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

Dongliang Mu
2022-03-15T12:00:01Z

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.

> 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)
>