From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Tan, Jianfeng" Subject: Re: [PATCH] net/virtio-user: fix cannot get initialized Date: Thu, 13 Apr 2017 10:18:43 +0800 Message-ID: <5e7b5876-0f98-9c42-965e-e91b318cd17f@intel.com> References: <1491551860-15005-1-git-send-email-jianfeng.tan@intel.com> <20170413015812.GE7333@yliu-dev.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: dev@dpdk.org, Maxime Coquelin To: Yuanhan Liu Return-path: Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by dpdk.org (Postfix) with ESMTP id 6B3692C23 for ; Thu, 13 Apr 2017 04:18:46 +0200 (CEST) In-Reply-To: <20170413015812.GE7333@yliu-dev.sh.intel.com> Content-Language: en-US List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 4/13/2017 9:58 AM, Yuanhan Liu wrote: > On Fri, Apr 07, 2017 at 07:57:40AM +0000, Jianfeng Tan wrote: >> After the introduction of vhost MTU, VIRTIO_NET_F_MTU is enabled >> by default. However, virtio-user vtpci does not support to get >> MTU from device yet, i.e., vtpci_read_dev_config(MTU) fails. >> Plus, struct virtio_net_config is defined as a uninitialized >> variable, and could be different values in >> virtio_negotiate_features() and virtio_init_device(). >> >> In some cases, it passes the check in virtio_negotiate_features() >> but fails the check in virtio_init_device(). As a result, >> virtio-user canno be initialized. >> >> To fix it, (1) accessing uninitialized variable is not a good >> practice, so initialize it as zero; (2) explicitly disable MTU >> feature in virtio-user. >> >> Fixes: 49d26d9e3f47 ("net/virtio: support MTU feature") >> Cc: Maxime Coquelin >> Cc: Yuanhan Liu >> >> Signed-off-by: Jianfeng Tan >> --- >> drivers/net/virtio/virtio_ethdev.c | 4 ++-- >> drivers/net/virtio/virtio_user/virtio_user_dev.c | 6 ++++++ >> 2 files changed, 8 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/net/virtio/virtio_ethdev.c b/drivers/net/virtio/virtio_ethdev.c >> index 78cb3e8..4c43784 100644 >> --- a/drivers/net/virtio/virtio_ethdev.c >> +++ b/drivers/net/virtio/virtio_ethdev.c >> @@ -1163,7 +1163,7 @@ virtio_negotiate_features(struct virtio_hw *hw, uint64_t req_features) >> >> /* If supported, ensure MTU value is valid before acknowledging it. */ >> if (host_features & req_features & (1ULL << VIRTIO_NET_F_MTU)) { >> - struct virtio_net_config config; >> + struct virtio_net_config config = {0}; > virtio-user does not support the MTU feature, this patch should not be > reached. The virtio-user feature negotiation should be broken. > > --yliu > Yes, it will not come to here anyway. But some static code analyzer might report this as an error: there's chance to read uninitialized variable. Thanks, Jianfeng