Re: [syzbot] [fs?] general protection fault in grab_requested_root

[Qing Wang]

#syz test

diff --git a/fs/namespace.c b/fs/namespace.c
index a67cbe42746d..eb7d2774ee1c 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -5678,13 +5678,16 @@ static int do_statmount(struct kstatmount *s, u64 mnt_id, u64 mnt_ns_id,
 
 		s->mnt = mnt_file->f_path.mnt;
 		ns = real_mount(s->mnt)->mnt_ns;
-		if (!ns)
+		if (IS_ERR(ns))
+			return PTR_ERR(ns);
+		if (!ns) {
 			/*
 			 * We can't set mount point and mnt_ns_id since we don't have a
 			 * ns for the mount. This can happen if the mount is unmounted
 			 * with MNT_DETACH.
 			 */
 			s->mask &= ~(STATMOUNT_MNT_POINT | STATMOUNT_MNT_NS_ID);
+		}
 	} else {
 		/* Has the namespace already been emptied? */
 		if (mnt_ns_id && mnt_ns_empty(ns))