fs: erofs: add sanity check for kobject in erofs_unregister_sysfs

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.

Link: https://lore.kernel.org/r/20220315132814.12332-1-dzm91@hust.edu.cn
Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
Fixes: 168e9a76200c ("erofs: add sysfs interface")
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
index dac252b..f3babf1 100644 (file)
--- 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)