null_blk: reject per-device queue resize for shared tag set (CVE-2026-90186) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-90186

null_blk: reject per-device queue resize for shared tag set

Answer in brief

CVE-2026-90186 records a Unknown severity vulnerability in null_blk: reject per-device queue resize for shared tag set. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 17, 2026Updated Sep 17, 2026Source checked Sep 17, 2026First seen by HOL Sep 17, 2026Material review Sep 17, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=45919fbfe1c487c17ea1d198534339a5e8abeae3 <9c7bae099ddc92676ad1b7e29dd6c089e5f6196c \|\| >=45919fbfe1c487c17ea1d198534339a5e8abeae3 <fcd53f3e8b758c79c3f2420d28a2a1dce6fda61a \|\| >=45919fbfe1c487c17ea1d198534339a5e8abeae3 <f609f7bf9ce8c2fc427705c4a9f623a281239d06 \|\| >=45919fbfe1c487c17ea1d198534339a5e8abeae3 <3e35ad503386a2e8a0e0460530dcbf421c79f6f2 \|\| >=45919fbfe1c487c17ea1d198534339a5e8abeae3 <baff300541a0012907cdde349728739fe16176d7 \|\| >=45919fbfe1c487c17ea1d198534339a5e8abeae3 <1cdfe2fa62b48728a9b436fbbd3dbe4c11593e24	9c7bae099ddc92676ad1b7e29dd6c089e5f6196c, fcd53f3e8b758c79c3f2420d28a2a1dce6fda61a, f609f7bf9ce8c2fc427705c4a9f623a281239d06, 3e35ad503386a2e8a0e0460530dcbf421c79f6f2, baff300541a0012907cdde349728739fe16176d7, 1cdfe2fa62b48728a9b436fbbd3dbe4c11593e24
Linux/Linuxgeneric	5.5	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to 9c7bae099ddc92676ad1b7e29dd6c089e5f6196c if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 17, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 17, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 17, 2026

Sources and claim methodology

Upstream source description

In the Linux kernel, the following vulnerability has been resolved: null_blk: reject per-device queue resize for shared tag set When shared_tags is enabled, null_setup_tagset() makes the device use the global tag_set, whose driver_data stays NULL. null_map_queues() therefore falls back to the module-wide g_submit_queues/g_poll_queues instead of any per-device value. Resizing submit_queues or poll_queues via configfs on such a device calls blk_mq_update_nr_hw_queues() on the shared set, shrinking set->nr_hw_queues. __blk_mq_realloc_hw_ctxs() only grows the q->queue_hw_ctx[] allocation, so on shrink it merely exits and NULLs the now-excess hctx slots. null_map_queues(), however, keeps mapping CPUs with the unchanged g_submit_queues/g_poll_queues, so mq_map[] ends up pointing at those NULLed hctx slots. blk_mq_map_swqueue() then dereferences the NULL hctx (hctx->cpumask), crashing the kernel: [ 460.218374] KASAN: null-ptr-deref in range [0x0000000000000098-0x000000000000009f] [ 460.219003] CPU: 24 UID: 0 PID: 1492 Comm: sh Not tainted 7.2.0-rc2+ #67 PREEMPT(full) [ 460.219792] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014 [ 460.220452] RIP: 0010:blk_mq_map_swqueue+0x4db/0x1430 ...... [ 460.228977] Call Trace: [ 460.229175] <TASK> [ 460.229354] blk_mq_update_nr_hw_queues+0xd49/0x11c0 [ 460.229779] ? __pfx_blk_mq_update_nr_hw_queues+0x10/0x10 [ 460.230200] nullb_update_nr_hw_queues+0x1a9/0x370 [null_blk] [ 460.230694] nullb_device_submit_queues_store+0xd9/0x170 [null_blk] [ 460.231190] ? __pfx_nullb_device_submit_queues_store+0x10/0x10 [null_blk] [ 460.231776] ? configfs_write_iter+0x35c/0x4e0 [ 460.232122] configfs_write_iter+0x286/0x4e0 [ 460.232460] vfs_write+0x52d/0xd00 [ 460.232779] ? __x64_sys_openat+0x108/0x1d0 [ 460.233106] ? __pfx_vfs_write+0x10/0x10 [ 460.233413] ? fdget_pos+0x1cf/0x4c0 [ 460.233745] ? fput_close+0x133/0x190 [ 460.234038] ? __pfx_expand_files+0x10/0x10 [ 460.234368] ksys_write+0xfc/0x1d0 Reproducer: modprobe null_blk shared_tags=1 submit_queues=64 poll_queues=1 mkdir /sys/kernel/config/nullb/dev echo 1 > /sys/kernel/config/nullb/dev/power echo 1 > /sys/kernel/config/nullb/dev/submit_queues A per-device resize of a shared tag set is meaningless anyway, so reject it with -EINVAL in nullb_update_nr_hw_queues() when the device is bound to the global tag_set.

Quoted source text, attributed separately from HOL analysis.