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=1794231564; b=IACN9Tu3ZKvr2lsMzPqJLs4HpqQOoP5zphTNWZuLyqnE+0fQle4lZnVC7ERmxF5ykDtU iF6e7PUz6Vu9zgx3jPvmt9Wz+P0UjWsTRVmalR58UI/42QbdELqcvRhDI1YhvF3iW/BRw b+5oLA3t6YDjD53iuGed+VSAkzImlGyfOmEJ+4ITOCfgImOylyIuBU0FJP3xn2NF91a44 EBVdxt5c3dVeaL664QC4mlWQ/YSnxv/ISV5B31SqCzQPpliSrZv1QfnYu/4pS+Zyx90uK DfSyihCWnLPEsszrRXY7x89OoockQrXNBVYTLD7NNsOXAiZ0/TSpjgByagdrIXOJcdA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794231564; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=9EeOB9u+/9zwiIE4qzGkedjBVs8MINTSV7waj5u02a8=; b=Yq7sSmf77rBSBeNK9INfa6gSuy/Ghdj9Fev6j5wkVgQKxLELe02OmdhNOxQt8XGI9pAO wUL0abR0j6eKPymjWnshlm4T64IXnY9Dp/cT5P4WeIFMqz3+KhBOwyTR8gIDMz25LEONw 2jIcvwGlph6AY0RNHz4FqmyvIXXTJF1vw56AZTnUpyMELvjd9OjFgbPTaDwBHpkmYJ+k+ cmerX146mFA7n2I2a2NSM+PaV8nPfUAyPy1TjPVy9GzJbr8Nq6Ido/FyzgJ3fSBzSRMZM ZM9FtfI9JatVettpFSMjiIjOlPcqeUqqFyNPTs/EwH3i9F0qLqYZYwA3D/KfXViLUpA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=DM14gBG5; 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 AB6E1606A338; Mon, 9 Nov 2026 13:39:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=DM14gBG5 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2FA6F1F0089F; Mon, 9 Nov 2026 13:39:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794231563; bh=9EeOB9u+/9zwiIE4qzGkedjBVs8MINTSV7waj5u02a8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=DM14gBG5jHclDjY0Pkk4xcff2oUoW6RZHDO7esJ5sBtC7qzKEWaYZc8uci1xgYev3 hKVHbinkFf++S9nUWcZoBArAsMp10Xzh8W6vhNvTMVcC33M8aP8j5VTyDhIZuvYqRo gCATQsDjSZdHrUIBFwCyD5SU4tJidgojqcmv10EACY+E/W8aKCiBPr456u23Shb9kj rUqSicm568UvVuQ88/pchRKCr3Nb//3eJGCwgfMDau3/xz3iymFDw7jvSXIvXXo8AZ KW2eXAhfnoWgTDcky61It+3067wjpYiG5bFnoZGdBUksT481mgoSbr6FpAUBoFxwNF 1uU9HfqiDXWSA== From: Lee Jones To: lee@kernel.org, Jiri Kosina , Benjamin Tissoires , Ping Cheng , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org, Jiri Kosina Subject: [STABLE v5.10 3/5] HID: wacom: Fix Use-After-Free in wacom_bamboo_pad Date: Mon, 9 Nov 2026 13:39:04 +0000 Message-ID: <20261109133911.3026622-4-lee@kernel.org> X-Mailer: git-send-email 2.56.0.506.g506a7eabc5-goog In-Reply-To: <20261109133911.3026622-1-lee@kernel.org> References: <20261109133911.3026622-1-lee@kernel.org> X-Mailing-List: linux-kernel@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 [ Upstream commit 3a523ecf9ac3fdd33f5eb31c43937ee44135395b ] 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 [Lee: Use explicit lock/unlock calls and top-of-block declarations in wacom_remove_shared_data() and wacom_bamboo_pad_pen_event() for -std=gnu89 compatibility, and adapt to res_wacom] Signed-off-by: Lee Jones --- drivers/hid/wacom_sys.c | 40 ++++++++++++++++++++++++++-------------- drivers/hid/wacom_wac.c | 14 +++++++------- drivers/hid/wacom_wac.h | 4 ++-- 3 files changed, 35 insertions(+), 23 deletions(-) diff --git a/drivers/hid/wacom_sys.c b/drivers/hid/wacom_sys.c index 94e12c56e040..465d075d16f9 100644 --- a/drivers/hid/wacom_sys.c +++ b/drivers/hid/wacom_sys.c @@ -882,15 +882,22 @@ static void wacom_remove_shared_data(void *res) struct wacom_wac *wacom_wac = &res_wacom->wacom_wac; if (wacom_wac->shared) { + struct hid_device *touch, *pen; + data = container_of(wacom_wac->shared, struct wacom_hdev_data, shared); mutex_lock(&wacom_udev_list_lock); - if (wacom_wac->shared->touch == res_wacom->hdev) { - wacom_wac->shared->touch = NULL; + touch = rcu_dereference_protected(wacom_wac->shared->touch, + lockdep_is_held(&wacom_udev_list_lock)); + pen = rcu_dereference_protected(wacom_wac->shared->pen, + lockdep_is_held(&wacom_udev_list_lock)); + + if (touch == res_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 == res_wacom->hdev) { - wacom_wac->shared->pen = NULL; + } else if (pen == res_wacom->hdev) { + rcu_assign_pointer(wacom_wac->shared->pen, NULL); } mutex_unlock(&wacom_udev_list_lock); @@ -2350,14 +2357,17 @@ static void wacom_set_shared_values(struct wacom_wac *wacom_wac) } 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); } } @@ -2373,8 +2383,7 @@ static bool wacom_sibling_pending(struct wacom *wacom) 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; } @@ -2844,16 +2853,19 @@ static void wacom_mode_change_work(struct work_struct *work) 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; diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c index 059572ea0509..4c7ad9dc543e 100644 --- a/drivers/hid/wacom_wac.c +++ b/drivers/hid/wacom_wac.c @@ -3203,6 +3203,7 @@ static int wacom_bpt_irq(struct wacom_wac *wacom, size_t len) static void wacom_bamboo_pad_pen_event(struct wacom_wac *wacom, unsigned char *data) { + struct hid_device *pen; unsigned char prefix; /* @@ -3215,13 +3216,12 @@ static void wacom_bamboo_pad_pen_event(struct wacom_wac *wacom, 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); + rcu_read_lock(); + pen = rcu_dereference(wacom->shared->pen); + if (pen) + hid_input_report(pen, HID_INPUT_REPORT, data, + WACOM_PKGLEN_PENABLED, 1); + rcu_read_unlock(); data[0] = prefix; } diff --git a/drivers/hid/wacom_wac.h b/drivers/hid/wacom_wac.h index 957247e6ba1c..56d54ac53b3d 100644 --- a/drivers/hid/wacom_wac.h +++ b/drivers/hid/wacom_wac.h @@ -287,8 +287,8 @@ 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; }; -- 2.56.0.506.g506a7eabc5-goog