{"id":"CVE-2026-31667","summary":"Input: uinput - fix circular locking dependency with ff-core","details":"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-\u003emutex -\u003e udev-\u003emutex -\u003e input_mutex -\u003e dev-\u003emutex -\u003e ff-\u003emutex\n\nThe cycle is caused by four lock acquisition paths:\n\n1. ff upload: input_ff_upload() holds ff-\u003emutex and calls\n   uinput_dev_upload_effect() -\u003e uinput_request_submit() -\u003e\n   uinput_request_send(), which acquires udev-\u003emutex.\n\n2. device create: uinput_ioctl_handler() holds udev-\u003emutex and calls\n   uinput_create_device() -\u003e input_register_device(), which acquires\n   input_mutex.\n\n3. device register: input_register_device() holds input_mutex and\n   calls kbd_connect() -\u003e input_register_handle(), which acquires\n   dev-\u003emutex.\n\n4. evdev release: evdev_release() calls input_flush_device() under\n   dev-\u003emutex, which calls input_ff_flush() acquiring ff-\u003emutex.\n\nFix this by introducing a new state_lock spinlock to protect\nudev-\u003estate and udev-\u003edev access in uinput_request_send() instead of\nacquiring udev-\u003emutex.  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-\u003emutex -\u003e udev-\u003emutex 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-\u003estate in uinput_create_device() and\nuinput_destroy_device() with the same state_lock spinlock.\n\nAdditionally, move init_completion(&request-\u003edone) 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-\u003emutex -\u003e state_lock (spinlock, leaf)\n  udev-\u003emutex -\u003e state_lock (spinlock, leaf)\n  udev-\u003emutex -\u003e input_mutex -\u003e dev-\u003emutex -\u003e ff-\u003emutex (no back-edge)","modified":"2026-05-18T05:59:53.262017346Z","published":"2026-04-24T14:45:15.937Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31667.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/1534661043c434b81cfde26b97a2fb2460329cf0"},{"type":"WEB","url":"https://git.kernel.org/stable/c/1e09dfbb4f5d20ee111f92325a00f85778a5f328"},{"type":"WEB","url":"https://git.kernel.org/stable/c/271ee71a1917b89f6d73ec82dd091c33d92ee617"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4cda78d6f8bf2b700529f2fbccb994c3e826d7c2"},{"type":"WEB","url":"https://git.kernel.org/stable/c/546c18a14924eb521fe168d916d7ce28f1e13c1d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/71a9729f412e2c692a35c542e14b706fb342927f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/974f7b138c3a96dd5cd53d1b33409cd7b2229dc6"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a3d6c9c053c9c605651508569230ead633b13f76"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31667.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31667"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"ff462551235d8d7d843a005950bc90924fcedede"},{"fixed":"71a9729f412e2c692a35c542e14b706fb342927f"},{"fixed":"271ee71a1917b89f6d73ec82dd091c33d92ee617"},{"fixed":"974f7b138c3a96dd5cd53d1b33409cd7b2229dc6"},{"fixed":"546c18a14924eb521fe168d916d7ce28f1e13c1d"},{"fixed":"a3d6c9c053c9c605651508569230ead633b13f76"},{"fixed":"1e09dfbb4f5d20ee111f92325a00f85778a5f328"},{"fixed":"1534661043c434b81cfde26b97a2fb2460329cf0"},{"fixed":"4cda78d6f8bf2b700529f2fbccb994c3e826d7c2"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-31667.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.6.19"},{"fixed":"5.10.253"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.203"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.169"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.135"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.82"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.23"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"6.19.13"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-31667.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}