From mboxrd@z Thu Jan 1 00:00:00 1970 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) Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 12 Apr 2017 19:18:45 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.37,192,1488873600"; d="scan'208";a="247992323" Received: from shwdeisgchi083.ccr.corp.intel.com (HELO [10.239.67.137]) ([10.239.67.137]) by fmsmga004.fm.intel.com with ESMTP; 12 Apr 2017 19:18:44 -0700 To: Yuanhan Liu Cc: dev@dpdk.org, Maxime Coquelin References: <1491551860-15005-1-git-send-email-jianfeng.tan@intel.com> <20170413015812.GE7333@yliu-dev.sh.intel.com> From: "Tan, Jianfeng" Message-ID: <5e7b5876-0f98-9c42-965e-e91b318cd17f@intel.com> Date: Thu, 13 Apr 2017 10:18:43 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.0 MIME-Version: 1.0 In-Reply-To: <20170413015812.GE7333@yliu-dev.sh.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Subject: Re: [dpdk-dev] [PATCH] net/virtio-user: fix cannot get initialized X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 13 Apr 2017 02:18:46 -0000 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