null_blk: register configfs subsystem after creating default devices

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-90189
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-17 17:17:13 UTC
Updated2026-09-17 17:17:13 UTC
DescriptionIn 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.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 3bf2bd20734e3e6ffda53719a9c10fb3ee9c5ffa 2679b11e9256bd70a5ef41783bab6ad6c34a3db1 git Not specified
CNA Linux Linux affected 3bf2bd20734e3e6ffda53719a9c10fb3ee9c5ffa dbcedbe4819ae21274ea77469e61e46a878b9943 git Not specified
CNA Linux Linux affected 3bf2bd20734e3e6ffda53719a9c10fb3ee9c5ffa 57debc907aef66319d244009d3370dcd97388d37 git Not specified
CNA Linux Linux affected 3bf2bd20734e3e6ffda53719a9c10fb3ee9c5ffa d761be1b8f2bbabc41252deb79a426d3f0d4fa10 git Not specified
CNA Linux Linux affected 3bf2bd20734e3e6ffda53719a9c10fb3ee9c5ffa cab9bf5f68f76cd44e0ec92bd4a60c9b83656a36 git Not specified
CNA Linux Linux affected 3bf2bd20734e3e6ffda53719a9c10fb3ee9c5ffa c9d293d6bb0575fcb1f3408129453187e2a28a4e git Not specified
CNA Linux Linux affected 4.14 Not specified
CNA Linux Linux unaffected 4.14 semver Not specified
CNA Linux Linux unaffected 6.1.188 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.157 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.110 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.52 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.6 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/d761be1b8f2bbabc41252deb79a426d3f0d4fa10 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/2679b11e9256bd70a5ef41783bab6ad6c34a3db1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/57debc907aef66319d244009d3370dcd97388d37 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/dbcedbe4819ae21274ea77469e61e46a878b9943 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/cab9bf5f68f76cd44e0ec92bd4a60c9b83656a36 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c9d293d6bb0575fcb1f3408129453187e2a28a4e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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