CVE-2026-45890

In the Linux kernel, the following vulnerability has been resolved:

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 (requestednumqueues > xenvifmaxqueues) but not zero, allowing requestednumqueues=0 to reach vzalloc(arraysize(0, sizeof(struct xenvifqueue))), which triggers WARNONONCE(!size) in __vmallocnoderange().

On systems with paniconwarn=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.