UBUNTU-CVE-2026-90187: Low severity ubuntu/linux-hwe-edge vulnerability

In the Linux kernel, the following vulnerability has been resolved: nullblk: free zones array on device power-off nullinitzoneddev() allocates dev->zones when a zoned device is powered on, but nulldeldev() never frees it on power-off; dev->zones is only freed later in nullfreedev(), when the configfs directory is removed. If the device is powered off and then on again, nullinitzoneddev() allocates a new array and overwrites the dev->zones pointer, leaking the previous allocation each power cycle. Free dev->zones in nulldeldev() via nullfreezoneddev() to solve it. And calling nullfreezoneddev() in nullfreedev() is no longer necessary because every caller already invokes nulldeldev() first: via nullbgroupdropitem() before nullbdevicerelease(), in the nulladddev() error path of nullcreatedev(), and in nulldestroydev(). Remove the redundant call. And take &lock around zonecondstore() in the two store wrappers to serialize dev->zones check-and-deref against its alloc/free, which already run under &lock. The reason there was no problem before is that only nullbdevicerelease() or nullexit() frees the dev->zones, which guarantees that subsequent users won't access the configfs interface.