Input: uinput - fix circular locking dependency with ff-core

Summary

In 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: 1. ff upload: input_ff_upload() holds ff->mutex and calls uinput_dev_upload_effect() -> uinput_request_submit() -> uinput_request_send(), which acquires udev->mutex. 2. device create: uinput_ioctl_handler() holds udev->mutex and calls uinput_create_device() -> input_register_device(), which acquires input_mutex. 3. device register: input_register_device() holds input_mutex and calls kbd_connect() -> input_register_handle(), which acquires dev->mutex. 4. 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)

Timeline

1. Apr 24, 2026, 2:45 PM UTCCVE published
2. Oct 16, 2026, 3:11 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Oct 19, 2026, 6:56 PM UTCRecord last updated

Affected versions

• Linux Linux

  From ff462551235d8d7d843a005950bc90924fcedede · fixed in 71a9729f412e2c692a35c542e14b706fb342927f; From ff462551235d8d7d843a005950bc90924fcedede · fixed in 271ee71a1917b89f6d73ec82dd091c33d92ee617; From ff462551235d8d7d843a005950bc90924fcedede · fixed in 974f7b138c3a96dd5cd53d1b33409cd7b2229dc6; From ff462551235d8d7d843a005950bc90924fcedede · fixed in 546c18a14924eb521fe168d916d7ce28f1e13c1d; From ff462551235d8d7d843a005950bc90924fcedede · fixed in a3d6c9c053c9c605651508569230ead633b13f76; From ff462551235d8d7d843a005950bc90924fcedede · fixed in 1e09dfbb4f5d20ee111f92325a00f85778a5f328; From ff462551235d8d7d843a005950bc90924fcedede · fixed in 1534661043c434b81cfde26b97a2fb2460329cf0; From ff462551235d8d7d843a005950bc90924fcedede · fixed in 4cda78d6f8bf2b700529f2fbccb994c3e826d7c2

• Linux Linux

  2.6.19

• KernelLinux

  From 2.6.19 · fixed in 5.10.253; From 5.11.0 · fixed in 5.15.203; From 5.16.0 · fixed in 6.1.169; From 6.2.0 · fixed in 6.6.135; From 6.7.0 · fixed in 6.12.82; From 6.13.0 · fixed in 6.18.23; From 6.19.0 · fixed in 6.19.13

References 8