[PATCH] ceph: fix null pointer dereference

From: Nathaniel Yazdani
Date: Mon Aug 05 2013 - 00:05:18 EST

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>
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 187bf21..ddff072 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -414,6 +414,9 @@ static struct ceph_mds_session *register_session(struct ceph_mds_client *mdsc,
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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