# CVE-2025-40317: regmap: slimbus: fix bus_context pointer in regmap init calls

> A null pointer dereference in the Linux kernel's regmap slimbus driver can cause a system crash during audio playback.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 8 Dec 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-40317, DEBIAN-CVE-2025-40317, GHSA-8c3q-mr36-wh76, ROOT-OS-DEBIAN-12-CVE-2025-40317, ROOT-OS-DEBIAN-13-CVE-2025-40317, ROOT-OS-UBUNTU-2204-CVE-2025-40317, ROOT-OS-UBUNTU-2404-CVE-2025-40317, UBUNTU-CVE-2025-40317

## What is CVE-2025-40317?

CVE-2025-40317 is a high-severity vulnerability in Linux, published on 8 Dec 2025. 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:

regmap: slimbus: fix bus_context pointer in regmap init calls

Commit 4e65bda8273c ("ASoC: wcd934x: fix error handling in
wcd934x_codec_parse_data()") revealed the problem in the slimbus regmap.
That commit breaks audio playback, for instance, on sdm845 Thundercomm
Dragonboard 845c board:

 Unable to handle kernel paging request at virtual address ffff8000847cbad4
 ...
 CPU: 5 UID: 0 PID: 776 Comm: aplay Not tainted 6.18.0-rc1-00028-g7ea30958b305 #11 PREEMPT
 Hardware name: Thundercomm Dragonboard 845c (DT)
 ...
 Call trace:
  slim_xfer_msg+0x24/0x1ac [slimbus] (P)
  slim_read+0x48/0x74 [slimbus]
  regmap_slimbus_read+0x18/0x24 [regmap_slimbus]
  _regmap_raw_read+0xe8/0x174
  _regmap_bus_read+0x44/0x80
  _regmap_read+0x60/0xd8
  _regmap_update_bits+0xf4/0x140
  _regmap_select_page+0xa8/0x124
  _regmap_raw_write_impl+0x3b8/0x65c
  _regmap_bus_raw_write+0x60/0x80
  _regmap_write+0x58/0xc0
  regmap_write+0x4c/0x80
  wcd934x_hw_params+0x494/0x8b8 [snd_soc_wcd934x]
  snd_soc_dai_hw_params+0x3c/0x7c [snd_soc_core]
  __soc_pcm_hw_params+0x22c/0x634 [snd_soc_core]
  dpcm_be_dai_hw_params+0x1d4/0x38c [snd_soc_core]
  dpcm_fe_dai_hw_params+0x9c/0x17c [snd_soc_core]
  snd_pcm_hw_params+0x124/0x464 [snd_pcm]
  snd_pcm_common_ioctl+0x110c/0x1820 [snd_pcm]
  snd_pcm_ioctl+0x34/0x4c [snd_pcm]
  __arm64_sys_ioctl+0xac/0x104
  invoke_syscall+0x48/0x104
  el0_svc_common.constprop.0+0x40/0xe0
  do_el0_svc+0x1c/0x28
  el0_svc+0x34/0xec
  el0t_64_sync_handler+0xa0/0xf0
  el0t_64_sync+0x198/0x19c

The __devm_regmap_init_slimbus() started to be used instead of
__regmap_init_slimbus() after the commit mentioned above and turns out
the incorrect bus_context pointer (3rd argument) was used in
__devm_regmap_init_slimbus(). It should be just "slimbus" (which is equal
to &slimbus->dev). Correct it. The wcd934x codec seems to be the only or
the first user of devm_regmap_init_slimbus() but we should fix it till
the point where __devm_regmap_init_slimbus() was introduced therefore
two "Fixes" tags.

While at this, also correct the same argument in __regmap_init_slimbus().

## Which versions are affected by CVE-2025-40317?


## How do I fix CVE-2025-40317?

Apply the vendor's patch.

## Is CVE-2025-40317 being exploited?

There is no known exploitation of CVE-2025-40317 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40317 and fix it if it is affected.

What it is: CVE-2025-40317 is a high-severity vulnerability in Linux, published on 8 Dec 2025. 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-2025-40317 in the wild and no public exploit code.

Affected product: Linux. 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-2025-40317/ (Markdown: https://insights.sbomify.com/CVE-2025-40317/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40317
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40317
- OSV: https://osv.dev/vulnerability/CVE-2025-40317

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40317/
Summaries are generated and may contain mistakes; the official description above is the record.