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vhost: fix total length when packets are too short

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When mergeable buffers are disabled, and the
incoming packet is too large for the rx buffer,
get_rx_bufs returns success.

This was intentional in order for make recvmsg
truncate the packet and then handle_rx would
detect err != sock_len and drop it.

Unfortunately we pass the original sock_len to
recvmsg - which means we use parts of iov not fully
validated.

Fix this up by detecting this overrun and doing packet drop
immediately.

CVE-2014-0077

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Michael S. Tsirkin 2014-03-27 12:00:26 +02:00 committed by David S. Miller
parent 05efa8c943
commit d8316f3991
1 changed files with 14 additions and 0 deletions
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14
drivers/vhost/net.c
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@ -532,6 +532,12 @@ static int get_rx_bufs(struct vhost_virtqueue *vq,
*iovcount = seg; *iovcount = seg;
if (unlikely(log)) if (unlikely(log))
*log_num = nlogs; *log_num = nlogs;
/* Detect overrun */
if (unlikely(datalen > 0)) {
r = UIO_MAXIOV + 1;
goto err;
}
return headcount; return headcount;
err: err:
vhost_discard_vq_desc(vq, headcount); vhost_discard_vq_desc(vq, headcount);
@ -587,6 +593,14 @@ static void handle_rx(struct vhost_net *net)
/* On error, stop handling until the next kick. */ /* On error, stop handling until the next kick. */
if (unlikely(headcount < 0)) if (unlikely(headcount < 0))
break; break;
/* On overrun, truncate and discard */
if (unlikely(headcount > UIO_MAXIOV)) {
msg.msg_iovlen = 1;
err = sock->ops->recvmsg(NULL, sock, &msg,
1, MSG_DONTWAIT | MSG_TRUNC);
pr_debug("Discarded rx packet: len %zd\n", sock_len);
continue;
}
/* OK, now we need to know about added descriptors. */ /* OK, now we need to know about added descriptors. */
if (!headcount) { if (!headcount) {
if (unlikely(vhost_enable_notify(&net->dev, vq))) { if (unlikely(vhost_enable_notify(&net->dev, vq))) {