From: Jimmy Hu Date: Thu, 25 Jun 2026 07:37:04 +0000 (+0800) Subject: usb: gadget: udc: Fix use-after-free in gadget_match_driver X-Git-Tag: v7.2-rc3~5^2~12 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=67e511d2989eb1c8c588b599ce2fcc6bb8e6f7ea;p=thirdparty%2Fkernel%2Flinux.git usb: gadget: udc: Fix use-after-free in gadget_match_driver The udc structure acts as the management structure for the gadget, but their lifecycles are decoupled. A race condition exists where usb_del_gadget() frees the udc memory (e.g., via mode-switch work) while gadget_match_driver() concurrently accesses the freed udc memory (e.g., via configfs), causing a Use-After-Free (UAF) that triggers a NULL pointer dereference when the freed memory is zeroed: [39430.908615][ T1171] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 [39430.911397][ T1171] pc : __pi_strcmp+0x20/0x140 [39430.911441][ T1171] lr : gadget_match_driver+0x34/0x60 ... [39430.911890][ T1171] usb_gadget_register_driver_owner+0x50/0xf8 [39430.911910][ T1171] gadget_dev_desc_UDC_store+0xf4/0x140 [39430.931308][ T1171] configfs_write_iter+0xec/0x134 [39430.957058][ T1171] Workqueue: events_freezable __dwc3_set_mode [39430.957287][ T1171] dwc3_gadget_exit+0x34/0x8c [39430.957304][ T1171] __dwc3_set_mode+0xc0/0x664 Fix this by ensuring the udc structure remains allocated until the gadget is released. To achieve this, introduce a new usb_gadget_release() routine to the core. When the gadget is added, usb_add_gadget() stores the gadget's release routine in the udc structure and takes a reference to the udc. When the gadget is released, usb_gadget_release() drops the reference to the udc and then calls the gadget's release routine. Suggested-by: Alan Stern Cc: stable Signed-off-by: Jimmy Hu Reviewed-by: Alan Stern Link: https://patch.msgid.link/20260625073705.803880-1-hhhuuu@google.com Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c index 60340ff9edbf..f6da12b553a0 100644 --- a/drivers/usb/gadget/udc/core.c +++ b/drivers/usb/gadget/udc/core.c @@ -31,8 +31,9 @@ static const struct bus_type gadget_bus_type; /** * struct usb_udc - describes one usb device controller * @driver: the gadget driver pointer. For use by the class code - * @dev: the child device to the actual controller * @gadget: the gadget. For use by the class code + * @gadget_release: the gadget's release routine + * @dev: the child device to the actual controller * @list: for use by the udc class driver * @vbus: for udcs who care about vbus status, this value is real vbus status; * for udcs who do not care about vbus status, this value is always true @@ -53,6 +54,7 @@ static const struct bus_type gadget_bus_type; struct usb_udc { struct usb_gadget_driver *driver; struct usb_gadget *gadget; + void (*gadget_release)(struct device *dev); struct device dev; struct list_head list; bool vbus; @@ -1362,6 +1364,17 @@ static void usb_udc_nop_release(struct device *dev) dev_vdbg(dev, "%s\n", __func__); } +static void usb_gadget_release(struct device *dev) +{ + struct usb_gadget *gadget = dev_to_usb_gadget(dev); + struct usb_udc *udc = gadget->udc; + /* Cache the gadget's release routine to prevent UAF */ + void (*release)(struct device *dev) = udc->gadget_release; + + put_device(&udc->dev); + release(dev); +} + /** * usb_initialize_gadget - initialize a gadget and its embedded struct device * @parent: the parent device to this udc. Usually the controller driver's @@ -1418,6 +1431,14 @@ int usb_add_gadget(struct usb_gadget *gadget) mutex_init(&udc->connect_lock); udc->started = false; + /* + * Align decoupled lifecycles: take a UDC reference to ensure it + * remains allocated until the gadget is released, requiring an + * override of the gadget's release routine to drop it. + */ + udc->gadget_release = gadget->dev.release; + gadget->dev.release = usb_gadget_release; + get_device(&udc->dev); mutex_lock(&udc_lock); list_add_tail(&udc->list, &udc_list); @@ -1462,6 +1483,12 @@ int usb_add_gadget(struct usb_gadget *gadget) mutex_lock(&udc_lock); list_del(&udc->list); mutex_unlock(&udc_lock); + /* + * Revert the override and drop the UDC reference to prevent + * leaking the UDC if the gadget was statically allocated. + */ + gadget->dev.release = udc->gadget_release; + put_device(&udc->dev); err_put_udc: put_device(&udc->dev);