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[79.177.145.168]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4995c7b2898sm99603235e9.4.2026.08.08.03.39.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 08 Aug 2026 03:39:12 -0700 (PDT) Date: Sat, 8 Aug 2026 06:39:09 -0400 From: "Michael S. Tsirkin" To: Jia Jia Cc: Jason Wang , Eugenio =?iso-8859-1?Q?P=E9rez?= , Tiwei Bie , kvm@vger.kernel.org, virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] vhost/vdpa: reject VRING_NUM larger than device max Message-ID: <20260808063901-mutt-send-email-mst@kernel.org> References: <20260808103415.101261-1-physicalmtea@gmail.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260808103415.101261-1-physicalmtea@gmail.com> On Sat, Aug 08, 2026 at 06:34:15PM +0800, Jia Jia wrote: > vhost_vring_set_num() only requires a non-zero power-of-two that fits > in 16 bits. vhost-vdpa then hands that value to the backend through > set_vq_num() without comparing it to get_vq_num_max(). > > A local process with access to /dev/vhost-vdpa-* can therefore set a > queue size larger than the device advertises. On the vdpa_sim backend, > the worker then walks descriptors beyond the mapped descriptor ring. > KASAN reports a 16-byte out-of-bounds read, corresponding to one > vring_desc, in the vringh IOTLB path: > > BUG: KASAN: out-of-bounds in _copy_from_iter > Read of size 16 > copy_from_iotlb > copydesc_iotlb > vringh_getdesc_iotlb > vdpasim_net_work > > Check the requested size against get_vq_num_max() in > vhost_vdpa_vring_ioctl() before calling vhost_vring_ioctl(), and return > -EINVAL when the request is too large. > > Fixes: 4c8cf31885f6 ("vhost: introduce vDPA-based backend") sign off missing > --- > drivers/vhost/vdpa.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c > index ac55275fa0d0..b2083e1ef150 100644 > --- a/drivers/vhost/vdpa.c > +++ b/drivers/vhost/vdpa.c > @@ -716,6 +716,13 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd, > vhost_vdpa_unsetup_vq_irq(v, idx); > } > break; > + case VHOST_SET_VRING_NUM: > + /* Reject sizes above the max reported by the device. */ > + if (copy_from_user(&s, argp, sizeof(s))) > + return -EFAULT; > + if (s.num > ops->get_vq_num_max(vdpa)) > + return -EINVAL; > + break; > } > > r = vhost_vring_ioctl(&v->vdev, cmd, argp); > -- > 2.34.1