CVE-2026-90189

/// Technical description

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

null_blk: register configfs subsystem after creating default devices

In null_init(), configfs_register_subsystem() currently runs before

register_blkdev(), so when null_blk is built as a module, a racing mkdir()

+ poweron from userspace can reach null_add_dev() while null_major is still

0. __add_disk() then hits WARN_ON(disk->minors) (major=0 with minors!=0)

and fails:

[root@fedora ~]# [ 2366.521436] WARNING: block/genhd.c:476 at __add_disk+0x8a7/0xde0,

[ 2366.523552] Modules linked in: null_blk(+) nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib

[ 2366.529081] CPU: 26 UID: 0 PID: 1600 Comm: sh Not tainted 7.2.0-rc1+ #66 PREEMPT(full)

......

[ 2366.547251] Call Trace:

[ 2366.547575] <TASK>

[ 2366.547831] ? _raw_spin_lock+0x84/0xe0

[ 2366.548260] add_disk_fwnode+0x114/0x560

[ 2366.548739] null_add_dev+0x102d/0x1b80 [null_blk]

[ 2366.549310] ? __pfx_null_add_dev+0x10/0x10 [null_blk]

[ 2366.549906] ? mutex_lock+0xd

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References