{"id":"CVE-2026-90186","summary":"null_blk: reject per-device queue resize for shared tag set","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnull_blk: reject per-device queue resize for shared tag set\n\nWhen shared_tags is enabled, null_setup_tagset() makes the device use the\nglobal tag_set, whose driver_data stays NULL. null_map_queues() therefore\nfalls back to the module-wide g_submit_queues/g_poll_queues instead of any\nper-device value.\n\nResizing submit_queues or poll_queues via configfs on such a device calls\nblk_mq_update_nr_hw_queues() on the shared set, shrinking\nset-\u003enr_hw_queues.  __blk_mq_realloc_hw_ctxs() only grows the\nq-\u003equeue_hw_ctx[] allocation, so on shrink it merely exits and NULLs the\nnow-excess hctx slots. null_map_queues(), however, keeps mapping CPUs with\nthe unchanged g_submit_queues/g_poll_queues, so mq_map[] ends up pointing\nat those NULLed hctx slots. blk_mq_map_swqueue() then dereferences the NULL\nhctx (hctx-\u003ecpumask), crashing the kernel:\n\n[  460.218374] KASAN: null-ptr-deref in range [0x0000000000000098-0x000000000000009f]\n[  460.219003] CPU: 24 UID: 0 PID: 1492 Comm: sh Not tainted 7.2.0-rc2+ #67 PREEMPT(full)\n[  460.219792] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014\n[  460.220452] RIP: 0010:blk_mq_map_swqueue+0x4db/0x1430\n......\n[  460.228977] Call Trace:\n[  460.229175]  \u003cTASK\u003e\n[  460.229354]  blk_mq_update_nr_hw_queues+0xd49/0x11c0\n[  460.229779]  ? __pfx_blk_mq_update_nr_hw_queues+0x10/0x10\n[  460.230200]  nullb_update_nr_hw_queues+0x1a9/0x370 [null_blk]\n[  460.230694]  nullb_device_submit_queues_store+0xd9/0x170 [null_blk]\n[  460.231190]  ? __pfx_nullb_device_submit_queues_store+0x10/0x10 [null_blk]\n[  460.231776]  ? configfs_write_iter+0x35c/0x4e0\n[  460.232122]  configfs_write_iter+0x286/0x4e0\n[  460.232460]  vfs_write+0x52d/0xd00\n[  460.232779]  ? __x64_sys_openat+0x108/0x1d0\n[  460.233106]  ? __pfx_vfs_write+0x10/0x10\n[  460.233413]  ? fdget_pos+0x1cf/0x4c0\n[  460.233745]  ? fput_close+0x133/0x190\n[  460.234038]  ? __pfx_expand_files+0x10/0x10\n[  460.234368]  ksys_write+0xfc/0x1d0\n\nReproducer:\nmodprobe null_blk shared_tags=1 submit_queues=64 poll_queues=1\nmkdir /sys/kernel/config/nullb/dev\necho 1 \u003e /sys/kernel/config/nullb/dev/power\necho 1 \u003e /sys/kernel/config/nullb/dev/submit_queues\n\nA per-device resize of a shared tag set is meaningless anyway, so reject it\nwith -EINVAL in nullb_update_nr_hw_queues() when the device is bound to the\nglobal tag_set.","modified":"2026-09-18T03:48:36.348971729Z","published":"2026-09-17T16:07:09.047Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90186.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/1cdfe2fa62b48728a9b436fbbd3dbe4c11593e24"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3e35ad503386a2e8a0e0460530dcbf421c79f6f2"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9c7bae099ddc92676ad1b7e29dd6c089e5f6196c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/baff300541a0012907cdde349728739fe16176d7"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f609f7bf9ce8c2fc427705c4a9f623a281239d06"},{"type":"WEB","url":"https://git.kernel.org/stable/c/fcd53f3e8b758c79c3f2420d28a2a1dce6fda61a"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90186.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-90186"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"45919fbfe1c487c17ea1d198534339a5e8abeae3"},{"fixed":"9c7bae099ddc92676ad1b7e29dd6c089e5f6196c"},{"fixed":"fcd53f3e8b758c79c3f2420d28a2a1dce6fda61a"},{"fixed":"f609f7bf9ce8c2fc427705c4a9f623a281239d06"},{"fixed":"3e35ad503386a2e8a0e0460530dcbf421c79f6f2"},{"fixed":"baff300541a0012907cdde349728739fe16176d7"},{"fixed":"1cdfe2fa62b48728a9b436fbbd3dbe4c11593e24"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90186.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.5.0"},{"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-2026-90186.json"}}],"schema_version":"1.9.0"}