usb: gadget : fix use-after-free in composite_dev_cleanup()

1. In func configfs_composite_bind() -> composite_os_desc_req_prepare():
if kmalloc fails, the pointer cdev->os_desc_req will be freed but not
set to NULL. Then it will return a failure to the upper-level function.
2. in func configfs_composite_bind() -> composite_dev_cleanup():
it will checks whether cdev->os_desc_req is NULL. If it is not NULL, it
will attempt to use it.This will lead to a use-after-free issue.

BUG: KASAN: use-after-free in composite_dev_cleanup+0xf4/0x2c0
Read of size 8 at addr 0000004827837a00 by task init/1

CPU: 10 PID: 1 Comm: init Tainted: G           O      5.10.97-oh #1
 kasan_report+0x188/0x1cc
 __asan_load8+0xb4/0xbc
 composite_dev_cleanup+0xf4/0x2c0
 configfs_composite_bind+0x210/0x7ac
 udc_bind_to_driver+0xb4/0x1ec
 usb_gadget_probe_driver+0xec/0x21c
 gadget_dev_desc_UDC_store+0x264/0x27c

Fixes: 37a3a53 ("usb: gadget: OS Feature Descriptors support")
Cc: stable <stable@kernel.org>
Signed-off-by: Tao Xue <xuetao09@huawei.com>
Link: https://lore.kernel.org/r/20250721093908.14967-1-xuetao09@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/composite.c

@@ -2465,6 +2465,11 @@ int composite_os_desc_req_prepare(struct usb_composite_dev *cdev,
 	if (!cdev->os_desc_req->buf) {
 		ret = -ENOMEM;
 		usb_ep_free_request(ep0, cdev->os_desc_req);
+		/*
+		 * Set os_desc_req to NULL so that composite_dev_cleanup()
+		 * will not try to free it again.
+		 */
+		cdev->os_desc_req = NULL;
 		goto end;
 	}
 	cdev->os_desc_req->context = cdev;