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=1793831419; b=TfzZdLMza+XNvQU3mBTcKs5pQMdlXMQGBr4ReAGdM58GFUS54ngsIR96tnqfWn1xrJMv WcRMR339ctz9Wzv00hWpqQSuW2VlL4hqlBYXJZqdChnb6TlCKjkS7taiWWWrmu/1I15SN G68aYAtoTUSjx2j+WdL4OoV73NxTcF1hqgmqQln1I4PNN8UnYQUTloJf7RpmNvYrOmi4o +oanGxwpPVz7exwUYcjKLWYU5QY4QNuJWT5e0ObG0qY0Ta8kIVn7P8I8VrLXc1QPSbxZZ MQqnS4tvHSjYqnhRGi85aornJBCUImYxWlsQtmCYE0sHnPZLsj8SXVqpXfReaaWi8ig== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793831419; 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=hM9wr/TEka4WXuG4LzbuWHkFufYu6bF2LD1fE/v2V8A=; b=TFitXLSnSYIv44gyuSYFYQJAdZbZ9zJA8Q9GvySxiK5gsGFoZJ23Ebx9/CujMoezJozF o5pPk9VEdrwwDvInOFAz02dIAlDbBI5YZIT1Sd7zBfZFv64VTtJPRdoEYf5/lBsaO8pcw veTxIzDGQnVDtqBWCIJ4YqIvkAs+yVlNcZazjA6mqg77lZMN0HATpokD9gtHnL6R4+7ML 0yMOX2ipYHoJ08BKaDRL7R7ld91vUDQS6DgGo2cS9Vg5rb24r6gilG8qcH40jE8CmFU+e WGx7EJlzPowSTJslri9TvnqUKUQeBR2ROHpWhTlvc3EFM93P1lXmlEaZeA/8xLhyvfw== 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=pvLTZGAv; 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 14338606AB3E; Wed, 4 Nov 2026 22:30:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=pvLTZGAv Received: by smtp.kernel.org (Postfix) with ESMTPSA id 78B9A1F00A15; Wed, 4 Nov 2026 22:30:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793831418; bh=hM9wr/TEka4WXuG4LzbuWHkFufYu6bF2LD1fE/v2V8A=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=pvLTZGAvV1RtLcBK7AxF2LJ4ZNfWWhuEX7MU5MsyvfxMbwXh1ixFTBv0INPQOKQ39 IpmMixfY0rhd4EyQ1moh678cJTwbJfRKbe+eEg072DO3OOEL/evaSsiJ15glp5xA0G nwUPNknCF8dQ1LIDAr9tNR/kLNOzaXesYWzDxlIE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Lee Jones , Ping Cheng , Jiri Kosina Subject: [PATCH 6.18 0693/1005] HID: wacom: Fix Use-After-Free in wacom_bamboo_pad Date: Wed, 4 Nov 2026 16:07:06 -0500 Message-ID: <20261104211103.021802169@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261104211043.516122098@linuxfoundation.org> References: <20261104211043.516122098@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Lee Jones commit 3a523ecf9ac3fdd33f5eb31c43937ee44135395b upstream. wacom_bamboo_pad_pen_event() accesses wacom->shared->pen locklessly relative to wacom_remove_shared_data() which nullifies it. This can lead to a Use-After-Free if the sibling device is removed while events are being processed. Resolve this by introducing RCU protection for pen and touch pointers: - Annotate 'pen' and 'touch' in wacom_shared struct with __rcu. - Wrap lockless readers in wacom_bamboo_pad_pen_event() with rcu_read_lock() and rcu_dereference(). - Update writers in wacom_sys.c using rcu_assign_pointer(). - Use rcu_dereference_protected for comparisons under wacom_udev_list_lock. - Also use rcu_access_pointer in wacom_sibling_pending() and wacom_mode_change_work() to avoid warnings (while lockless access in the latter remains a pre-existing issue). Cc: stable@vger.kernel.org Fixes: 8c97a765467c ("HID: wacom: add full support of the Wacom Bamboo PAD") Signed-off-by: Lee Jones Acked-by: Ping Cheng Tested-by: Ping Cheng Signed-off-by: Jiri Kosina Signed-off-by: Greg Kroah-Hartman --- drivers/hid/wacom_sys.c | 40 ++++++++++++++++++++++++++-------------- drivers/hid/wacom_wac.c | 13 ++++++------- drivers/hid/wacom_wac.h | 4 ++-- 3 files changed, 34 insertions(+), 23 deletions(-) --- a/drivers/hid/wacom_sys.c +++ b/drivers/hid/wacom_sys.c @@ -881,11 +881,18 @@ static void wacom_remove_shared_data(voi shared); scoped_guard(mutex, &wacom_udev_list_lock) { - if (wacom_wac->shared->touch == wacom->hdev) { - wacom_wac->shared->touch = NULL; + struct hid_device *touch = + rcu_dereference_protected(wacom_wac->shared->touch, + lockdep_is_held(&wacom_udev_list_lock)); + struct hid_device *pen = + rcu_dereference_protected(wacom_wac->shared->pen, + lockdep_is_held(&wacom_udev_list_lock)); + + if (touch == wacom->hdev) { + rcu_assign_pointer(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; + } else if (pen == wacom->hdev) { + rcu_assign_pointer(wacom_wac->shared->pen, NULL); } } @@ -2366,14 +2373,17 @@ static void wacom_set_shared_values(stru } if (wacom_wac->features.device_type & WACOM_DEVICETYPE_TOUCH) { - if (wacom_wac->shared->touch == wacom->hdev || !wacom_wac->shared->touch) { + struct hid_device *touch = + rcu_dereference_protected(wacom_wac->shared->touch, + lockdep_is_held(&wacom_udev_list_lock)); + + if (touch == wacom->hdev || !touch) { wacom_wac->shared->type = wacom_wac->features.type; - wacom_wac->shared->touch = wacom->hdev; + rcu_assign_pointer(wacom_wac->shared->touch, wacom->hdev); rcu_assign_pointer(wacom_wac->shared->touch_input, wacom_wac->touch_input); } } else if (wacom_wac->features.device_type & WACOM_DEVICETYPE_PEN) { - /* Pairs with smp_load_acquire() in wacom_sibling_pending() */ - smp_store_release(&wacom_wac->shared->pen, wacom->hdev); + rcu_assign_pointer(wacom_wac->shared->pen, wacom->hdev); } } @@ -2389,8 +2399,7 @@ static bool wacom_sibling_pending(struct return false; if (wacom->wacom_wac.shared) { - /* Pairs with smp_store_release() in wacom_set_shared_values() */ - if (smp_load_acquire(&wacom->wacom_wac.shared->pen)) + if (rcu_access_pointer(wacom->wacom_wac.shared->pen)) return false; } @@ -2857,16 +2866,19 @@ static void wacom_mode_change_work(struc bool is_direct = wacom->wacom_wac.is_direct_mode; int error = 0; - if (shared->pen) { - wacom1 = hid_get_drvdata(shared->pen); + struct hid_device *pen = rcu_access_pointer(shared->pen); + struct hid_device *touch = rcu_access_pointer(shared->touch); + + if (pen) { + wacom1 = hid_get_drvdata(pen); wacom_release_resources(wacom1); hid_hw_stop(wacom1->hdev); wacom1->wacom_wac.has_mode_change = true; wacom1->wacom_wac.is_direct_mode = is_direct; } - if (shared->touch) { - wacom2 = hid_get_drvdata(shared->touch); + if (touch) { + wacom2 = hid_get_drvdata(touch); wacom_release_resources(wacom2); hid_hw_stop(wacom2->hdev); wacom2->wacom_wac.has_mode_change = true; --- a/drivers/hid/wacom_wac.c +++ b/drivers/hid/wacom_wac.c @@ -3307,6 +3307,7 @@ static int wacom_bpt_irq(struct wacom_wa static void wacom_bamboo_pad_pen_event(struct wacom_wac *wacom, unsigned char *data) { + struct hid_device *pen; unsigned char prefix; /* @@ -3319,13 +3320,11 @@ static void wacom_bamboo_pad_pen_event(s prefix = data[0]; data[0] = WACOM_REPORT_BPAD_PEN; - /* - * actually reroute the event. - * No need to check if wacom->shared->pen is valid, hid_input_report() - * will check for us. - */ - hid_input_report(wacom->shared->pen, HID_INPUT_REPORT, data, - WACOM_PKGLEN_PENABLED, 1); + guard(rcu)(); + pen = rcu_dereference(wacom->shared->pen); + if (pen) + hid_input_report(pen, HID_INPUT_REPORT, data, + WACOM_PKGLEN_PENABLED, 1); data[0] = prefix; } --- a/drivers/hid/wacom_wac.h +++ b/drivers/hid/wacom_wac.h @@ -286,8 +286,8 @@ struct wacom_shared { unsigned touch_max; int type; struct input_dev __rcu *touch_input; - struct hid_device *pen; - struct hid_device *touch; + struct hid_device __rcu *pen; + struct hid_device __rcu *touch; bool has_mute_touch_switch; bool is_touch_on; };