[PATCH 3.10 103/129] ceph: fix null pointer dereference

[Greg Kroah-Hartman]

3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nathaniel Yazdani <n1ght.4nd.d4y@xxxxxxxxx>

commit c338c07c51e3106711fad5eb599e375eadb6855d upstream.

When register_session() is given an out-of-range argument for mds,
ceph_mdsmap_get_addr() will return a null pointer, which would be given to
ceph_con_open() & be dereferenced, causing a kernel oops. This fixes bug #4685
in the Ceph bug tracker <http://tracker.ceph.com/issues/4685>.

Signed-off-by: Nathaniel Yazdani <n1ght.4nd.d4y@xxxxxxxxx>
Reviewed-by: Sage Weil <sage@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/ceph/mds_client.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -414,6 +414,9 @@ static struct ceph_mds_session *register
 {
 	struct ceph_mds_session *s;
 
+	if (mds >= mdsc->mdsmap->m_max_mds)
+		return ERR_PTR(-EINVAL);
+
 	s = kzalloc(sizeof(*s), GFP_NOFS);
 	if (!s)
 		return ERR_PTR(-ENOMEM);


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