From: Xiubo Li <xiubli@redhat.com>
Date: Thu, 23 Jul 2020 15:32:25 +0800
Subject: ceph: fix use-after-free for fsc->mdsc
Git-commit: a7caa88f8b72c136f9a401f498471b8a8e35370d
Patch-mainline: v5.9-rc1
References: bsc#1177043

If the ceph_mdsc_init() fails, it will free the mdsc already.

Reported-by: syzbot+b57f46d8d6ea51960b8c@syzkaller.appspotmail.com
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Acked-by: Luis Henriques <lhenriques@suse.com>
---
 fs/ceph/mds_client.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -3870,7 +3870,6 @@ int ceph_mdsc_init(struct ceph_fs_client
 		return -ENOMEM;
 	}
 
-	fsc->mdsc = mdsc;
 	init_completion(&mdsc->safe_umount_waiters);
 	init_waitqueue_head(&mdsc->session_close_wq);
 	INIT_LIST_HEAD(&mdsc->waiting_for_map);
@@ -3912,6 +3911,8 @@ int ceph_mdsc_init(struct ceph_fs_client
 
 	strscpy(mdsc->nodename, utsname()->nodename,
 		sizeof(mdsc->nodename));
+
+	fsc->mdsc = mdsc;
 	return 0;
 }