{"id":"AZL-83651","summary":"CVE-2026-31667 affecting package kernel for versions less than 6.6.137.1-1","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":"2026-08-28T17:47:51.971761376Z","published":"2026-04-24T15:16:46Z","upstream":["CVE-2026-31667"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31667"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.6.137.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-83651.json"}}],"schema_version":"1.9.0"}