From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752562Ab3E2EmX (ORCPT ); Wed, 29 May 2013 00:42:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36503 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750955Ab3E2EmW (ORCPT ); Wed, 29 May 2013 00:42:22 -0400 From: Jason Wang To: davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Jason Wang , "Michael S. Tsirkin" Subject: [PATCH] tuntap: forbid changing mq flag for persistent device Date: Wed, 29 May 2013 12:32:11 +0800 Message-Id: <1369801931-6856-1-git-send-email-jasowang@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We currently allow changing the mq flag (IFF_MULTI_QUEUE) for a persistent device. This will result a mismatch between the number the queues in netdev and tuntap. This is because we only allocate a 1q netdevice when IFF_MULTI_QUEUE was not specified, so when we set the IFF_MULTI_QUEUE and try to attach more queues later, netif_set_real_num_tx_queues() may fail which result a single queue netdevice with multiple sockets attached. Solve this by disallowing changing the mq flag for persistent device. Bug was introduced by commit edfb6a148ce62e5e19354a1dcd9a34e00815c2a1 (tuntap: reduce memory using of queues). Reported-by: Sriram Narasimhan Cc: Michael S. Tsirkin Signed-off-by: Jason Wang --- drivers/net/tun.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index f042b03..89776c5 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1585,6 +1585,10 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr) else return -EINVAL; + if (!!(ifr->ifr_flags & IFF_MULTI_QUEUE) != + !!(tun->flags & TUN_TAP_MQ)) + return -EINVAL; + if (tun_not_capable(tun)) return -EPERM; err = security_tun_dev_open(tun->security); -- 1.7.1