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

Gao Xiang
2022-03-15T10:56:01Z

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?

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)