CVE-2026-90228: high-severity vulnerability in Linux

In the Linux kernel, the following vulnerability has been resolved: nvmet: fix NULL pointer dereference in nvmet_execute_identify_ns_zns() When a host issues an Identify command with CNS 05h (I/O Command Set specific Identify Namespace) and CSI 02h (ZNS) targeting a file-backed namespace, nvmet_execute_identify_ns_zns() calls bdev_is_zoned() on req->ns->bdev. A file-backed namespace has no block device, so req->ns->bdev is NULL and bdev_is_zoned() dereferences it, oopsing. The I/O command set is selected by the host-supplied CSI field and the command is routed here whenever CONFIG_BLK_DEV_ZONED is enabled, independent of the namespace backing type, so any file-backed namespace is exposed. Reject the command with Invalid Field when the namespace is not backed by a block device.