From mboxrd@z Thu Jan 1 00:00:00 1970 From: Amit Shah Subject: [PATCH 4/9] virtio-serial: Handle scatter-gather buffers for control messages Date: Fri, 19 Mar 2010 17:28:41 +0530 Message-ID: <1268999926-29560-5-git-send-email-amit.shah@redhat.com> References: <1268999926-29560-1-git-send-email-amit.shah@redhat.com> <1268999926-29560-2-git-send-email-amit.shah@redhat.com> <1268999926-29560-3-git-send-email-amit.shah@redhat.com> <1268999926-29560-4-git-send-email-amit.shah@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1268999926-29560-4-git-send-email-amit.shah@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: qemu-devel@nongnu.org Cc: quintela@redhat.com, mst@redhat.com, virtualization@lists.linux-foundation.org, Avi Kivity , Amit Shah List-Id: virtualization@lists.linuxfoundation.org Current control messages are small enough to not be split into multiple buffers but we could run into such a situation in the future or a malicious guest could cause such a situation. So handle the entire iov request for control messages. Also ensure the size of the control request is >= what we expect otherwise we risk accessing memory that we don't own. Signed-off-by: Amit Shah CC: Avi Kivity Reported-by: Avi Kivity --- hw/virtio-serial-bus.c | 43 ++++++++++++++++++++++++++++++++++++++++--- 1 files changed, 40 insertions(+), 3 deletions(-) diff --git a/hw/virtio-serial-bus.c b/hw/virtio-serial-bus.c index 830eb75..d5887ab 100644 --- a/hw/virtio-serial-bus.c +++ b/hw/virtio-serial-bus.c @@ -200,7 +200,7 @@ size_t virtio_serial_guest_ready(VirtIOSerialPort *port) } /* Guest wants to notify us of some event */ -static void handle_control_message(VirtIOSerial *vser, void *buf) +static void handle_control_message(VirtIOSerial *vser, void *buf, size_t len) { struct VirtIOSerialPort *port; struct virtio_console_control cpkt, *gcpkt; @@ -208,6 +208,10 @@ static void handle_control_message(VirtIOSerial *vser, void *buf) size_t buffer_len; gcpkt = buf; + if (len < sizeof(cpkt)) { + /* The guest sent an invalid control packet */ + return; + } port = find_port_by_id(vser, ldl_p(&gcpkt->id)); if (!port) return; @@ -281,12 +285,45 @@ static void control_out(VirtIODevice *vdev, VirtQueue *vq) { VirtQueueElement elem; VirtIOSerial *vser; + uint8_t *buf; + size_t len; vser = DO_UPCAST(VirtIOSerial, vdev, vdev); + len = 0; + buf = NULL; while (virtqueue_pop(vq, &elem)) { - handle_control_message(vser, elem.out_sg[0].iov_base); - virtqueue_push(vq, &elem, elem.out_sg[0].iov_len); + unsigned int i; + size_t cur_len, offset; + + cur_len = 0; + for (i = 0; i < elem.out_num; i++) { + cur_len += elem.out_sg[i].iov_len; + } + /* + * Allocate a new buf only if we didn't have one previously or + * if the size of the buf differs + */ + if (cur_len != len) { + if (len) { + qemu_free(buf); + } + buf = qemu_malloc(cur_len); + } + + offset = 0; + for (i = 0; i < elem.out_num; i++) { + memcpy(buf + offset, elem.out_sg[i].iov_base, + elem.out_sg[i].iov_len); + offset += elem.out_sg[i].iov_len; + } + len = cur_len; + + handle_control_message(vser, buf, len); + virtqueue_push(vq, &elem, len); + } + if (len) { + qemu_free(buf); } virtio_notify(vdev, vq); } -- 1.6.2.5