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[79.34.249.199]) by smtp.gmail.com with ESMTPSA id c9sm5443636wmb.33.2021.02.04.00.02.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Feb 2021 00:02:25 -0800 (PST) Date: Thu, 4 Feb 2021 09:02:23 +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: <20210204080223.rkc7zieq34ofs5ku@steredhat> References: <20210128144127.113245-1-sgarzare@redhat.com> <20210128144127.113245-9-sgarzare@redhat.com> <20210202093412.GA243557@stefanha-x1.localdomain> <20210202154950.g3rclpigyaigzfgo@steredhat> <20210203164551.GG74271@stefanha-x1.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20210203164551.GG74271@stefanha-x1.localdomain> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 03, 2021 at 04:45:51PM +0000, Stefan Hajnoczi wrote: >On Tue, Feb 02, 2021 at 04:49:50PM +0100, Stefano Garzarella wrote: >> 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. > >You could update the commit description so it's clear that input >validation is missing and will be added in the next commit. I'll do it. Thanks, Stefano