usb: gadget: f_rndis: Refactor bind path to use __free()

After an bind/unbind cycle, the rndis->notify_req is left stale. If a
subsequent bind fails, the unified error label attempts to free this
stale request, leading to a NULL pointer dereference when accessing
ep->ops->free_request.

Refactor the error handling in the bind path to use the __free()
automatic cleanup mechanism.

Fixes: 45fe3b8 ("usb ethernet gadget: split RNDIS function")
Cc: stable@kernel.org
Signed-off-by: Kuen-Han Tsai <khtsai@google.com>
Link: https://lore.kernel.org/r/20250916-ready-v1-6-4997bf277548@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20250916-ready-v1-6-4997bf277548@google.com

Author: Kuen-Han Tsai

drivers/usb/gadget/function/f_rndis.c

@@ -19,6 +19,8 @@
 
 #include <linux/atomic.h>
 
+#include <linux/usb/gadget.h>
+
 #include "u_ether.h"
 #include "u_ether_configfs.h"
 #include "u_rndis.h"
@@ -662,19 +664,18 @@ rndis_bind(struct usb_configuration *c, struct usb_function *f)
 	struct usb_ep		*ep;
 
 	struct f_rndis_opts *rndis_opts;
+	struct usb_os_desc_table        *os_desc_table __free(kfree) = NULL;
+	struct usb_request		*request __free(free_usb_request) = NULL;
 
 	if (!can_support_rndis(c))
 		return -EINVAL;
 
 	rndis_opts = container_of(f->fi, struct f_rndis_opts, func_inst);
 
 	if (cdev->use_os_string) {
-		f->os_desc_table = kzalloc(sizeof(*f->os_desc_table),
-					   GFP_KERNEL);
-		if (!f->os_desc_table)
+		os_desc_table = kzalloc(sizeof(*os_desc_table), GFP_KERNEL);
+		if (!os_desc_table)
 			return -ENOMEM;
-		f->os_desc_n = 1;
-		f->os_desc_table[0].os_desc = &rndis_opts->rndis_os_desc;
 	}
 
 	rndis_iad_descriptor.bFunctionClass = rndis_opts->class;
@@ -692,53 +693,45 @@ rndis_bind(struct usb_configuration *c, struct usb_function *f)
 		gether_set_gadget(rndis_opts->net, cdev->gadget);
 		status = gether_register_netdev(rndis_opts->net);
 		if (status)
-			goto fail;
+			return status;
 		rndis_opts->bound = true;
 	}
 
 	us = usb_gstrings_attach(cdev, rndis_strings,
 				 ARRAY_SIZE(rndis_string_defs));
-	if (IS_ERR(us)) {
-		status = PTR_ERR(us);
-		goto fail;
-	}
+	if (IS_ERR(us))
+		return PTR_ERR(us);
 	rndis_control_intf.iInterface = us[0].id;
 	rndis_data_intf.iInterface = us[1].id;
 	rndis_iad_descriptor.iFunction = us[2].id;
 
 	/* allocate instance-specific interface IDs */
 	status = usb_interface_id(c, f);
 	if (status < 0)
-		goto fail;
+		return status;
 	rndis->ctrl_id = status;
 	rndis_iad_descriptor.bFirstInterface = status;
 
 	rndis_control_intf.bInterfaceNumber = status;
 	rndis_union_desc.bMasterInterface0 = status;
 
-	if (cdev->use_os_string)
-		f->os_desc_table[0].if_id =
-			rndis_iad_descriptor.bFirstInterface;
-
 	status = usb_interface_id(c, f);
 	if (status < 0)
-		goto fail;
+		return status;
 	rndis->data_id = status;
 
 	rndis_data_intf.bInterfaceNumber = status;
 	rndis_union_desc.bSlaveInterface0 = status;
 
-	status = -ENODEV;
-
 	/* allocate instance-specific endpoints */
 	ep = usb_ep_autoconfig(cdev->gadget, &fs_in_desc);
 	if (!ep)
-		goto fail;
+		return -ENODEV;
 	rndis->port.in_ep = ep;
 
 	ep = usb_ep_autoconfig(cdev->gadget, &fs_out_desc);
 	if (!ep)
-		goto fail;
+		return -ENODEV;
 	rndis->port.out_ep = ep;
 
 	/* NOTE:  a status/notification endpoint is, strictly speaking,
@@ -747,21 +740,19 @@ rndis_bind(struct usb_configuration *c, struct usb_function *f)
 	 */
 	ep = usb_ep_autoconfig(cdev->gadget, &fs_notify_desc);
 	if (!ep)
-		goto fail;
+		return -ENODEV;
 	rndis->notify = ep;
 
-	status = -ENOMEM;
-
 	/* allocate notification request and buffer */
-	rndis->notify_req = usb_ep_alloc_request(ep, GFP_KERNEL);
-	if (!rndis->notify_req)
-		goto fail;
-	rndis->notify_req->buf = kmalloc(STATUS_BYTECOUNT, GFP_KERNEL);
-	if (!rndis->notify_req->buf)
-		goto fail;
-	rndis->notify_req->length = STATUS_BYTECOUNT;
-	rndis->notify_req->context = rndis;
-	rndis->notify_req->complete = rndis_response_complete;
+	request = usb_ep_alloc_request(ep, GFP_KERNEL);
+	if (!request)
+		return -ENOMEM;
+	request->buf = kmalloc(STATUS_BYTECOUNT, GFP_KERNEL);
+	if (!request->buf)
+		return -ENOMEM;
+	request->length = STATUS_BYTECOUNT;
+	request->context = rndis;
+	request->complete = rndis_response_complete;
 
 	/* support all relevant hardware speeds... we expect that when
 	 * hardware is dual speed, all bulk-capable endpoints work at
@@ -778,7 +769,7 @@ rndis_bind(struct usb_configuration *c, struct usb_function *f)
 	status = usb_assign_descriptors(f, eth_fs_function, eth_hs_function,
 			eth_ss_function, eth_ss_function);
 	if (status)
-		goto fail;
+		return status;
 
 	rndis->port.open = rndis_open;
 	rndis->port.close = rndis_close;
@@ -789,9 +780,18 @@ rndis_bind(struct usb_configuration *c, struct usb_function *f)
 	if (rndis->manufacturer && rndis->vendorID &&
 			rndis_set_param_vendor(rndis->params, rndis->vendorID,
 					       rndis->manufacturer)) {
-		status = -EINVAL;
-		goto fail_free_descs;
+		usb_free_all_descriptors(f);
+		return -EINVAL;
+	}
+
+	if (cdev->use_os_string) {
+		os_desc_table[0].os_desc = &rndis_opts->rndis_os_desc;
+		os_desc_table[0].if_id = rndis_iad_descriptor.bFirstInterface;
+		f->os_desc_table = no_free_ptr(os_desc_table);
+		f->os_desc_n = 1;
+
 	}
+	rndis->notify_req = no_free_ptr(request);
 
 	/* NOTE:  all that is done without knowing or caring about
 	 * the network link ... which is unavailable to this code
@@ -802,21 +802,6 @@ rndis_bind(struct usb_configuration *c, struct usb_function *f)
 			rndis->port.in_ep->name, rndis->port.out_ep->name,
 			rndis->notify->name);
 	return 0;
-
-fail_free_descs:
-	usb_free_all_descriptors(f);
-fail:
-	kfree(f->os_desc_table);
-	f->os_desc_n = 0;
-
-	if (rndis->notify_req) {
-		kfree(rndis->notify_req->buf);
-		usb_ep_free_request(rndis->notify, rndis->notify_req);
-	}
-
-	ERROR(cdev, "%s: can't bind, err %d\n", f->name, status);
-
-	return status;
 }
 
 void rndis_borrow_net(struct usb_function_instance *f, struct net_device *net)