Re: [PATCH net] xen-netback: reject zero-queue configuration from guest

[Jürgen Groß]

On 12.02.26 23:40, Ziyi Guo wrote:
> 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 <n7l8m4@xxxxxxxxxxxxxxxxxx>

Reviewed-by: Juergen Gross <jgross@xxxxxxxx>


Juergen

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