{"cve":"CVE-2026-31667","nvd":{"published":"2026-04-24T15:16:46.390","modified":"2026-10-19T19:18:04.560","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nInput: uinput - fix circular locking dependency with ff-core\n\nA lockdep circular locking dependency warning can be triggered\nreproducibly when using a force-feedback gamepad with uinput (for\nexample, playing ELDEN RING under Wine with a Flydigi Vader 5\ncontroller):\n\n  ff->mutex -> udev->mutex -> input_mutex -> dev->mutex -> ff->mutex\n\nThe cycle is caused by four lock acquisition paths:\n\n1. ff upload: input_ff_upload() holds ff->mutex and calls\n   uinput_dev_upload_effect() -> uinput_request_submit() ->\n   uinput_request_send(), which acquires udev->mutex.\n\n2. device create: uinput_ioctl_handler() holds udev->mutex and calls\n   uinput_create_device() -> input_register_device(), which acquires\n   input_mutex.\n\n3. device register: input_register_device() holds input_mutex and\n   calls kbd_connect() -> input_register_handle(), which acquires\n   dev->mutex.\n\n4. evdev release: evdev_release() calls input_flush_device() under\n   dev->mutex, which calls input_ff_flush() acquiring ff->mutex.\n\nFix this by introducing a new state_lock spinlock to protect\nudev->state and udev->dev access in uinput_request_send() instead of\nacquiring udev->mutex.  The function only needs to atomically check\ndevice state and queue an input event into the ring buffer via\nuinput_dev_event() -- both operations are safe under a spinlock\n(ktime_get_ts64() and wake_up_interruptible() do not sleep).  This\nbreaks the ff->mutex -> udev->mutex link since a spinlock is a leaf in\nthe lock ordering and cannot form cycles with mutexes.\n\nTo keep state transitions visible to uinput_request_send(), protect\nwrites to udev->state in uinput_create_device() and\nuinput_destroy_device() with the same state_lock spinlock.\n\nAdditionally, move init_completion(&request->done) from\nuinput_request_send() to uinput_request_submit() before\nuinput_request_reserve_slot().  Once the slot is allocated,\nuinput_flush_requests() may call complete() on it at any time from\nthe destroy path, so the completion must be initialised before the\nrequest becomes visible.\n\nLock ordering after the fix:\n\n  ff->mutex -> state_lock (spinlock, leaf)\n  udev->mutex -> state_lock (spinlock, leaf)\n  udev->mutex -> input_mutex -> dev->mutex -> ff->mutex (no back-edge)","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8},"cwes":["CWE-667","CWE-362"],"references":["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"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-21T03:43:09.190223697+00:00"},"epss":{"cve":"CVE-2026-31667","score":0.00096,"percentile":0.00696,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}