From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7D0842EBB8C; Mon, 13 Apr 2026 16:16:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776096985; cv=none; b=ho9E1V6rtOKVOX9XgXYVmS98rU0quu+taoCstH2mS7pzh/PgutFPEDIiXBUIR+fVqlV/zKa++nU7wqA2qzTY4WVc2qVIeEyvXr6t5QOiW5ub/anvN8IaOPBI4jBtdGFkTxoW1jiC/1ALxVzMEc+dAbCqoH+rAUFzyf5KetSIJ7k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776096985; c=relaxed/simple; bh=BHHdONAJRa4ftbg1+Yqlfg8dqYjDy6J3A4P9BQ+7D+g=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=EAxPpbwQxQzwa7AwB3aUeshJVaQMzIxxK6mo5qI0BchlaF7F+Z8Rx7MENc2MnCFf67/7a6wama7XUqeH9j6NDutsSVVjEeJv8si/36BZTRj1SWTzIaIPfqtWuZWt8DHETpg6vTKkxWjOpZqrnMrcU+8PVsTIL798l9o2v0wykLM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=2ZiD0B2E; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="2ZiD0B2E" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 13DCFC2BCB8; Mon, 13 Apr 2026 16:16:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1776096985; bh=BHHdONAJRa4ftbg1+Yqlfg8dqYjDy6J3A4P9BQ+7D+g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=2ZiD0B2E/jxdkOQbOgpeKtydW88JDBpgr9gzePU7/lpuySWx2RzJoD0+EAGmckM2o M7N3uOQ1vXfnJzROVKomE2iGnoQQoZqabNjUE+Tx6QxACYOvhtvAMJDFehGLe3y6p7 syzgUjsQpIGM20UzZ+UXhUOrkWlId52uxLCkxMMQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Mikhail Gavrilov , Dmitry Torokhov Subject: [PATCH 6.1 05/55] Input: uinput - fix circular locking dependency with ff-core Date: Mon, 13 Apr 2026 18:00:39 +0200 Message-ID: <20260413155725.027691280@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260413155724.820472494@linuxfoundation.org> References: <20260413155724.820472494@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mikhail Gavrilov 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=tHZyb1uKE0pLr8Hkg@mail.gmail.com/ Signed-off-by: Mikhail Gavrilov Link: https://patch.msgid.link/20260407075031.38351-1-mikhail.v.gavrilov@gmail.com Signed-off-by: Dmitry Torokhov Signed-off-by: Greg Kroah-Hartman --- drivers/input/misc/uinput.c | 28 +++++++++++++++++++++------- 1 file changed, 21 insertions(+), 7 deletions(-) --- a/drivers/input/misc/uinput.c +++ b/drivers/input/misc/uinput.c @@ -56,6 +56,7 @@ 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; @@ -145,19 +146,15 @@ static void uinput_request_release_slot( 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. @@ -165,7 +162,7 @@ static int uinput_request_send(struct ui uinput_dev_event(udev->dev, EV_UINPUT, request->code, request->id); out: - mutex_unlock(&udev->mutex); + spin_unlock(&udev->state_lock); return retval; } @@ -174,6 +171,13 @@ static int uinput_request_submit(struct { 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; @@ -288,7 +292,14 @@ static void uinput_destroy_device(struct 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; @@ -365,7 +376,9 @@ static int uinput_create_device(struct u if (error) goto fail2; + spin_lock(&udev->state_lock); udev->state = UIST_CREATED; + spin_unlock(&udev->state_lock); return 0; @@ -383,6 +396,7 @@ static int uinput_open(struct inode *ino 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);