qeth: avoid buffer overflow in snmp ioctl

Check user-defined length in snmp ioctl request and allow request
only if it fits into a qeth command buffer.

Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Reviewed-by: Heiko Carstens <heicars2@linux.vnet.ibm.com>
Reported-by: Nico Golde <nico@ngolde.de>
Reported-by: Fabian Yamaguchi <fabs@goesec.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
static int qeth_clear_channels(struct qeth_card *card)
{
	int rc1 = 0, rc2 = 0, rc3 = 0;

	QETH_CARD_TEXT(card, 3, "clearchs");
	rc1 = qeth_clear_channel(&card->read);
	rc2 = qeth_clear_channel(&card->write);
	rc3 = qeth_clear_channel(&card->data);
	if (rc1)
		return rc1;
	if (rc2)
		return rc2;
	return rc3;
}

static int qeth_clear_channels(struct qeth_card *card)
{
	int rc1 = 0, rc2 = 0, rc3 = 0;

	QETH_CARD_TEXT(card, 3, "clearchs");
	rc1 = qeth_clear_channel(&card->read);
	rc2 = qeth_clear_channel(&card->write);
	rc3 = qeth_clear_channel(&card->data);
	if (rc1)
		return rc1;
	if (rc2)
		return rc2;
	return rc3;
}
