# CVE-2024-36478: null_blk: fix null-ptr-dereference while configuring 'power' and 'submit_queues'

> Concurrent configuration of null_blk power and submit_queues causes a kernel null pointer dereference, leading to a system crash.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Jun 2024
- **Updated:** 11 May 2026
- **Also known as:** AZL-48948, AZL-48962, BELL-CVE-2024-36478, DEBIAN-CVE-2024-36478, GHSA-66hj-w2gx-rg6c, ROOT-OS-DEBIAN-11-CVE-2024-36478, ROOT-OS-UBUNTU-2204-CVE-2024-36478, UBUNTU-CVE-2024-36478

## What is CVE-2024-36478?

CVE-2024-36478 is a medium-severity vulnerability in Linux kernel, published on 21 Jun 2024. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

null_blk: fix null-ptr-dereference while configuring 'power' and 'submit_queues'

Writing 'power' and 'submit_queues' concurrently will trigger kernel
panic:

Test script:

modprobe null_blk nr_devices=0
mkdir -p /sys/kernel/config/nullb/nullb0
while true; do echo 1 > submit_queues; echo 4 > submit_queues; done &
while true; do echo 1 > power; echo 0 > power; done

Test result:

BUG: kernel NULL pointer dereference, address: 0000000000000148
Oops: 0000 [#1] PREEMPT SMP
RIP: 0010:__lock_acquire+0x41d/0x28f0
Call Trace:
 <TASK>
 lock_acquire+0x121/0x450
 down_write+0x5f/0x1d0
 simple_recursive_removal+0x12f/0x5c0
 blk_mq_debugfs_unregister_hctxs+0x7c/0x100
 blk_mq_update_nr_hw_queues+0x4a3/0x720
 nullb_update_nr_hw_queues+0x71/0xf0 [null_blk]
 nullb_device_submit_queues_store+0x79/0xf0 [null_blk]
 configfs_write_iter+0x119/0x1e0
 vfs_write+0x326/0x730
 ksys_write+0x74/0x150

This is because del_gendisk() can concurrent with
blk_mq_update_nr_hw_queues():

nullb_device_power_store	nullb_apply_submit_queues
 null_del_dev
 del_gendisk
				 nullb_update_nr_hw_queues
				  if (!dev->nullb)
				  // still set while gendisk is deleted
				   return 0
				  blk_mq_update_nr_hw_queues
 dev->nullb = NULL

Fix this problem by resuing the global mutex to protect
nullb_device_power_store() and nullb_update_nr_hw_queues() from configfs.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2024-36478?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-36478?

Apply the vendor's patch.

## Is CVE-2024-36478 being exploited?

There is no known exploitation of CVE-2024-36478 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-36478 and fix it if it is affected.

What it is: CVE-2024-36478 is a medium-severity vulnerability in Linux kernel, published on 21 Jun 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2024-36478 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2024-36478/ (Markdown: https://insights.sbomify.com/CVE-2024-36478/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-36478
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-36478
- OSV: https://osv.dev/vulnerability/CVE-2024-36478

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-36478/
Summaries are generated and may contain mistakes; the official description above is the record.