{"id":"CVE-2026-90189","summary":"null_blk: register configfs subsystem after creating default devices","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnull_blk: register configfs subsystem after creating default devices\n\nIn null_init(), configfs_register_subsystem() currently runs before\nregister_blkdev(), so when null_blk is built as a module, a racing mkdir()\n+ poweron from userspace can reach null_add_dev() while null_major is still\n0. __add_disk() then hits WARN_ON(disk-\u003eminors) (major=0 with minors!=0)\nand fails:\n\n[root@fedora ~]# [ 2366.521436] WARNING: block/genhd.c:476 at __add_disk+0x8a7/0xde0,\n[ 2366.523552] Modules linked in: null_blk(+) nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib\n[ 2366.529081] CPU: 26 UID: 0 PID: 1600 Comm: sh Not tainted 7.2.0-rc1+ #66 PREEMPT(full)\n......\n[ 2366.547251] Call Trace:\n[ 2366.547575]  \u003cTASK\u003e\n[ 2366.547831]  ? _raw_spin_lock+0x84/0xe0\n[ 2366.548260]  add_disk_fwnode+0x114/0x560\n[ 2366.548739]  null_add_dev+0x102d/0x1b80 [null_blk]\n[ 2366.549310]  ? __pfx_null_add_dev+0x10/0x10 [null_blk]\n[ 2366.549906]  ? mutex_lock+0xde/0x1c0\n[ 2366.550361]  ? __pfx_mutex_lock+0x10/0x10\n[ 2366.550827]  nullb_device_power_store+0x1e7/0x280 [null_blk]\n[ 2366.551499]  ? __pfx_nullb_device_power_store+0x10/0x10 [null_blk]\n[ 2366.552177]  ? __kmalloc_cache_noprof+0x1f5/0x470\n[ 2366.552748]  ? configfs_write_iter+0x35c/0x4e0\n[ 2366.553242]  configfs_write_iter+0x286/0x4e0\n[ 2366.553787]  vfs_write+0x52d/0xd00\n[ 2366.554169]  ? __pfx_vfs_write+0x10/0x10\n[ 2366.554679]  ? __pfx___css_rstat_updated+0x10/0x10\n[ 2366.555196]  ? fdget_pos+0x1cf/0x4c0\n[ 2366.555649]  ksys_write+0xfc/0x1d0\n......\n\nAdditionally, the err_dev path destroys all devices on nullb_list while\nconfigfs is still registered. If a racing mkdir() + poweron puts a user\ndevice on the list, null_destroy_dev()-\u003enull_free_dev() kfrees the user\ndevice's nullb_device but /sys/kernel/config/nullb/\u003cname\u003e is still\nreachable. Any userspace access to the item will trigger a UAF.\n\nFor simplicity, move configfs_register_subsystem() to the end to solve\nthe problems above.","modified":"2026-09-18T03:48:36.347344239Z","published":"2026-09-17T16:07:10.992Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90189.json"},"references":[{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"},{"type":"WEB","url":"https://git.kernel.org/stable/c/2679b11e9256bd70a5ef41783bab6ad6c34a3db1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/57debc907aef66319d244009d3370dcd97388d37"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c9d293d6bb0575fcb1f3408129453187e2a28a4e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/cab9bf5f68f76cd44e0ec92bd4a60c9b83656a36"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d761be1b8f2bbabc41252deb79a426d3f0d4fa10"},{"type":"WEB","url":"https://git.kernel.org/stable/c/dbcedbe4819ae21274ea77469e61e46a878b9943"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90189.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-90189"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"3bf2bd20734e3e6ffda53719a9c10fb3ee9c5ffa"},{"fixed":"2679b11e9256bd70a5ef41783bab6ad6c34a3db1"},{"fixed":"dbcedbe4819ae21274ea77469e61e46a878b9943"},{"fixed":"57debc907aef66319d244009d3370dcd97388d37"},{"fixed":"d761be1b8f2bbabc41252deb79a426d3f0d4fa10"},{"fixed":"cab9bf5f68f76cd44e0ec92bd4a60c9b83656a36"},{"fixed":"c9d293d6bb0575fcb1f3408129453187e2a28a4e"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90189.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.14.0"},{"fixed":"6.1.188"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.157"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.110"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.52"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.6"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90189.json"}}],"schema_version":"1.9.0"}