From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794061559; b=qeai6rndUD98vPcZ3IdY5Nxf8Xw8Ff5bBhJ3GiiXHAeZRwdbQ4/p0scwz1eGxDppBR8a kNioWe9QXUpt5Kl1ZD7FDnsMKJOWQE0GGBuOUNnJKo4uwQaqq2fL9BK2XcA2gUX+JQw/1 r1sXux//Hv0yKGpZAFRT6AZslv7e1WE/rN91StzMratcjY8ZeytLiysnOA/K7x882hsfJ b4k2eEfuWjeVHhRAci7/m/khjJ/us9BGxnquprdHkegRFxhYJmzEKQP0tfPAgzFJ6hm8j 4qk/aPawqrmgdMSrhNesB++cARhIyIcVGM7huKtVsEzj/3OMSKfO23PNCClQ/YSHTUQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794061559; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=pGqxydarAvjO5y82vNGts6uXhKOyP2QeTSWZc8Sdj2o=; b=BoXUvQDswLjYpRs3MgI0usZq7b+8EImJcWjAq/FhZqG+/IHoMl1QC24IB6Aq5TZAJy8X 0d4ssFXX7PZ/V/fTARl83xPtSzz6InPauCT5hUuGtUCc2d7MXOI+DfD8ex3FboDlKivSF 6HwQtZ+nyUNxa6CZVZFJyhn3p02mKKFK+g/tI858wsLvggzd8SUKyO69Yl44pKeMPjKBL Y2HNHH0D+qoM3D3AP6D0d4fApJSoe5j8bK6wRuvv0UehH/ghHc7HH1112fh0Rwa6GbjAg mWkolEylhf8v2kSmUojaA/HEtDt3NVVh8m5sruU3zqrUj5Gzl+383T3ZXbJvg3nknAA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=KaWRiKnC; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2588A606A32E; Sat, 7 Nov 2026 14:25:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=KaWRiKnC Received: by smtp.kernel.org (Postfix) with ESMTPSA id D29431F008A1; Sat, 7 Nov 2026 14:25:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794061559; bh=pGqxydarAvjO5y82vNGts6uXhKOyP2QeTSWZc8Sdj2o=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=KaWRiKnCmX552VjXK6p0FWImPhBYMfdG9lDpn12DMkX1uwK5ncdUdlAl5YDOcsZGT J0VNAttzIlW1cMWukzy//DveNFMUmzUCoi72+N/5VQLgNvUkjbYWzkTNWWu44bs5Ua zHU4sfMrLkEMfWEfmriqBlykeWAmF4IubdVC7fn8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+563191a4939ddbfe73d4@syzkaller.appspotmail.com, Yousef Alhouseen , Jiri Kosina Subject: [PATCH 6.12 0640/1536] HID: hiddev: keep state alive through disconnect unlock Date: Sat, 7 Nov 2026 08:44:16 -0500 Message-ID: <20261107135015.508823751@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261107134957.653319350@linuxfoundation.org> References: <20261107134957.653319350@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yousef Alhouseen commit 03f449b5de36a25fc5eba7dabf2b4494389bdb91 upstream. mutex_unlock() clears the mutex owner before taking its wait lock. A thread spinning in the final hiddev file release can acquire existancelock after hiddev_disconnect() clears the owner, then free hiddev before the disconnecting thread reaches the mutex wait lock. This causes a use-after-free in the mutex slow unlock path. Give the connection and each open file an explicit reference. Drop each reference only after its existancelock critical section has completed, so neither unlock path can free the mutex while the other is still using it. Fixes: 079034073faf ("HID: hiddev cleanup -- handle all error conditions properly") Reported-by: syzbot+563191a4939ddbfe73d4@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=563191a4939ddbfe73d4 Cc: stable@vger.kernel.org Signed-off-by: Yousef Alhouseen Link: https://syzkaller.appspot.com/bug?extid=563191a4939ddbfe73d4 Signed-off-by: Jiri Kosina Signed-off-by: Greg Kroah-Hartman --- drivers/hid/usbhid/hiddev.c | 37 +++++++++++++++++++------------------ include/linux/hiddev.h | 2 ++ 2 files changed, 21 insertions(+), 18 deletions(-) --- a/drivers/hid/usbhid/hiddev.c +++ b/drivers/hid/usbhid/hiddev.c @@ -46,6 +46,12 @@ struct hiddev_list { struct mutex thread_lock; }; +static void hiddev_put(struct hiddev *hiddev) +{ + if (refcount_dec_and_test(&hiddev->refcount)) + kfree(hiddev); +} + /* * Find a report, given the report's type and ID. The ID can be specified * indirectly by REPORT_ID_FIRST (which returns the first report of the given @@ -216,26 +222,21 @@ static int hiddev_fasync(int fd, struct static int hiddev_release(struct inode * inode, struct file * file) { struct hiddev_list *list = file->private_data; + struct hiddev *hiddev = list->hiddev; unsigned long flags; - spin_lock_irqsave(&list->hiddev->list_lock, flags); + spin_lock_irqsave(&hiddev->list_lock, flags); list_del(&list->node); - spin_unlock_irqrestore(&list->hiddev->list_lock, flags); + spin_unlock_irqrestore(&hiddev->list_lock, flags); - mutex_lock(&list->hiddev->existancelock); - if (!--list->hiddev->open) { - if (list->hiddev->exist) { - hid_hw_close(list->hiddev->hid); - hid_hw_power(list->hiddev->hid, PM_HINT_NORMAL); - } else { - mutex_unlock(&list->hiddev->existancelock); - kfree(list->hiddev); - vfree(list); - return 0; - } + mutex_lock(&hiddev->existancelock); + if (!--hiddev->open && hiddev->exist) { + hid_hw_close(hiddev->hid); + hid_hw_power(hiddev->hid, PM_HINT_NORMAL); } - mutex_unlock(&list->hiddev->existancelock); + mutex_unlock(&hiddev->existancelock); + hiddev_put(hiddev); vfree(list); return 0; @@ -270,6 +271,7 @@ static int __hiddev_open(struct hiddev * spin_unlock_irq(&hiddev->list_lock); file->private_data = list; + refcount_inc(&hiddev->refcount); return 0; @@ -897,6 +899,7 @@ int hiddev_connect(struct hid_device *hi INIT_LIST_HEAD(&hiddev->list); spin_lock_init(&hiddev->list_lock); mutex_init(&hiddev->existancelock); + refcount_set(&hiddev->refcount, 1); hid->hiddev = hiddev; hiddev->hid = hid; hiddev->exist = 1; @@ -937,9 +940,7 @@ void hiddev_disconnect(struct hid_device if (hiddev->open) { hid_hw_close(hiddev->hid); wake_up_interruptible(&hiddev->wait); - mutex_unlock(&hiddev->existancelock); - } else { - mutex_unlock(&hiddev->existancelock); - kfree(hiddev); } + mutex_unlock(&hiddev->existancelock); + hiddev_put(hiddev); } --- a/include/linux/hiddev.h +++ b/include/linux/hiddev.h @@ -13,6 +13,7 @@ #ifndef _HIDDEV_H #define _HIDDEV_H +#include #include @@ -24,6 +25,7 @@ struct hiddev { int minor; int exist; int open; + refcount_t refcount; struct mutex existancelock; wait_queue_head_t wait; struct hid_device *hid;