember if kobject_init_and_add was done

[Huang Jianan]

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@xxxxxxxxx>
> > >
> > > 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@xxxxxxxxxxxxxxxx>
> > > Signed-off-by: Dongliang Mu <mudongliangabcd@xxxxxxxxx>
> > > ---
> > >    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.

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)