From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 74A67358363; Wed, 8 Apr 2026 19:02:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775674964; cv=none; b=MBx2XuJkKrVxf93kfuLgKsSaL5qyL3V3TiCLJYeBaHUXCms0lpEN244wdA/gxoYWtrRr6oMweB2k6X6xpF7KsESkJJXnO6s2pS11pxNQB+yIRzONln/ienVzAP5aOaBtWS5LdTL1GoGf3Lwb5ocz8YooqxPRR3vZ4LhQpTKWzng= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775674964; c=relaxed/simple; bh=Q23xmrC15Lxn63RuB9OsYd2qvh1ePp/2T+4/Nz645uI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uddr8OmjeWvhT3UHlOLPDwK48sWxCUTd2F7NpOjL0WzbLUHriBfxOddRqGm+0PQIFdbIBh8by3xSQpdfxvuzld0UxbzlM8pdS2vJu3xOWxNHDoXsDanbiSPUiJipJySBpoV4q3ztPxk9+MrydpoPlf0n65OImxQKC6Z8v8Ii3Ss= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=FsHoK6yC; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="FsHoK6yC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B881CC19421; Wed, 8 Apr 2026 19:02:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1775674964; bh=Q23xmrC15Lxn63RuB9OsYd2qvh1ePp/2T+4/Nz645uI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FsHoK6yCdNt3gUex/OwJC1Z9m4mIzhEDMiZtAek78aMM/u7isDCnFekrp5Lt7TblA jbmsYfCc6GTnwvh4Geumi5m9o009keLDh8paX6L3wN+g7xYtdhlfbavjrttCeSULOt PqFQEOUTO/yhwALd+t8Tnb2i0jOxDoM2WGwK62NY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Kuen-Han Tsai Subject: [PATCH 6.19 301/311] usb: gadget: f_ecm: Fix net_device lifecycle with device_move Date: Wed, 8 Apr 2026 20:05:01 +0200 Message-ID: <20260408175950.609461339@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260408175939.393281918@linuxfoundation.org> References: <20260408175939.393281918@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kuen-Han Tsai commit b2cc4fae67a51f60d81d6af2678696accb07c656 upstream. The net_device is allocated during function instance creation and registered during the bind phase with the gadget device as its sysfs parent. When the function unbinds, the parent device is destroyed, but the net_device survives, resulting in dangling sysfs symlinks: console:/ # ls -l /sys/class/net/usb0 lrwxrwxrwx ... /sys/class/net/usb0 -> /sys/devices/platform/.../gadget.0/net/usb0 console:/ # ls -l /sys/devices/platform/.../gadget.0/net/usb0 ls: .../gadget.0/net/usb0: No such file or directory Use device_move() to reparent the net_device between the gadget device tree and /sys/devices/virtual across bind and unbind cycles. During the final unbind, calling device_move(NULL) moves the net_device to the virtual device tree before the gadget device is destroyed. On rebinding, device_move() reparents the device back under the new gadget, ensuring proper sysfs topology and power management ordering. To maintain compatibility with legacy composite drivers (e.g., multi.c), the bound flag is used to indicate whether the network device is shared and pre-registered during the legacy driver's bind phase. Fixes: fee562a6450b ("usb: gadget: f_ecm: convert to new function interface with backward compatibility") Cc: stable@vger.kernel.org Signed-off-by: Kuen-Han Tsai Link: https://patch.msgid.link/20260320-usb-net-lifecycle-v1-4-4886b578161b@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/usb/gadget/function/f_ecm.c | 37 +++++++++++++++++++++++------------- drivers/usb/gadget/function/u_ecm.h | 21 ++++++++++++++------ 2 files changed, 39 insertions(+), 19 deletions(-) --- a/drivers/usb/gadget/function/f_ecm.c +++ b/drivers/usb/gadget/function/f_ecm.c @@ -681,6 +681,7 @@ ecm_bind(struct usb_configuration *c, st struct usb_ep *ep; struct f_ecm_opts *ecm_opts; + struct net_device *net __free(detach_gadget) = NULL; struct usb_request *request __free(free_usb_request) = NULL; if (!can_support_ecm(cdev->gadget)) @@ -688,18 +689,18 @@ ecm_bind(struct usb_configuration *c, st ecm_opts = container_of(f->fi, struct f_ecm_opts, func_inst); - mutex_lock(&ecm_opts->lock); - - gether_set_gadget(ecm_opts->net, cdev->gadget); - - if (!ecm_opts->bound) { - status = gether_register_netdev(ecm_opts->net); - ecm_opts->bound = true; - } - - mutex_unlock(&ecm_opts->lock); - if (status) - return status; + scoped_guard(mutex, &ecm_opts->lock) + if (ecm_opts->bind_count == 0 && !ecm_opts->bound) { + if (!device_is_registered(&ecm_opts->net->dev)) { + gether_set_gadget(ecm_opts->net, cdev->gadget); + status = gether_register_netdev(ecm_opts->net); + } else + status = gether_attach_gadget(ecm_opts->net, cdev->gadget); + + if (status) + return status; + net = ecm_opts->net; + } ecm_string_defs[1].s = ecm->ethaddr; @@ -790,6 +791,9 @@ ecm_bind(struct usb_configuration *c, st ecm->notify_req = no_free_ptr(request); + ecm_opts->bind_count++; + retain_and_null_ptr(net); + DBG(cdev, "CDC Ethernet: IN/%s OUT/%s NOTIFY/%s\n", ecm->port.in_ep->name, ecm->port.out_ep->name, ecm->notify->name); @@ -836,7 +840,7 @@ static void ecm_free_inst(struct usb_fun struct f_ecm_opts *opts; opts = container_of(f, struct f_ecm_opts, func_inst); - if (opts->bound) + if (device_is_registered(&opts->net->dev)) gether_cleanup(netdev_priv(opts->net)); else free_netdev(opts->net); @@ -906,9 +910,12 @@ static void ecm_free(struct usb_function static void ecm_unbind(struct usb_configuration *c, struct usb_function *f) { struct f_ecm *ecm = func_to_ecm(f); + struct f_ecm_opts *ecm_opts; DBG(c->cdev, "ecm unbind\n"); + ecm_opts = container_of(f->fi, struct f_ecm_opts, func_inst); + usb_free_all_descriptors(f); if (atomic_read(&ecm->notify_count)) { @@ -918,6 +925,10 @@ static void ecm_unbind(struct usb_config kfree(ecm->notify_req->buf); usb_ep_free_request(ecm->notify, ecm->notify_req); + + ecm_opts->bind_count--; + if (ecm_opts->bind_count == 0 && !ecm_opts->bound) + gether_detach_gadget(ecm_opts->net); } static struct usb_function *ecm_alloc(struct usb_function_instance *fi) --- a/drivers/usb/gadget/function/u_ecm.h +++ b/drivers/usb/gadget/function/u_ecm.h @@ -15,17 +15,26 @@ #include +/** + * struct f_ecm_opts - ECM function options + * @func_inst: USB function instance. + * @net: The net_device associated with the ECM function. + * @bound: True if the net_device is shared and pre-registered during the + * legacy composite driver's bind phase (e.g., multi.c). If false, + * the ECM function will register the net_device during its own + * bind phase. + * @bind_count: Tracks the number of configurations the ECM function is + * bound to, preventing double-registration of the @net device. + * @lock: Protects the data from concurrent access by configfs read/write + * and create symlink/remove symlink operations. + * @refcnt: Reference counter for the function instance. + */ struct f_ecm_opts { struct usb_function_instance func_inst; struct net_device *net; bool bound; + int bind_count; - /* - * Read/write access to configfs attributes is handled by configfs. - * - * This is to protect the data from concurrent access by read/write - * and create symlink/remove symlink. - */ struct mutex lock; int refcnt; };