CVE-2026-90189

CVE CVE-2026-90189EUVD EUVD-2026-81782Published 2026-09-17T16:07:10.000Z

What the advisory describes

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+0xde/0x1c0 [ 2366.550361] ? __pfx_mutex_lock+0x10/0x10 [ 2366.550827] nullb_device_power_store+0x1e7/0x280 [null_blk] [ 2366.551499] ? __pfx_nullb_device_power_store+0x10/0x10 [null_blk] [ 2366.552177] ? __kmalloc_cache_noprof+0x1f5/0x470 [ 2366.552748] ? configfs_write_iter+0x35c/0x4e0 [ 2366.553242] configfs_write_iter+0x286/0x4e0 [ 2366.553787] vfs_write+0x52d/0xd00 [ 2366.554169] ? __pfx_vfs_write+0x10/0x10 [ 2366.554679] ? __pfx___css_rstat_updated+0x10/0x10 [ 2366.555196] ? fdget_pos+0x1cf/0x4c0 [ 2366.555649] ksys_write+0xfc/0x1d0 ...... Additionally, the err_dev path destroys all devices on nullb_list while configfs is still registered. If a racing mkdir() + poweron puts a user device on the list, null_destroy_dev()->null_free_dev() kfrees the user device's nullb_device but /sys/kernel/config/nullb/<name> is still reachable. Any userspace access to the item will trigger a UAF. For simplicity, move configfs_register_subsystem() to the end to solve the problems above.

Source: EUVD (ENISA), in the words of the advisory.

Products the advisory names

These come from the advisory itself, not from any check we performed.

• Linux — Linux patch: 7.3-rc1; 3bf2bd20734e3e6ffda53719a9c10fb3ee9c5ffa <d761be1b8f2bbabc41252deb79a426d3f0d4fa10; 3bf2bd20734e3e6ffda53719a9c10fb3ee9c5ffa <2679b11e9256bd70a5ef41783bab6ad6c34a3db1; patch: 6.1.188; patch: 7.2.6; 3bf2bd20734e3e6ffda53719a9c10fb3ee9c5ffa <dbcedbe4819ae21274ea77469e61e46a878b9943; patch: 6.6.157; 4.14; 3bf2bd20734e3e6ffda53719a9c10fb3ee9c5ffa <c9d293d6bb0575fcb1f3408129453187e2a28a4e; patch: 6.12.110; 3bf2bd20734e3e6ffda53719a9c10fb3ee9c5ffa <cab9bf5f68f76cd44e0ec92bd4a60c9b83656a36; patch: 6.18.52; 3bf2bd20734e3e6ffda53719a9c10fb3ee9c5ffa <57debc907aef66319d244009d3370dcd97388d37; patch: 0

The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.

Carried in the product catalogue

An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.

• Linux — Linux

Patchlage reports hits and suspected hits. About everything else this system says nothing — neither this page nor the situation report ever claims that an estate is safe.