linux-kernel - [PATCH 4.19 31/71] ceph: fix use-after-free for fsc->mdsc

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Date:   Mon, 24 Aug 2020 10:31:22 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+b57f46d8d6ea51960b8c@...kaller.appspotmail.com,
        Xiubo Li <xiubli@...hat.com>, Jeff Layton <jlayton@...nel.org>,
        Ilya Dryomov <idryomov@...il.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 31/71] ceph: fix use-after-free for fsc->mdsc

From: Xiubo Li <xiubli@...hat.com>

[ Upstream commit a7caa88f8b72c136f9a401f498471b8a8e35370d ]

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

Reported-by: syzbot+b57f46d8d6ea51960b8c@...kaller.appspotmail.com
Signed-off-by: Xiubo Li <xiubli@...hat.com>
Reviewed-by: Jeff Layton <jlayton@...nel.org>
Signed-off-by: Ilya Dryomov <idryomov@...il.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/ceph/mds_client.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index a2e903203bf9f..0fa14d8b9c64c 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -3682,7 +3682,6 @@ int ceph_mdsc_init(struct ceph_fs_client *fsc)
 		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);
@@ -3723,6 +3722,8 @@ int ceph_mdsc_init(struct ceph_fs_client *fsc)
 
 	strscpy(mdsc->nodename, utsname()->nodename,
 		sizeof(mdsc->nodename));
+
+	fsc->mdsc = mdsc;
 	return 0;
 }
 
-- 
2.25.1