ccid: Fix buffer overrun in handling of VSC_ATR message

ATR size exceeding the limit is diagnosed, but then we merrily use it
anyway, overrunning card->atr[].

The message is read from a character device.  Obvious security
implications unless the other end of the character device is trusted.

Spotted by Coverity.  CVE-2011-4111.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/ccid-card-passthru.c

@@ -150,6 +150,7 @@ static void ccid_card_vscard_handle_message(PassthruState *card,
             error_report("ATR size exceeds spec, ignoring");
             ccid_card_vscard_send_error(card, scr_msg_header->reader_id,
                                         VSC_GENERAL_ERROR);
+            break;
         }
         memcpy(card->atr, data, scr_msg_header->length);
         card->atr_length = scr_msg_header->length;