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virtio-serial: Handle scatter-gather buffers for control messages

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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 <amit.shah@redhat.com>
CC: Avi Kivity <avi@redhat.com>
Reported-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Amit Shah 2010-04-27 18:04:07 +05:30 committed by Anthony Liguori
parent fa6111f215
commit e61da14d60
1 changed files with 28 additions and 3 deletions
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31
hw/virtio-serial-bus.c
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@ -204,7 +204,7 @@ 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;
@ -213,6 +213,11 @@ static void handle_control_message(VirtIOSerial *vser, void *buf)
gcpkt = buf;
if (len < sizeof(cpkt)) {
/* The guest sent an invalid control packet */
return;
}
cpkt.event = lduw_p(&gcpkt->event);
cpkt.value = lduw_p(&gcpkt->value);
@ -306,13 +311,33 @@ 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);
size_t cur_len, copied;
cur_len = iov_size(elem.out_sg, elem.out_num);
/*
* Allocate a new buf only if we didn't have one previously or
* if the size of the buf differs
*/
if (cur_len > len) {
qemu_free(buf);
buf = qemu_malloc(cur_len);
len = cur_len;
}
copied = iov_to_buf(elem.out_sg, elem.out_num, buf, 0, len);
handle_control_message(vser, buf, copied);
virtqueue_push(vq, &elem, copied);
}
qemu_free(buf);
virtio_notify(vdev, vq);
}