ae44674949
commit e2412c07f8f3040593dfb88207865a3cd58680c0 upstream.
When the rx buffer is too small for a packet, we will discard the vq
descriptor and retry it for the next packet:
while ((sock_len = vhost_net_rx_peek_head_len(net, sock->sk,
&busyloop_intr))) {
...
/* On overrun, truncate and discard */
if (unlikely(headcount > UIO_MAXIOV)) {
iov_iter_init(&msg.msg_iter, READ, vq->iov, 1, 1);
err = sock->ops->recvmsg(sock, &msg,
1, MSG_DONTWAIT | MSG_TRUNC);
pr_debug("Discarded rx packet: len %zd\n", sock_len);
continue;
}
...
}
This makes it possible to trigger a infinite while..continue loop
through the co-opreation of two VMs like:
1) Malicious VM1 allocate 1 byte rx buffer and try to slow down the
vhost process as much as possible e.g using indirect descriptors or
other.
2) Malicious VM2 generate packets to VM1 as fast as possible
Fixing this by checking against weight at the end of RX and TX
loop. This also eliminate other similar cases when:
- userspace is consuming the packets in the meanwhile
- theoretical TOCTOU attack if guest moving avail index back and forth
to hit the continue after vhost find guest just add new buffers
This addresses CVE-2019-3900.
Fixes: d8316f3991d20 ("vhost: fix total length when packets are too short")
Fixes: 3a4d5c94e9593 ("vhost_net: a kernel-level virtio server")
Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Balbir Singh <sblbir@amzn.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.