libceph: fix crush_decode() call site in osdmap_decode()

The size of the memory area feeded to crush_decode() should be limited
not only by osdmap end, but also by the crush map length.  Also, drop
unnecessary dout() (dout() in crush_decode() conveys the same info) and
step past crush map only if it is decoded successfully.

Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>

net/ceph/osdmap.c

@@ -802,16 +802,13 @@ static int osdmap_decode(void **p, void *end, struct ceph_osdmap *map)
 
 	/* crush */
 	ceph_decode_32_safe(p, end, len, e_inval);
-	dout("osdmap_decode crush len %d from off 0x%x\n", len,
+	map->crush = crush_decode(*p, min(*p + len, end));
-	     (int)(*p - start));
-	ceph_decode_need(p, end, len, e_inval);
-	map->crush = crush_decode(*p, end);
-	*p += len;
 	if (IS_ERR(map->crush)) {
 		err = PTR_ERR(map->crush);
 		map->crush = NULL;
 		goto bad;
 	}
+	*p += len;
 
 	/* ignore the rest */
 	*p = end;