[patch 2/2] libceph: potential NULL dereference in ceph_osdc_handle_map()

There are two places where we read "nr_maps" if both of them are set to
zero then we would hit a NULL dereference here.

Signed-off-by: Dan Carpenter <redacted>
---
I think this is a real bug, but please review my fix for it because I'm
not very familiar with this code.

diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index 559a832..56f1fe5 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c

@@ -1786,6 +1786,8 @@ void ceph_osdc_handle_map(struct ceph_osd_client *osdc, struct ceph_msg *msg)
 		nr_maps--;
 	}
 
+	if (!osdc->osdmap)
+		goto bad;
 done:
 	downgrade_write(&osdc->map_sem);
 	ceph_monc_got_osdmap(&osdc->client->monc, osdc->osdmap->epoch);