[PATCH] fs: erofs: add sanity check for kobject in erofs_unregister_sysfs

[Gao Xiang]

On Tue, Mar 15, 2022 at 09:28:14PM +0800, Dongliang Mu wrote:
> From: Dongliang Mu <mudongliangabcd at 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 adding sanity check for kobject in erofs_unregister_sysfs
> 
> Note that I've tested the patch and the crash does not occur any more.
> 
> Signed-off-by: Dongliang Mu <mudongliangabcd at gmail.com>

Reviewed-by: Gao Xiang <hsiangkao at linux.alibaba.com>

Thanks,
Gao Xiang

> ---
>  fs/erofs/sysfs.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
> index dac252bc9228..f3babf1e6608 100644
> --- a/fs/erofs/sysfs.c
> +++ b/fs/erofs/sysfs.c
> @@ -221,9 +221,11 @@ 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_kobj.state_in_sysfs) {
> +		kobject_del(&sbi->s_kobj);
> +		kobject_put(&sbi->s_kobj);
> +		wait_for_completion(&sbi->s_kobj_unregister);
> +	}
>  }
>  
>  int __init erofs_init_sysfs(void)
> -- 
> 2.25.1