[bug report] NFC: st21nfca: Fix some skb memory leaks

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Christophe Ricard,

The patch c490c557b67f: "NFC: st21nfca: Fix some skb memory leaks"
from Jan 25, 2015, leads to the following static checker warning:

	drivers/nfc/st21nfca/core.c:742 st21nfca_hci_complete_target_discovered()
	warn: 'nfcid_skb' was already freed.

drivers/nfc/st21nfca/core.c
   712                          /* NFC Forum Digital Protocol Table 44 */
   713                          if (target->sensf_res[0] == 0x01 &&
   714                              target->sensf_res[1] == 0xfe)
   715                                  target->supported_protocols =
   716                                                          NFC_PROTO_NFC_DEP_MASK;
   717                          else
   718                                  target->supported_protocols =
   719                                                          NFC_PROTO_FELICA_MASK;
   720                  } else {
   721                          kfree_skb(nfcid_skb);
                                ^^^^^^^^^^^^^^^^^^^^
Freed.

   722                          /* P2P in type A */
   723                          r = nfc_hci_get_param(hdev, ST21NFCA_RF_READER_F_GATE,
   724                                          ST21NFCA_RF_READER_F_NFCID1,
   725                                          &nfcid_skb);
                                                ^^^^^^^^^^
This is set to a different new skb on some error paths but if we return
-EADDRNOTAVAIL then it's still the same freed skb.

   726                          if (r < 0)
   727                                  goto exit;
                                        ^^^^^^^^^
We hit this goto and double free.

   728  
   729                          if (nfcid_skb->len > NFC_NFCID1_MAXSIZE) {
   730                                  r = -EPROTO;
   731                                  goto exit;
   732                          }
   733                          memcpy(target->sensf_res, nfcid_skb->data,
   734                                  nfcid_skb->len);
   735                          target->sensf_res_len = nfcid_skb->len;
   736                          target->supported_protocols = NFC_PROTO_NFC_DEP_MASK;
   737                  }
   738                  target->hci_reader_gate = ST21NFCA_RF_READER_F_GATE;
   739          }
   740          r = 1;
   741  exit:
   742          kfree_skb(nfcid_skb);
   743          return r;
   744  }

regards,
dan carpenter