From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id 70CE643F01 for ; Thu, 25 Apr 2024 15:44:43 +0200 (CEST) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 66550435F4; Thu, 25 Apr 2024 15:44:43 +0200 (CEST) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by mails.dpdk.org (Postfix) with ESMTP id 499C940284 for ; Thu, 25 Apr 2024 15:44:42 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1714052681; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=Nq3OJKOONSkNhh2+TnUs4BN4NAh/7c2GuKEjUsJAHVc=; b=UandrU4Bs0jalGREVydMgkFIn9i92+r7TrPTjuEFA41y3y82GQpNReyKzSzKUxBRdkcsw0 T4LlkTNR+R1pVLKC6Fbbnl1C+DEmo+dGvvIyKbtmMzmvYtA5XbJ+s61vAKXEBmX3qDM/aq 3Kggbtqej341vIEaOT2+ItcfygcbiJM= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-221-NP9XbV8wPwmav5kDpEi3aw-1; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-BeenThere: stable@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: patches for DPDK stable branches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: stable-bounces@dpdk.org On 4/10/24 17:21, Luca Vizzarro wrote: > This patch resolves a build error with GCC 13 and arm/aarch32 as > targets: > > In function ‘mbuf_to_desc’, > inlined from ‘vhost_enqueue_async_packed’ at > ../lib/vhost/virtio_net.c:1828:6, > inlined from ‘virtio_dev_rx_async_packed’ at > ../lib/vhost/virtio_net.c:1842:6, > inlined from ‘virtio_dev_rx_async_submit_packed’ at > ../lib/vhost/virtio_net.c:1900:7: > ../lib/vhost/virtio_net.c:1159:18: error: ‘buf_vec[0].buf_addr’ may > be used uninitialized [-Werror=maybe-uninitialized] > 1159 | buf_addr = buf_vec[vec_idx].buf_addr; > | ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~ > > ../lib/vhost/virtio_net.c:1160:18: error: ‘buf_vec[0].buf_iova’ may > be used uninitialized [-Werror=maybe-uninitialized] > 1160 | buf_iova = buf_vec[vec_idx].buf_iova; > | ~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~ > > ../lib/vhost/virtio_net.c:1161:35: error: ‘buf_vec[0].buf_len’ may > be used uninitialized [-Werror=maybe-uninitialized] > 1161 | buf_len = buf_vec[vec_idx].buf_len; > | ~~~~~~~~~~~~~~~~^~~~~~~~ > > GCC complains about the possible runtime path where the while loop > which fills buf_vec (in vhost_enqueue_async_packed) is not run. As a > consequence it correctly thinks that buf_vec is not initialized while > being accessed anyways. > > This scenario is actually very unlikely as the only way this can occur > is if size has overflowed to 0. Meaning that the total packet length > would be close to UINT64_MAX (or actually UINT32_MAX). At first glance, > the code suggests that this may never happen as the type of size has > been changed to 64-bit. For a 32-bit architecture such as arm > (e.g. armv7-a) and aarch32, this still happens because the operand types > (pkt->pkt_len and sizeof) are 32-bit wide, performing 32-bit arithmetic > first (where the overflow can happen) and widening to 64-bit later. > > The proposed fix simply guarantees to the compiler that the scope which > fills buf_vec is accessed at least once, while not disrupting the actual > logic. This is based on the assumption that size will always be greater > than 0, as suggested by the sizeof, and the packet length will never be > as big as UINT32_MAX, and causing an overflow. > > Fixes: 873e8dad6f49 ("vhost: support packed ring in async datapath") > Cc: stable@dpdk.org > > Signed-off-by: Luca Vizzarro > Reviewed-by: Paul Szczepanek > Reviewed-by: Nick Connolly > --- > lib/vhost/virtio_net.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > Reviewed-by: Maxime Coquelin Thanks, Maxime