nfc: fix memory leak of se_io context in nfc_genl_se_io

The callback context for sending/receiving APDUs to/from the selected
secure element is allocated inside nfc_genl_se_io and supposed to be
eventually freed in se_io_cb callback function. However, there are several
error paths where the bwi_timer is not charged to call se_io_cb later, and
the cb_context is leaked.

The patch proposes to free the cb_context explicitly on those error paths.

At the moment we can't simply check 'dev->ops->se_io()' return value as it
may be negative in both cases: when the timer was charged and was not.

Fixes: 5ce3f32b52 ("NFC: netlink: SE API implementation")
Reported-by: syzbot+df64c0a2e8d68e78a4fa@syzkaller.appspotmail.com
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/nfc/st-nci/se.c

@@ -672,6 +672,12 @@ int st_nci_se_io(struct nci_dev *ndev, u32 se_idx,
 					ST_NCI_EVT_TRANSMIT_DATA, apdu,
 					apdu_length);
 	default:
+		/* Need to free cb_context here as at the moment we can't
+		 * clearly indicate to the caller if the callback function
+		 * would be called (and free it) or not. In both cases a
+		 * negative value may be returned to the caller.
+		 */
+		kfree(cb_context);
 		return -ENODEV;
 	}
 }

drivers/nfc/st21nfca/se.c

@@ -236,6 +236,12 @@ int st21nfca_hci_se_io(struct nfc_hci_dev *hdev, u32 se_idx,
 					ST21NFCA_EVT_TRANSMIT_DATA,
 					apdu, apdu_length);
 	default:
+		/* Need to free cb_context here as at the moment we can't
+		 * clearly indicate to the caller if the callback function
+		 * would be called (and free it) or not. In both cases a
+		 * negative value may be returned to the caller.
+		 */
+		kfree(cb_context);
 		return -ENODEV;
 	}
 }

net/nfc/netlink.c

@@ -1442,7 +1442,11 @@ static int nfc_se_io(struct nfc_dev *dev, u32 se_idx,
 	rc = dev->ops->se_io(dev, se_idx, apdu,
 			apdu_length, cb, cb_context);
 
+	device_unlock(&dev->dev);
+	return rc;
+
 error:
+	kfree(cb_context);
 	device_unlock(&dev->dev);
 	return rc;
 }