rbd: Fix use after free in rbd_open()

Commit a9ccedc3 frees the QemuOpts for the driver-specific options
immediately, even though it still needs the filename string that is
contained there. This doesn't work. Move the deletion of the QemuOpts to
the end of the function where its content isn't needed any more.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

block/rbd.c

@@ -478,20 +478,20 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict *options, int flags)
     }
 
     filename = qemu_opt_get(opts, "filename");
-    qemu_opts_del(opts);
 
     if (qemu_rbd_parsename(filename, pool, sizeof(pool),
                            snap_buf, sizeof(snap_buf),
                            s->name, sizeof(s->name),
                            conf, sizeof(conf)) < 0) {
-        return -EINVAL;
+        r = -EINVAL;
+        goto failed_opts;
     }
 
     clientname = qemu_rbd_parse_clientname(conf, clientname_buf);
     r = rados_create(&s->cluster, clientname);
     if (r < 0) {
         error_report("error initializing");
-        return r;
+        goto failed_opts;
     }
 
     s->snap = NULL;
@@ -557,6 +557,7 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict *options, int flags)
                             NULL, qemu_rbd_aio_flush_cb, s);
 
 
+    qemu_opts_del(opts);
     return 0;
 
 failed:
@@ -566,6 +567,8 @@ failed_open:
 failed_shutdown:
     rados_shutdown(s->cluster);
     g_free(s->snap);
+failed_opts:
+    qemu_opts_del(opts);
     return r;
 }