From: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com> stable inclusion from stable-v6.6.135 commit 546c18a14924eb521fe168d916d7ce28f1e13c1d category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/14409 CVE: CVE-2026-31667 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 4cda78d6f8bf2b700529f2fbccb994c3e826d7c2 upstream. 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) Fixes: ff462551235d ("Input: uinput - switch to the new FF interface") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/CABXGCsMoxag+kEwHhb7KqhuyxfmGGd0P=tHZyb1uKE0pLr8... Signed-off-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com> Link: https://patch.msgid.link/20260407075031.38351-1-mikhail.v.gavrilov@gmail.com Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Xia Fukun <xiafukun@huawei.com> --- drivers/input/misc/uinput.c | 28 +++++++++++++++++++++------- 1 file changed, 21 insertions(+), 7 deletions(-) diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c index edb62a284548..fd624c35a328 100644 --- a/drivers/input/misc/uinput.c +++ b/drivers/input/misc/uinput.c @@ -57,6 +57,7 @@ struct uinput_device { struct input_dev *dev; struct mutex mutex; enum uinput_state state; + spinlock_t state_lock; wait_queue_head_t waitq; unsigned char ready; unsigned char head; @@ -146,19 +147,15 @@ static void uinput_request_release_slot(struct uinput_device *udev, static int uinput_request_send(struct uinput_device *udev, struct uinput_request *request) { - int retval; + int retval = 0; - retval = mutex_lock_interruptible(&udev->mutex); - if (retval) - return retval; + spin_lock(&udev->state_lock); if (udev->state != UIST_CREATED) { retval = -ENODEV; goto out; } - init_completion(&request->done); - /* * Tell our userspace application about this new request * by queueing an input event. @@ -166,7 +163,7 @@ static int uinput_request_send(struct uinput_device *udev, uinput_dev_event(udev->dev, EV_UINPUT, request->code, request->id); out: - mutex_unlock(&udev->mutex); + spin_unlock(&udev->state_lock); return retval; } @@ -175,6 +172,13 @@ static int uinput_request_submit(struct uinput_device *udev, { int retval; + /* + * Initialize completion before allocating the request slot. + * Once the slot is allocated, uinput_flush_requests() may + * complete it at any time, so it must be initialized first. + */ + init_completion(&request->done); + retval = uinput_request_reserve_slot(udev, request); if (retval) return retval; @@ -289,7 +293,14 @@ static void uinput_destroy_device(struct uinput_device *udev) struct input_dev *dev = udev->dev; enum uinput_state old_state = udev->state; + /* + * Update state under state_lock so that concurrent + * uinput_request_send() sees the state change before we + * flush pending requests and tear down the device. + */ + spin_lock(&udev->state_lock); udev->state = UIST_NEW_DEVICE; + spin_unlock(&udev->state_lock); if (dev) { name = dev->name; @@ -366,7 +377,9 @@ static int uinput_create_device(struct uinput_device *udev) if (error) goto fail2; + spin_lock(&udev->state_lock); udev->state = UIST_CREATED; + spin_unlock(&udev->state_lock); return 0; @@ -384,6 +397,7 @@ static int uinput_open(struct inode *inode, struct file *file) return -ENOMEM; mutex_init(&newdev->mutex); + spin_lock_init(&newdev->state_lock); spin_lock_init(&newdev->requests_lock); init_waitqueue_head(&newdev->requests_waitq); init_waitqueue_head(&newdev->waitq); -- 2.34.1