{"id":"CVE-2026-31667","title":"Input: uinput - fix circular locking dependency with ff-core","summary":"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 ga…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= ff462551235d8d7d843a005950bc90924fcedede < 71a9729f412e2c692a35c542e14b706fb342927f","Linux >= ff462551235d8d7d843a005950bc90924fcedede < 271ee71a1917b89f6d73ec82dd091c33d92ee617","Linux >= ff462551235d8d7d843a005950bc90924fcedede < 974f7b138c3a96dd5cd53d1b33409cd7b2229dc6","Linux >= ff462551235d8d7d843a005950bc90924fcedede < 546c18a14924eb521fe168d916d7ce28f1e13c1d","Linux >= ff462551235d8d7d843a005950bc90924fcedede < a3d6c9c053c9c605651508569230ead633b13f76","Linux >= ff462551235d8d7d843a005950bc90924fcedede < 1e09dfbb4f5d20ee111f92325a00f85778a5f328","Linux >= ff462551235d8d7d843a005950bc90924fcedede < 1534661043c434b81cfde26b97a2fb2460329cf0","Linux >= ff462551235d8d7d843a005950bc90924fcedede < 4cda78d6f8bf2b700529f2fbccb994c3e826d7c2","Linux 2.6.19"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-16T15:11:55.311439Z"},"published":"2026-04-24","updated":"2026-10-16","sourceUpdated":"2026-10-16T15:20:22.366Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-31667","references":[{"url":"https://git.kernel.org/stable/c/71a9729f412e2c692a35c542e14b706fb342927f"},{"url":"https://git.kernel.org/stable/c/271ee71a1917b89f6d73ec82dd091c33d92ee617"},{"url":"https://git.kernel.org/stable/c/974f7b138c3a96dd5cd53d1b33409cd7b2229dc6"},{"url":"https://git.kernel.org/stable/c/546c18a14924eb521fe168d916d7ce28f1e13c1d"},{"url":"https://git.kernel.org/stable/c/a3d6c9c053c9c605651508569230ead633b13f76"},{"url":"https://git.kernel.org/stable/c/1e09dfbb4f5d20ee111f92325a00f85778a5f328"},{"url":"https://git.kernel.org/stable/c/1534661043c434b81cfde26b97a2fb2460329cf0"},{"url":"https://git.kernel.org/stable/c/4cda78d6f8bf2b700529f2fbccb994c3e826d7c2"}],"tags":["cve.org"],"epss":0.00136,"epssPercentile":0.0269,"ingestedAt":"2026-10-16T17:24:46.669Z","slug":"CVE-2026-31667","body":"## Overview\n\nIn 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)\n\n## Affected\n\n- `Linux >= ff462551235d8d7d843a005950bc90924fcedede < 71a9729f412e2c692a35c542e14b706fb342927f`\n- `Linux >= ff462551235d8d7d843a005950bc90924fcedede < 271ee71a1917b89f6d73ec82dd091c33d92ee617`\n- `Linux >= ff462551235d8d7d843a005950bc90924fcedede < 974f7b138c3a96dd5cd53d1b33409cd7b2229dc6`\n- `Linux >= ff462551235d8d7d843a005950bc90924fcedede < 546c18a14924eb521fe168d916d7ce28f1e13c1d`\n- `Linux >= ff462551235d8d7d843a005950bc90924fcedede < a3d6c9c053c9c605651508569230ead633b13f76`\n- `Linux >= ff462551235d8d7d843a005950bc90924fcedede < 1e09dfbb4f5d20ee111f92325a00f85778a5f328`\n- `Linux >= ff462551235d8d7d843a005950bc90924fcedede < 1534661043c434b81cfde26b97a2fb2460329cf0`\n- `Linux >= ff462551235d8d7d843a005950bc90924fcedede < 4cda78d6f8bf2b700529f2fbccb994c3e826d7c2`\n- `Linux 2.6.19`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}