staging: rtl8712: memory corruption in wpa_set_encryption()

->KeyMaterial is declared as a 16 byte array, but we only ever allocate
either 5 or 13 bytes of it.  The problem is that we memset() all 16
bytes to zero so we're memsetting past the end of the allocated memory.

I fixed this in slightly lazy way, by just allocating 16 bytes.  This
works but there is a lot more cleanup you could do to this code if you
wanted.  Which is why this code is in staging.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8712/rtl871x_ioctl_linux.c

@@ -398,12 +398,9 @@ static int wpa_set_encryption(struct net_device *dev, struct ieee_param *param,
 			wep_key_idx = 0;
 		if (wep_key_len > 0) {
 			wep_key_len = wep_key_len <= 5 ? 5 : 13;
-			pwep = kmalloc((u32)(wep_key_len +
-				FIELD_OFFSET(struct NDIS_802_11_WEP,
-				KeyMaterial)), GFP_ATOMIC);
+			pwep = kzalloc(sizeof(*pwep), GFP_ATOMIC);
 			if (pwep == NULL)
 				return -ENOMEM;
-			memset(pwep, 0, sizeof(struct NDIS_802_11_WEP));
 			pwep->KeyLength = wep_key_len;
 			pwep->Length = wep_key_len +
 				 FIELD_OFFSET(struct NDIS_802_11_WEP,