Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sriram Narasimhan , "Michael S. Tsirkin" , Jason Wang , "David S. Miller" Subject: [ 60/95] tuntap: forbid changing mq flag for persistent device Date: Tue, 25 Jun 2013 11:32:47 -0700 Message-Id: <20130625182200.392392501@linuxfoundation.org> In-Reply-To: <20130625182153.605455184@linuxfoundation.org> References: <20130625182153.605455184@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jason Wang [ Upstream commit 8e6d91ae0917bf934ed86411148f79d904728d51 ] 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 Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/net/tun.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1585,6 +1585,10 @@ static int tun_set_iff(struct net *net, 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);