# CVE-2026-64164: btrfs: tracepoints: fix sleep while in atomic context in btrfs_sync_file()

> A kernel bug in btrfs tracepoints causes a sleep in atomic context, leading to a system crash when specific tracing is enabled.

- **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:** 19 Jul 2026
- **Updated:** 19 Jul 2026
- **Also known as:** BELL-CVE-2026-64164, DEBIAN-CVE-2026-64164, GHSA-w7p5-2w2w-6hjm, UBUNTU-CVE-2026-64164

## What is CVE-2026-64164?

CVE-2026-64164 is a medium-severity vulnerability in Linux kernel, published on 19 Jul 2026. 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:

btrfs: tracepoints: fix sleep while in atomic context in btrfs_sync_file()

The trace event btrfs_sync_file() is called in an atomic context (all trace
events are) and its call to dput(), which is needed due to the call to
dget_parent(), can sleep, triggering a kernel splat.

This can be reproduced by enabling the trace event and running btrfs/056
from fstests for example. The splat shown in dmesg is the following:

  [53.919] BUG: sleeping function called from invalid context at fs/dcache.c:970
  [53.947] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 32773, name: xfs_io
  [53.988] preempt_count: 2, expected: 0
  [53.967] RCU nest depth: 0, expected: 0
  [53.943] Preemption disabled at:
  [53.944] [<0000000000000000>] 0x0
  [54.078] CPU: 0 UID: 0 PID: 32773 Comm: xfs_io Tainted: G        W           7.1.0-rc1-btrfs-next-232+ #1 PREEMPT(full)
  [54.070] Tainted: [W]=WARN
  [54.071] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014
  [54.072] Call Trace:
  [54.074]  <TASK>
  [54.076]  dump_stack_lvl+0x56/0x80
  [54.079]  __might_resched.cold+0xd6/0x10f
  [54.072]  dput.part.0+0x24/0x110
  [54.078]  trace_event_raw_event_btrfs_sync_file+0x75/0x140 [btrfs]
  [54.089]  btrfs_sync_file+0x1ed/0x530 [btrfs]
  [54.087]  ? __handle_mm_fault+0x8ae/0xed0
  [54.089]  btrfs_do_write_iter+0x172/0x210 [btrfs]
  [54.091]  vfs_write+0x21f/0x450
  [54.094]  __x64_sys_pwrite64+0x8d/0xc0
  [54.096]  ? do_user_addr_fault+0x20c/0x670
  [54.099]  do_syscall_64+0x60/0xf20
  [54.092]  ? clear_bhb_loop+0x60/0xb0
  [54.094]  entry_SYSCALL_64_after_hwframe+0x76/0x7e

So stop using dget_parent() and dput() and access the parent dentry
directly as dentry->d_parent. This is also what ext4 is doing in
its equivalent trace event ext4_sync_file_enter().

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-64164?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-64164?

Apply the vendor's patch.

## Is CVE-2026-64164 being exploited?

There is no known exploitation of CVE-2026-64164 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-2026-64164 and fix it if it is affected.

What it is: CVE-2026-64164 is a medium-severity vulnerability in Linux kernel, published on 19 Jul 2026. 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-2026-64164 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-2026-64164/ (Markdown: https://insights.sbomify.com/CVE-2026-64164/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64164
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64164
- OSV: https://osv.dev/vulnerability/CVE-2026-64164

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64164/
Summaries are generated and may contain mistakes; the official description above is the record.