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

[Dongliang Mu]

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 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@xxxxxxxxx>
---
 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