Commit 03393fd5 authored Apr 22, 2013 by Wei Liu Committed by David S. Miller Apr 22, 2013

xen-netback: don't disconnect frontend when seeing oversize packet



Some frontend drivers are sending packets > 64 KiB in length. This length
overflows the length field in the first slot making the following slots have
an invalid length.

Turn this error back into a non-fatal error by dropping the packet. To avoid
having the following slots having fatal errors, consume all slots in the
packet.

This does not reopen the security hole in XSA-39 as if the packet as an
invalid number of slots it will still hit fatal error case.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 2810e5b9

drivers/net/xen-netback/netback.c

+16 −6

Original line number	Diff line number	Diff line
		@@ -975,12 +975,22 @@ static int netbk_count_requests(struct xenvif *vif,

		memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + slots),
		sizeof(*txp));
		if (txp->size > first->size) {
		netdev_err(vif->dev,

		/* If the guest submitted a frame >= 64 KiB then
		* first->size overflowed and following slots will
		* appear to be larger than the frame.
		*
		* This cannot be fatal error as there are buggy
		* frontends that do this.
		*
		* Consume all slots and drop the packet.
		*/
		if (!drop_err && txp->size > first->size) {
		if (net_ratelimit())
		netdev_dbg(vif->dev,
		"Invalid tx request, slot size %u > remaining size %u\n",
		txp->size, first->size);
		netbk_fatal_tx_err(vif);
		return -EIO;
		drop_err = -EIO;
		}

		first->size -= txp->size;