---
id: "CVE-2026-98832"
kind: "vulnerability"
aliases: ["CVE-2026-98832"]
title: "Linux kernel: blk-cgroup lock wrongly re-enables interrupts, risking deadlock"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "other"
products: []
ecosystems: []
tags: ["device-mapper", "dm-thin", "linux-kernel", "other", "self-hosted"]
not_affected_if: ["no-blk-cgroup", "no-dm-thin"]
published_at: "2026-10-18T16:17:37+00:00"
first_seen_at: "2026-10-23T21:57:17+00:00"
updated_at: "2026-10-25T05:13:21+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98832", "first_seen_at": "2026-10-23T21:57:17+00:00"}]
---

# Linux kernel: blk-cgroup lock wrongly re-enables interrupts, risking deadlock

In the Linux kernel's block cgroup code, a lock helper unconditionally re-enables interrupts even when the caller already had them disabled, which can let a completion softirq re-acquire a held lock. The sources describe this as a deadlock in device-mapper thin provisioning (dm-thin) that lockdep flags, and the fix saves and restores the caller's interrupt state.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- unknown

## Fix

- Update to a Linux kernel release that includes the commit 'blk-cgroup: save IRQ state in blkg_tryget_closest()'; the sources do not list fixed versions.

## Timeline

- 2026-10-23T21:57:17+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98832

## From the sources

In the Linux kernel, the following vulnerability has been resolved:

blk-cgroup: save IRQ state in blkg_tryget_closest()

bio_set_dev() associates the bio with a blkg through bio_associate_blkg().
If the blkg lookup misses, blkg_tryget_closest() takes q->queue_lock with
spin_lock_irq() and releases it with spin_unlock_irq(), which
unconditionally enables local interrupts.

Callers may call bio_set_dev() with interrupts already disabled, e.g.
dm-thin's pool_map() does so while holding pool->lock taken with
spin_lock_irq().  The nested spin_unlock_irq() then enables interrupts
while pool->lock is still held, so an I/O completion softirq can run on
the same CPU, re-acquire pool->lock (thin_endio(), or overwrite_endio()
-> complete_mapping_preparation()) and deadlock.  lockdep reports this
as inconsistent SOFTIRQ-ON-W to IN-SOFTIRQ-W usage.

Commit 3a762de55b4e ("block: save irq state in blkg_lookup_create()")
fixed the same problem while the lock lived in blkg_lookup_create(), but
commit 9327a865e395 ("blk-cgroup: don't nest queue_lock under rcu in
blkg_lookup_create()") moved the locking into blkg_tryget_closest() and
reverted it to spin_lock_irq().

Save and restore the caller's IRQ state instead.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_