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=1793824313; b=F6x32pyK75e6aRoVUJqio7Klc+WbdM2waCzO9v6TxGAZEumTP9R1Vb4glECDNkZnhxxA GZhk/uB5mumBapQCVBZcwvW9HaymIkZGx2DSvQ4LlvjMLj+/LdHpObBEUx0wWZYHOp/S9 FfYKJL6F/DgZZoIdHtPXIYn0QYHIW9B+NZcaqWRExO/gl9911zBVWmv6UmM0aMmpBJTak SWDfNHgFsffv4N5VOqDVbfYMm260gSxKpKsXxB+YHSsrZdkv+7STGYdp337W/YtE88Wxu C8fFAZajVk19kRY2NYL9HMokKUQnaJp/Sj6/I/54T0bkpP4i2sFvuNMDQAjuEZpMlNA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793824313; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=EC0TjKzAX572QqvqWa+fnOyUGOVVYWeF17T5HQbHbD8=; b=iimSpYPUyjl4GsKmcxJ81+hZmWW+NUBNYu5dn2apuEXsrGRP2+eT5eD2BxNE6JqdMIWh m25i+8vfxmm9rfxHiYrbwoJp8Pump6iYD/WEmnmsf8/33sVzMQ+XhP7ZuvQz3sZ31i3cH JlGSK51YePWSsvIhG1Qzmdmqf389UHCeVtVmvQXtrav2OWdjy+0Lmzz4JNmCiBaR4XhJe dLgo8+uss87TDixFQDcNlPeGjPsmg1fwxL2haXpVLD90KWZoEzPIeTkk/F3UgZWStPNqx 9MDIeabqTab1L4/IQgrTrdWpQSyUVFPBK4aO5BxugAHhfz0ZzwpLxQG1pP3hrLVLMGA== 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=lXsQXi1d; 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 2F117606AB15 for ; Wed, 4 Nov 2026 20:31:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=lXsQXi1d Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3C4521F000C1; Wed, 4 Nov 2026 20:31:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793824312; bh=EC0TjKzAX572QqvqWa+fnOyUGOVVYWeF17T5HQbHbD8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=lXsQXi1dnswZVglXdLd3Mcvm0+GHaVFQqjxRT5HSRTPwZ4zz0qVZabZRx90wt8TO4 LZ5p+Tq+/5my5HexL13fmj2L43JfJPB1oOAbO7EymCDNZKJ9kl8U6QvCVOOYzhGqEb qPRSW4Lgv2XEigcToD5BRruWSgu78Z0SUB9GBK1YaSAbATrXndKwjEz2H5Cvc2yIKF b1vfaS6pNqviepLcWOkZvaMS+IZmwSNaMwyjd0BK8N88TTjEYfWcd9WvP7M/6/Ayi/ 9pfgHuFuDISw/eoFYAOtL4urlr2YcstKBDleKNC00p2hkRZ4FxhrkaX/l5aswIYz6P lTQpW//Ufnllw== From: Sasha Levin To: stable@vger.kernel.org Cc: Lee Jones , Ping Cheng , Jiri Kosina , Sasha Levin Subject: [PATCH 5.15.y] HID: wacom: Redesign shared sibling data lifecycle Date: Wed, 4 Nov 2026 15:31:51 -0500 Message-ID: <20261104203129.334404-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026110412-blanching-tweed-1612@gregkh> References: <2026110412-blanching-tweed-1612@gregkh> 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 From: Lee Jones [ Upstream commit 480c9cb14ae81f8e112ff83f8778b3d7b9324dc8 ] The Wacom driver coordinates state between sibling interfaces of the same physical device using a shared structure 'wacom_shared' inside 'wacom_hdev_data'. The driver kept a volatile representative pointer 'data->dev' pointing to a sibling 'hid_device' for physical path comparisons during sibling matching. This pointer management is fragile. When the representative device is disconnected, wacom_remove_shared_data() failed to clear/update 'data->dev', leading to a Use-After-Free vulnerability when subsequent sibling probes dereference the dangling 'data->dev' pointer. Resolve this issue by redesigning the sibling data lifecycle: - Eliminate the volatile 'data->dev' representative pointer completely - Redesign 'wacom_hdev_data' to store stable static copies of the required attributes upon first allocation: 'phys' path string, 'vendor', 'product' IDs and the sibling's 'device_type' - Use these static attributes for stable sibling matching in wacom_are_sibling() and wacom_get_hdev_data() This ensures sibling matching remains safe and stable even if individual siblings are dynamically added or removed. To secure the lifecycle against concurrent probe/disconnect races: - Switch kref_put() to kref_put_mutex() in wacom_remove_shared_data() to serialize refcount drops with list traversal and lookup - Modify wacom_release_shared_data() to assume the list lock is already held Also, do not accumulate the 'device_type' capability flag during subsequent sibling probes. Keeping only the first probed sibling's device_type exactly preserves the original sibling matching behavior without introducing side effects. Cc: stable@vger.kernel.org Fixes: 4492efffffeb ("Input: wacom - share pen info with touch of the same ID") Signed-off-by: Lee Jones Acked-by: Ping Cheng Tested-by: Ping Cheng Signed-off-by: Jiri Kosina [ sashal: Retained direct pointer cleanup in wacom_remove_shared_data() because the existing implementation lacks upstream RCU cleanup. ] Signed-off-by: Sasha Levin --- drivers/hid/wacom_sys.c | 70 +++++++++++++++++++++++++++-------------- 1 file changed, 46 insertions(+), 24 deletions(-) diff --git a/drivers/hid/wacom_sys.c b/drivers/hid/wacom_sys.c index b5e6605a83753..9f72b5c3ce95f 100644 --- a/drivers/hid/wacom_sys.c +++ b/drivers/hid/wacom_sys.c @@ -750,27 +750,47 @@ static void wacom_retrieve_hid_descriptor(struct hid_device *hdev, struct wacom_hdev_data { struct list_head list; struct kref kref; - struct hid_device *dev; + char phys[64]; + __u32 vendor; + __u32 product; + __u32 device_type; struct wacom_shared shared; }; +static bool wacom_compare_device_paths(struct hid_device *hdev_a, + const char *phys_b, char separator) +{ + const char *p1 = strrchr(hdev_a->phys, separator); + const char *p2 = strrchr(phys_b, separator); + int n1, n2; + + if (!p1 || !p2) + return false; + + n1 = p1 - hdev_a->phys; + n2 = p2 - phys_b; + + if (n1 != n2 || n1 <= 0 || n2 <= 0) + return false; + + return !strncmp(hdev_a->phys, phys_b, n1); +} + static LIST_HEAD(wacom_udev_list); static DEFINE_MUTEX(wacom_udev_list_lock); static bool wacom_are_sibling(struct hid_device *hdev, - struct hid_device *sibling) + struct wacom_hdev_data *data) { struct wacom *wacom = hid_get_drvdata(hdev); struct wacom_features *features = &wacom->wacom_wac.features; - struct wacom *sibling_wacom = hid_get_drvdata(sibling); - struct wacom_features *sibling_features = &sibling_wacom->wacom_wac.features; __u32 oVid = features->oVid ? features->oVid : hdev->vendor; __u32 oPid = features->oPid ? features->oPid : hdev->product; /* The defined oVid/oPid must match that of the sibling */ - if (features->oVid != HID_ANY_ID && sibling->vendor != oVid) + if (features->oVid != HID_ANY_ID && data->vendor != oVid) return false; - if (features->oPid != HID_ANY_ID && sibling->product != oPid) + if (features->oPid != HID_ANY_ID && data->product != oPid) return false; /* @@ -778,11 +798,11 @@ static bool wacom_are_sibling(struct hid_device *hdev, * device path, while those with different VID/PID must share * the same physical parent device path. */ - if (hdev->vendor == sibling->vendor && hdev->product == sibling->product) { - if (!hid_compare_device_paths(hdev, sibling, '/')) + if (hdev->vendor == data->vendor && hdev->product == data->product) { + if (!wacom_compare_device_paths(hdev, data->phys, '/')) return false; } else { - if (!hid_compare_device_paths(hdev, sibling, '.')) + if (!wacom_compare_device_paths(hdev, data->phys, '.')) return false; } @@ -795,7 +815,7 @@ static bool wacom_are_sibling(struct hid_device *hdev, * devices. */ if ((features->device_type & WACOM_DEVICETYPE_DIRECT) && - !(sibling_features->device_type & WACOM_DEVICETYPE_DIRECT)) + !(data->device_type & WACOM_DEVICETYPE_DIRECT)) return false; /* @@ -803,17 +823,17 @@ static bool wacom_are_sibling(struct hid_device *hdev, * devices. */ if (!(features->device_type & WACOM_DEVICETYPE_DIRECT) && - (sibling_features->device_type & WACOM_DEVICETYPE_DIRECT)) + (data->device_type & WACOM_DEVICETYPE_DIRECT)) return false; /* Pen devices may only be siblings of touch devices */ if ((features->device_type & WACOM_DEVICETYPE_PEN) && - !(sibling_features->device_type & WACOM_DEVICETYPE_TOUCH)) + !(data->device_type & WACOM_DEVICETYPE_TOUCH)) return false; /* Touch devices may only be siblings of pen devices */ if ((features->device_type & WACOM_DEVICETYPE_TOUCH) && - !(sibling_features->device_type & WACOM_DEVICETYPE_PEN)) + !(data->device_type & WACOM_DEVICETYPE_PEN)) return false; /* @@ -829,7 +849,7 @@ static struct wacom_hdev_data *wacom_get_hdev_data(struct hid_device *hdev) /* Try to find an already-probed interface from the same device */ list_for_each_entry(data, &wacom_udev_list, list) { - if (hid_compare_device_paths(hdev, data->dev, '/')) { + if (wacom_compare_device_paths(hdev, data->phys, '/')) { kref_get(&data->kref); return data; } @@ -837,7 +857,7 @@ static struct wacom_hdev_data *wacom_get_hdev_data(struct hid_device *hdev) /* Fallback to finding devices that appear to be "siblings" */ list_for_each_entry(data, &wacom_udev_list, list) { - if (wacom_are_sibling(hdev, data->dev)) { + if (wacom_are_sibling(hdev, data)) { kref_get(&data->kref); return data; } @@ -851,29 +871,28 @@ static void wacom_release_shared_data(struct kref *kref) struct wacom_hdev_data *data = container_of(kref, struct wacom_hdev_data, kref); - mutex_lock(&wacom_udev_list_lock); list_del(&data->list); - mutex_unlock(&wacom_udev_list_lock); - kfree(data); } static void wacom_remove_shared_data(void *res) { - struct wacom *wacom = res; + struct wacom *res_wacom = res; struct wacom_hdev_data *data; - struct wacom_wac *wacom_wac = &wacom->wacom_wac; + struct wacom_wac *wacom_wac = &res_wacom->wacom_wac; if (wacom_wac->shared) { data = container_of(wacom_wac->shared, struct wacom_hdev_data, shared); - if (wacom_wac->shared->touch == wacom->hdev) + if (wacom_wac->shared->touch == res_wacom->hdev) wacom_wac->shared->touch = NULL; - else if (wacom_wac->shared->pen == wacom->hdev) + else if (wacom_wac->shared->pen == res_wacom->hdev) wacom_wac->shared->pen = NULL; - kref_put(&data->kref, wacom_release_shared_data); + if (kref_put_mutex(&data->kref, wacom_release_shared_data, &wacom_udev_list_lock)) + mutex_unlock(&wacom_udev_list_lock); + wacom_wac->shared = NULL; } } @@ -896,7 +915,10 @@ static int wacom_add_shared_data(struct hid_device *hdev) } kref_init(&data->kref); - data->dev = hdev; + strscpy(data->phys, hdev->phys, sizeof(data->phys)); + data->vendor = hdev->vendor; + data->product = hdev->product; + data->device_type = wacom_wac->features.device_type; list_add_tail(&data->list, &wacom_udev_list); } -- 2.53.0