Commit 6d1dc801 authored by Ziyi Guo's avatar Ziyi Guo Committed by Paolo Abeni
Browse files

xen-netback: reject zero-queue configuration from guest 



A malicious or buggy Xen guest can write "0" to the xenbus key
"multi-queue-num-queues". The connect() function in the backend only
validates the upper bound (requested_num_queues > xenvif_max_queues)
but not zero, allowing requested_num_queues=0 to reach
vzalloc(array_size(0, sizeof(struct xenvif_queue))), which triggers
WARN_ON_ONCE(!size) in __vmalloc_node_range().

On systems with panic_on_warn=1, this allows a guest-to-host denial
of service.

The Xen network interface specification requires
the queue count to be "greater than zero".

Add a zero check to match the validation already present
in xen-blkback, which has included this
guard since its multi-queue support was added.

Fixes: 8d3d53b3 ("xen-netback: Add support for multiple queues")
Signed-off-by: default avatarZiyi Guo <n7l8m4@u.northwestern.edu>
Reviewed-by: default avatarJuergen Gross <jgross@suse.com>
Link: https://patch.msgid.link/20260212224040.86674-1-n7l8m4@u.northwestern.edu


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 9e7021d2

drivers/net/xen-netback/xenbus.c

+3 −2
Original line number Diff line number Diff line
@@ -735,10 +735,11 @@ static void connect(struct backend_info *be) 
	 */

	requested_num_queues = xenbus_read_unsigned(dev->otherend,

					"multi-queue-num-queues", 1);

	if (requested_num_queues > xenvif_max_queues) {

	if (requested_num_queues > xenvif_max_queues ||

	    requested_num_queues == 0) {

		/* buggy or malicious guest */

		xenbus_dev_fatal(dev, -EINVAL,

				 "guest requested %u queues, exceeding the maximum of %u.",

				 "guest requested %u queues, but valid range is 1 - %u.",

				 requested_num_queues, xenvif_max_queues);

		return;

	}