CVE-2026-31667 — linux / linux_kernel
Improper LockingIn 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:
-
ff upload: input_ff_upload() holds ff->mutex and calls uinput_dev_upload_effect() -> uinput_request_submit() -> uinput_request_send(), which acquires udev->mutex.
-
device create: uinput_ioctl_handler() holds udev->mutex and calls uinput_create_device() -> input_register_device(), which acquires input_mutex.
-
device register: input_register_device() holds input_mutex and calls kbd_connect() -> input_register_handle(), which acquires dev->mutex.
-
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)
| Software | From | Fixed in |
|---|---|---|
| linux / linux_kernel | 2.6.19.1 | 5.10.253 |
| linux / linux_kernel | 5.11 | 5.15.203 |
| linux / linux_kernel | 5.16 | 6.1.169 |
| linux / linux_kernel | 6.2 | 6.6.135 |
| linux / linux_kernel | 6.7 | 6.12.82 |
| linux / linux_kernel | 6.13 | 6.18.23 |
| linux / linux_kernel | 6.19 | 6.19.13 |
| linux / linux_kernel | 2.6.19 | 2.6.19.x |
| linux / linux_kernel | 7.0-rc1 | 7.0-rc1.x |
| linux / linux_kernel | 7.0-rc2 | 7.0-rc2.x |
| linux / linux_kernel | 7.0-rc3 | 7.0-rc3.x |
| linux / linux_kernel | 7.0-rc4 | 7.0-rc4.x |
| linux / linux_kernel | 7.0-rc5 | 7.0-rc5.x |
| linux / linux_kernel | 7.0-rc6 | 7.0-rc6.x |
| linux / linux_kernel | 7.0-rc7 | 7.0-rc7.x |
- https://git.kernel.org/stable/c/1534661043c434b81cfde26b97a2fb2460329cf0
- https://git.kernel.org/stable/c/1e09dfbb4f5d20ee111f92325a00f85778a5f328
- https://git.kernel.org/stable/c/271ee71a1917b89f6d73ec82dd091c33d92ee617
- https://git.kernel.org/stable/c/4cda78d6f8bf2b700529f2fbccb994c3e826d7c2
- https://git.kernel.org/stable/c/546c18a14924eb521fe168d916d7ce28f1e13c1d
- https://git.kernel.org/stable/c/71a9729f412e2c692a35c542e14b706fb342927f
- https://git.kernel.org/stable/c/974f7b138c3a96dd5cd53d1b33409cd7b2229dc6
- https://git.kernel.org/stable/c/a3d6c9c053c9c605651508569230ead633b13f76
Deep Security Visibility Without the Complexity
SynScan provides clear, real-time security insights so you can monitor your attack surface, spot risks early, and act fast—without extra complexity.
- No setup fees
- 5-min deployment
- Cancel anytime
Frequently Asked Questions
A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.
CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.
A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.
Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.
Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.
SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.