From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 BE81E3C3C0F; Thu, 16 Jul 2026 09:07:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784192857; cv=none; b=iBwwkfs6Pjp0iyGTUE6UHPSOgwrjcANJE/LnirzCqWZM/24RMo3yHZtqzkoq/HVxdPszpD2E5WPGOvHumZiuQgWhy7nmOqWSqaBJYLsHkFHP4egyQxfMnWGRb/RTcYwqU0O5/aimOlw/yQA5Z+kUs0o+qeTO/LcFFU5bgs42Yc4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784192857; c=relaxed/simple; bh=ZWMPoxE2yiQyHojiH+spTJ0cwmi+UJpfg8+HcAZljMY=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=G0MOIQXEV7oSjT+THsw06TvRl+UErp7tf5kUgbLqK0it/1LgLy9msy7kkiY+NUJWz93KwZDOK3ZOmn/w0uR7wp4cTYjyPiqPCIKTRAFi0W5bkaHiiciEL7y3V0IMj15ouefYiQGBNwfLih0ExixbGMbBGzdjtVjVNuSZOIe237k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YwHbz78r; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YwHbz78r" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EAEEB1F00A3A; Thu, 16 Jul 2026 09:07:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784192855; bh=IFFU4K3LexTGa/YWoLZlzdaOsd4usYxjWDL2XYq9O9I=; h=From:To:Subject:Date:In-Reply-To:References; b=YwHbz78rXkF8S5NOh8hjjbHtlJHILeBvHqkSsLmFAIDw/3pyIqfALQPVsjscdiNgB I/T8hCAMwn3LJlWymMYzTNM2lUYQgd8Tl/f1hXJnoXSkqlk4ntODtBi14kq74HOV+L Ky0T+1W9HCIaO/XsCKR1kaYZxO55CSmepTgRdxxzR5VvpQZkuqkjCsBdkBe3iMze1S yB7pA8eJDTJwCJ7vs5pWMAVIiPFn49IKJVvXsDi0xXX5ZHkIRXaA/bsk9WNxfPaPn4 VPzPezOQWWoS5CyciLINpSgfkS1dEgrZEwDmddn8JTVi1Az3cZCb3GyXogEX0La1so QqByWhmeO7IsA== From: Lee Jones To: lee@kernel.org, Ping Cheng , Jason Gerecke , Jiri Kosina , Benjamin Tissoires , Aaron Skomra , Dmitry Torokhov , Peter Hutterer , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v6 2/4] HID: wacom: Fix Use-After-Free in wacom_intuos_pad Date: Thu, 16 Jul 2026 09:07:13 +0000 Message-ID: <20260716090726.2711293-2-lee@kernel.org> X-Mailer: git-send-email 2.55.0.141.g00534a21ce-goog In-Reply-To: <20260716090726.2711293-1-lee@kernel.org> References: <20260716090726.2711293-1-lee@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit wacom_intuos_pad() accesses wacom->shared->touch_input locklessly inside the interrupt handler context. If the Touch sibling device is disconnected, wacom_remove_shared_data() clears 'touch_input' outside any lock, creating a Time-of-Check to Time-of-Use (TOCTOU) race condition where a preempted reader in interrupt context dereferences the freed pointer, leading to a Use-After-Free. Resolve this by introducing RCU protection for the touch_input pointer: - Annotate 'touch_input' in wacom_shared struct with __rcu - Wrap all lockless readers in wacom_wac.c with guard(rcu)() and rcu_dereference() using a unified wacom_report_touch_mute() helper - Update writers in wacom_sys.c using rcu_assign_pointer() - Call synchronize_rcu() in wacom_remove_shared_data() to ensure all active RCU readers have finished before the input device is freed Also wrap wacom_set_shared_values() and touch/pen assignments in wacom_add_shared_data() inside the wacom_udev_list_lock to serialize concurrent probe assignments, and verify that 'shared->touch == hdev' before setting touch_input to prevent concurrent sibling probe state desynchronization. Fixes: 961794a00eab ("Input: wacom - add reporting of SW_MUTE_DEVICE events") Signed-off-by: Lee Jones --- v1 -> v2: Split and use RCU as per Dmitry's review v2 -> v3: Sashiko fixes v3 -> v4: Dmitry's review [redundant check and guard()] v4 -> v5: Jason's review [split, remove "awkward if"] v5 -> v6: No change drivers/hid/wacom_sys.c | 35 +++++++++++++++++++++++------------ drivers/hid/wacom_wac.c | 36 ++++++++++++++++++------------------ drivers/hid/wacom_wac.h | 2 +- 3 files changed, 42 insertions(+), 31 deletions(-) diff --git a/drivers/hid/wacom_sys.c b/drivers/hid/wacom_sys.c index 6c2a3ddfe366..c6b37931d02d 100644 --- a/drivers/hid/wacom_sys.c +++ b/drivers/hid/wacom_sys.c @@ -875,10 +875,16 @@ static void wacom_remove_shared_data(void *res) data = container_of(wacom_wac->shared, struct wacom_hdev_data, shared); - if (wacom_wac->shared->touch == wacom->hdev) - wacom_wac->shared->touch = NULL; - else if (wacom_wac->shared->pen == wacom->hdev) - wacom_wac->shared->pen = NULL; + scoped_guard(mutex, &wacom_udev_list_lock) { + if (wacom_wac->shared->touch == wacom->hdev) { + wacom_wac->shared->touch = NULL; + rcu_assign_pointer(wacom_wac->shared->touch_input, NULL); + } else if (wacom_wac->shared->pen == wacom->hdev) { + wacom_wac->shared->pen = NULL; + } + } + + synchronize_rcu(); kref_put(&data->kref, wacom_release_shared_data); wacom_wac->shared = NULL; @@ -907,6 +913,11 @@ static int wacom_add_shared_data(struct hid_device *hdev) list_add_tail(&data->list, &wacom_udev_list); } + if (wacom_wac->features.device_type & WACOM_DEVICETYPE_TOUCH) + data->shared.touch = hdev; + else if (wacom_wac->features.device_type & WACOM_DEVICETYPE_PEN) + data->shared.pen = hdev; + mutex_unlock(&wacom_udev_list_lock); wacom_wac->shared = &data->shared; @@ -915,11 +926,6 @@ static int wacom_add_shared_data(struct hid_device *hdev) if (retval) return retval; - if (wacom_wac->features.device_type & WACOM_DEVICETYPE_TOUCH) - wacom_wac->shared->touch = hdev; - else if (wacom_wac->features.device_type & WACOM_DEVICETYPE_PEN) - wacom_wac->shared->pen = hdev; - return retval; } @@ -2343,9 +2349,15 @@ static void wacom_release_resources(struct wacom *wacom) static void wacom_set_shared_values(struct wacom_wac *wacom_wac) { + struct wacom *wacom = container_of(wacom_wac, struct wacom, wacom_wac); + + guard(mutex)(&wacom_udev_list_lock); + if (wacom_wac->features.device_type & WACOM_DEVICETYPE_TOUCH) { - wacom_wac->shared->type = wacom_wac->features.type; - wacom_wac->shared->touch_input = wacom_wac->touch_input; + if (wacom_wac->shared->touch == wacom->hdev) { + wacom_wac->shared->type = wacom_wac->features.type; + rcu_assign_pointer(wacom_wac->shared->touch_input, wacom_wac->touch_input); + } } if (wacom_wac->has_mute_touch_switch) { @@ -2358,7 +2370,6 @@ static void wacom_set_shared_values(struct wacom_wac *wacom_wac) if (wacom_wac->is_soft_touch_switch) wacom_wac->shared->is_touch_on = true; } - } static int wacom_parse_and_register(struct wacom *wacom, bool wireless) diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c index 32c4fd03479e..4ac4d0c19461 100644 --- a/drivers/hid/wacom_wac.c +++ b/drivers/hid/wacom_wac.c @@ -510,6 +510,18 @@ static void wacom_intuos_schedule_prox_event(struct wacom_wac *wacom_wac) } } +static void wacom_report_touch_mute(struct wacom_wac *wacom_wac, bool mute) +{ + struct input_dev *touch_input; + + guard(rcu)(); + touch_input = rcu_dereference(wacom_wac->shared->touch_input); + if (touch_input) { + input_report_switch(touch_input, SW_MUTE_DEVICE, mute); + input_sync(touch_input); + } +} + static int wacom_intuos_pad(struct wacom_wac *wacom) { struct wacom_features *features = &wacom->features; @@ -650,12 +662,8 @@ static int wacom_intuos_pad(struct wacom_wac *wacom) input_report_key(input, KEY_CONTROLPANEL, menu); input_report_key(input, KEY_INFO, info); - if (wacom->shared && wacom->shared->touch_input) { - input_report_switch(wacom->shared->touch_input, - SW_MUTE_DEVICE, - !wacom->shared->is_touch_on); - input_sync(wacom->shared->touch_input); - } + if (wacom->shared) + wacom_report_touch_mute(wacom, !wacom->shared->is_touch_on); input_report_abs(input, ABS_RX, strip1); input_report_abs(input, ABS_RY, strip2); @@ -2155,7 +2163,7 @@ static void wacom_wac_pad_event(struct hid_device *hdev, struct hid_field *field */ if ((equivalent_usage == WACOM_HID_WD_MUTE_DEVICE) || (equivalent_usage == WACOM_HID_WD_TOUCHONOFF)) { - if (wacom_wac->shared->touch_input) { + if (wacom_wac->shared) { bool *is_touch_on = &wacom_wac->shared->is_touch_on; if (equivalent_usage == WACOM_HID_WD_MUTE_DEVICE && value) @@ -2163,9 +2171,7 @@ static void wacom_wac_pad_event(struct hid_device *hdev, struct hid_field *field else if (equivalent_usage == WACOM_HID_WD_TOUCHONOFF) *is_touch_on = value; - input_report_switch(wacom_wac->shared->touch_input, - SW_MUTE_DEVICE, !(*is_touch_on)); - input_sync(wacom_wac->shared->touch_input); + wacom_report_touch_mute(wacom_wac, !(*is_touch_on)); } return; } @@ -3383,11 +3389,8 @@ static int wacom_wireless_irq(struct wacom_wac *wacom, size_t len) if ((wacom->shared->type == INTUOSHT || wacom->shared->type == INTUOSHT2) && - wacom->shared->touch_input && wacom->shared->touch_max) { - input_report_switch(wacom->shared->touch_input, - SW_MUTE_DEVICE, data[5] & 0x40); - input_sync(wacom->shared->touch_input); + wacom_report_touch_mute(wacom, data[5] & 0x40); } pid = get_unaligned_be16(&data[6]); @@ -3422,11 +3425,8 @@ static int wacom_status_irq(struct wacom_wac *wacom_wac, size_t len) if ((features->type == INTUOSHT || features->type == INTUOSHT2) && - wacom_wac->shared->touch_input && features->touch_max) { - input_report_switch(wacom_wac->shared->touch_input, - SW_MUTE_DEVICE, data[8] & 0x40); - input_sync(wacom_wac->shared->touch_input); + wacom_report_touch_mute(wacom_wac, data[8] & 0x40); } if (data[9] & 0x02) { /* wireless module is attached */ diff --git a/drivers/hid/wacom_wac.h b/drivers/hid/wacom_wac.h index 126bec6e5c0c..a8bbba4a6f37 100644 --- a/drivers/hid/wacom_wac.h +++ b/drivers/hid/wacom_wac.h @@ -285,7 +285,7 @@ struct wacom_shared { /* for wireless device to access USB interfaces */ unsigned touch_max; int type; - struct input_dev *touch_input; + struct input_dev __rcu *touch_input; struct hid_device *pen; struct hid_device *touch; bool has_mute_touch_switch; -- 2.55.0.141.g00534a21ce-goog