{"id":"AZL-102141","summary":"CVE-2026-90189 affecting package kernel 6.6.150.1-1","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":"2026-09-18T14:17:49.338832445Z","published":"2026-09-17T17:17:13Z","upstream":["CVE-2026-90189"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-90189"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"6.6.150.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-102141.json"}}],"schema_version":"1.9.0"}