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[79.27.201.176]) by smtp.gmail.com with ESMTPSA id c4sm8699628wrp.85.2020.10.08.13.24.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Oct 2020 13:24:38 -0700 (PDT) Date: Thu, 8 Oct 2020 22:24:36 +0200 From: Stefano Garzarella To: "Michael S. Tsirkin" Cc: netdev@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Rusty Russell , stable@vger.kernel.org, Jason Wang Subject: Re: [PATCH] vringh: fix __vringh_iov() when riov and wiov are different Message-ID: <20201008202436.r33jqbbttqynfvhe@steredhat> References: <20201008161311.114398-1-sgarzare@redhat.com> <20201008160035-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201008160035-mutt-send-email-mst@kernel.org> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Oct 08, 2020 at 04:00:51PM -0400, Michael S. Tsirkin wrote: > On Thu, Oct 08, 2020 at 06:13:11PM +0200, Stefano Garzarella wrote: > > If riov and wiov are both defined and they point to different > > objects, only riov is initialized. If the wiov is not initialized > > by the caller, the function fails returning -EINVAL and printing > > "Readable desc 0x... after writable" error message. > > > > Let's replace the 'else if' clause with 'if' to initialize both > > riov and wiov if they are not NULL. > > > > As checkpatch pointed out, we also avoid crashing the kernel > > when riov and wiov are both NULL, replacing BUG() with WARN_ON() > > and returning -EINVAL. > > > > Fixes: f87d0fbb5798 ("vringh: host-side implementation of virtio rings.") > > Cc: stable@vger.kernel.org > > Signed-off-by: Stefano Garzarella > > Can you add more detail please? when does this trigger? I'm developing vdpa_sim_blk and I'm using vringh_getdesc_iotlb() to get readable and writable buffers. With virtio-blk devices a descriptors has both readable and writable buffers (eg. virtio_blk_outhdr in the readable buffer and status as last byte of writable buffer). So, I'm calling vringh_getdesc_iotlb() one time to get both type of buffer and put them in 2 iovecs: ret = vringh_getdesc_iotlb(&vq->vring, &vq->riov, &vq->wiov, &vq->head, GFP_ATOMIC); With this patch applied it works well, without the function fails returning -EINVAL and printing "Readable desc 0x... after writable". Am I using vringh_getdesc_iotlb() in the wrong way? Thanks, Stefano > > > --- > > drivers/vhost/vringh.c | 9 +++++---- > > 1 file changed, 5 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c > > index e059a9a47cdf..8bd8b403f087 100644 > > --- a/drivers/vhost/vringh.c > > +++ b/drivers/vhost/vringh.c > > @@ -284,13 +284,14 @@ __vringh_iov(struct vringh *vrh, u16 i, > > desc_max = vrh->vring.num; > > up_next = -1; > > > > + /* You must want something! */ > > + if (WARN_ON(!riov && !wiov)) > > + return -EINVAL; > > + > > if (riov) > > riov->i = riov->used = 0; > > - else if (wiov) > > + if (wiov) > > wiov->i = wiov->used = 0; > > - else > > - /* You must want something! */ > > - BUG(); > > > > for (;;) { > > void *addr; > > -- > > 2.26.2 >