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 8C4AE337B81; Wed, 8 Apr 2026 18:49:27 +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=1775674167; cv=none; b=Of6mm4nYTM1XCVlZc/mf4St572k2+SGpkX4bqBdvKCphvRwv+C9Fbk7rqgQ0INLq9S8GcedmozsP0MWwRr/8ucTLaGciJmaW57oYWNo8A/th10pKsfKx3f92MTBNBrUx9LD5zbe69efNO5iYFAbea8IZbxxzcA7rd6MO4H7T+Rs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775674167; c=relaxed/simple; bh=QXK2YycZ9kaMrt9tRjtVdlVcGZUzo4oluyexFfIijGA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=oye70rC7lQMHfe1v4qJGhjJTvD7qUhVIMojl0C3G0Gg7MkbLqEqnMq8z88kn5trA9lIpdS9rITfhILVY1qHJMq13inHg+Tj5auYQN7Wxk+c5wG6N1Vpat+ZQK3qP5f9P6xa0a5zbYuIouOIG6vRPtJ44hpxZIm/8n3CTroriV30= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=SmQD47+A; 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="SmQD47+A" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 226CEC2BC9E; Wed, 8 Apr 2026 18:49:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1775674167; bh=QXK2YycZ9kaMrt9tRjtVdlVcGZUzo4oluyexFfIijGA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SmQD47+AesQiiYswKStCqz9J/hEVS8YsxExqAeAwUlDsuGKrcbq/kSuvMajFVrSmX nxYM6MRRAQ4/xNR34+YezztwBO1pJwtPpgUULg8W6u/nTHXViTNNZbnM4BvYLWT+oY WEXlCKYU8+fmPDJFVrnth8x34hE204ioFYZ2pRrQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Kuen-Han Tsai Subject: [PATCH 6.12 208/242] usb: gadget: f_subset: Fix net_device lifecycle with device_move Date: Wed, 8 Apr 2026 20:04:08 +0200 Message-ID: <20260408175934.866190697@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260408175927.064985309@linuxfoundation.org> References: <20260408175927.064985309@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 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kuen-Han Tsai commit 06524cd1c9011bee141a87e43ab878641ed3652b 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: 8cedba7c73af ("usb: gadget: f_subset: 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-v1-6-4886b578161b@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/usb/gadget/function/f_subset.c | 57 ++++++++++++++++----------------- drivers/usb/gadget/function/u_gether.h | 22 ++++++++---- 2 files changed, 44 insertions(+), 35 deletions(-) --- a/drivers/usb/gadget/function/f_subset.c +++ b/drivers/usb/gadget/function/f_subset.c @@ -299,25 +299,22 @@ geth_bind(struct usb_configuration *c, s struct usb_ep *ep; struct f_gether_opts *gether_opts; + struct net_device *net __free(detach_gadget) = NULL; gether_opts = container_of(f->fi, struct f_gether_opts, func_inst); - /* - * in drivers/usb/gadget/configfs.c:configfs_composite_bind() - * configurations are bound in sequence with list_for_each_entry, - * in each configuration its functions are bound in sequence - * with list_for_each_entry, so we assume no race condition - * with regard to gether_opts->bound access - */ - if (!gether_opts->bound) { - mutex_lock(&gether_opts->lock); - gether_set_gadget(gether_opts->net, cdev->gadget); - status = gether_register_netdev(gether_opts->net); - mutex_unlock(&gether_opts->lock); - if (status) - return status; - gether_opts->bound = true; - } + scoped_guard(mutex, &gether_opts->lock) + if (gether_opts->bind_count == 0 && !gether_opts->bound) { + if (!device_is_registered(&gether_opts->net->dev)) { + gether_set_gadget(gether_opts->net, cdev->gadget); + status = gether_register_netdev(gether_opts->net); + } else + status = gether_attach_gadget(gether_opts->net, cdev->gadget); + + if (status) + return status; + net = gether_opts->net; + } us = usb_gstrings_attach(cdev, geth_strings, ARRAY_SIZE(geth_string_defs)); @@ -330,20 +327,18 @@ geth_bind(struct usb_configuration *c, s /* allocate instance-specific interface IDs */ status = usb_interface_id(c, f); if (status < 0) - goto fail; + return status; subset_data_intf.bInterfaceNumber = status; - status = -ENODEV; - /* allocate instance-specific endpoints */ ep = usb_ep_autoconfig(cdev->gadget, &fs_subset_in_desc); if (!ep) - goto fail; + return -ENODEV; geth->port.in_ep = ep; ep = usb_ep_autoconfig(cdev->gadget, &fs_subset_out_desc); if (!ep) - goto fail; + return -ENODEV; geth->port.out_ep = ep; /* support all relevant hardware speeds... we expect that when @@ -361,21 +356,19 @@ geth_bind(struct usb_configuration *c, s status = usb_assign_descriptors(f, fs_eth_function, hs_eth_function, ss_eth_function, ss_eth_function); if (status) - goto fail; + return status; /* NOTE: all that is done without knowing or caring about * the network link ... which is unavailable to this code * until we're activated via set_alt(). */ + gether_opts->bind_count++; + retain_and_null_ptr(net); + DBG(cdev, "CDC Subset: IN/%s OUT/%s\n", geth->port.in_ep->name, geth->port.out_ep->name); return 0; - -fail: - ERROR(cdev, "%s: can't bind, err %d\n", f->name, status); - - return status; } static inline struct f_gether_opts *to_f_gether_opts(struct config_item *item) @@ -418,7 +411,7 @@ static void geth_free_inst(struct usb_fu struct f_gether_opts *opts; opts = container_of(f, struct f_gether_opts, func_inst); - if (opts->bound) + if (device_is_registered(&opts->net->dev)) gether_cleanup(netdev_priv(opts->net)); else free_netdev(opts->net); @@ -462,8 +455,16 @@ static void geth_free(struct usb_functio static void geth_unbind(struct usb_configuration *c, struct usb_function *f) { + struct f_gether_opts *opts; + + opts = container_of(f->fi, struct f_gether_opts, func_inst); + geth_string_defs[0].id = 0; usb_free_all_descriptors(f); + + opts->bind_count--; + if (opts->bind_count == 0 && !opts->bound) + gether_detach_gadget(opts->net); } static struct usb_function *geth_alloc(struct usb_function_instance *fi) --- a/drivers/usb/gadget/function/u_gether.h +++ b/drivers/usb/gadget/function/u_gether.h @@ -15,17 +15,25 @@ #include +/** + * struct f_gether_opts - subset function options + * @func_inst: USB function instance. + * @net: The net_device associated with the subset 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 subset function will register the net_device during its own + * bind phase. + * @bind_count: Tracks the number of configurations the subset 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_gether_opts { struct usb_function_instance func_inst; struct net_device *net; bool bound; - - /* - * 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. - */ + int bind_count; struct mutex lock; int refcnt; };