Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751655AbbDMFkF (ORCPT ); Mon, 13 Apr 2015 01:40:05 -0400 Received: from ozlabs.org ([103.22.144.67]:36104 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751067AbbDMFkC (ORCPT ); Mon, 13 Apr 2015 01:40:02 -0400 From: David Gibson To: anton@au.ibm.com, benh@kernel.crashing.org, michael@ellerman.id.au Cc: linuxppc-dev@vger.kernel.org, linux-kernel@vger.kernel.org, David Gibson Subject: [PATCH] ibmveth: Fix off-by-one error in ibmveth_change_mtu() Date: Mon, 13 Apr 2015 15:39:46 +1000 Message-Id: <1428903586-21442-1-git-send-email-david@gibson.dropbear.id.au> X-Mailer: git-send-email 2.1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1769 Lines: 41 AFAIK the PAPR document which defines the virtual device interface used by the ibmveth driver doesn't specify a specific maximum MTU. So, in the ibmveth driver, the maximum allowed MTU is determined by the maximum allocated buffer size of 64k (corresponding to one page in the common case) minus the per-buffer overhead IBMVETH_BUFF_OH (which has value 22 for 14 bytes of ethernet header, plus 8 bytes for an opaque handle). This suggests a maximum allowable MTU of 65514 bytes, but in fact the driver only permits a maximum MTU of 65513. This is because there is a < instead of an <= in ibmveth_change_mtu(), which only permits an MTU which is strictly smaller than the buffer size, rather than allowing the buffer to be completely filled. This patch fixes the buglet. Signed-off-by: David Gibson --- drivers/net/ethernet/ibm/ibmveth.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/ethernet/ibm/ibmveth.c b/drivers/net/ethernet/ibm/ibmveth.c index cd7675a..3aa280a 100644 --- a/drivers/net/ethernet/ibm/ibmveth.c +++ b/drivers/net/ethernet/ibm/ibmveth.c @@ -1257,7 +1257,7 @@ static int ibmveth_change_mtu(struct net_device *dev, int new_mtu) for (i = 0; i < IBMVETH_NUM_BUFF_POOLS; i++) { adapter->rx_buff_pool[i].active = 1; - if (new_mtu_oh < adapter->rx_buff_pool[i].buff_size) { + if (new_mtu_oh <= adapter->rx_buff_pool[i].buff_size) { dev->mtu = new_mtu; vio_cmo_set_dev_desired(viodev, ibmveth_get_desired_dma -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/