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[79.34.249.199]) by smtp.gmail.com with ESMTPSA id f17sm34650125wrv.0.2021.02.02.07.49.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 02 Feb 2021 07:49:52 -0800 (PST) Date: Tue, 2 Feb 2021 16:49:50 +0100 From: Stefano Garzarella To: Stefan Hajnoczi Cc: virtualization@lists.linux-foundation.org, Xie Yongji , "Michael S. Tsirkin" , Laurent Vivier , linux-kernel@vger.kernel.org, Max Gurtovoy , Jason Wang , kvm@vger.kernel.org Subject: Re: [PATCH RFC v2 08/10] vdpa: add vdpa simulator for block device Message-ID: <20210202154950.g3rclpigyaigzfgo@steredhat> References: <20210128144127.113245-1-sgarzare@redhat.com> <20210128144127.113245-9-sgarzare@redhat.com> <20210202093412.GA243557@stefanha-x1.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20210202093412.GA243557@stefanha-x1.localdomain> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 02, 2021 at 09:34:12AM +0000, Stefan Hajnoczi wrote: >On Thu, Jan 28, 2021 at 03:41:25PM +0100, Stefano Garzarella wrote: >> +static void vdpasim_blk_work(struct work_struct *work) >> +{ >> + struct vdpasim *vdpasim = container_of(work, struct vdpasim, work); >> + u8 status = VIRTIO_BLK_S_OK; >> + int i; >> + >> + spin_lock(&vdpasim->lock); >> + >> + if (!(vdpasim->status & VIRTIO_CONFIG_S_DRIVER_OK)) >> + goto out; >> + >> + for (i = 0; i < VDPASIM_BLK_VQ_NUM; i++) { >> + struct vdpasim_virtqueue *vq = &vdpasim->vqs[i]; >> + >> + if (!vq->ready) >> + continue; >> + >> + while (vringh_getdesc_iotlb(&vq->vring, &vq->out_iov, >> + &vq->in_iov, &vq->head, >> + GFP_ATOMIC) > 0) { >> + int write; >> + >> + vq->in_iov.i = vq->in_iov.used - 1; >> + write = vringh_iov_push_iotlb(&vq->vring, &vq->in_iov, >> + &status, 1); >> + if (write <= 0) >> + break; > >This code looks fragile: > >1. Relying on unsigned underflow and the while loop in > vringh_iov_push_iotlb() to handle the case where in_iov.used == 0 is > risky and could break. > >2. Does this assume that the last in_iov element has size 1? For > example, the guest driver may send a single "in" iovec with size 513 > when reading 512 bytes (with an extra byte for the request status). > >Please validate inputs fully, even in test/development code, because >it's likely to be copied by others when writing production code (or >deployed in production by unsuspecting users) :). Perfectly agree on that, so I addressed these things, also following your review on the previous version, on the next patch of this series: "vdpa_sim_blk: implement ramdisk behaviour". Do you think should I move these checks in this patch? I did this to leave Max credit for this patch and add more code to emulate a ramdisk in later patches. Thanks, Stefano