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: 8d3d53b3e433 ("xen-netback: Add support for multiple queues") Signed-off-by: Ziyi Guo --- drivers/net/xen-netback/xenbus.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c index a78a25b87240..2ef59b08ae21 100644 --- a/drivers/net/xen-netback/xenbus.c +++ b/drivers/net/xen-netback/xenbus.c @@ -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; } -- 2.34.1