disable_usb9pfs() frees the IN and OUT usb_request objects before it
disables the corresponding endpoints. If either request is still queued,
the later usb_ep_disable() call cancels the endpoint queue and the UDC
driver can still access the already freed request.

With dummy_hcd and KASAN, this is reproducible by queueing the OUT
request and then disconnecting the configfs gadget:

  BUG: KASAN: slab-use-after-free in dummy_disable+0x2b4/0x300
  Read of size 8 at addr ffff888009702400 by task sh/1
  usb_ep_disable+0x8e/0x1f0
  usb9pfs_func_unbind+0x193/0x350
  gadget_dev_desc_UDC_store+0x135/0x280

dummy_free_request() also warns because the request is freed while its
queue entry is still linked.

Disable both endpoints before freeing the request objects. This lets
usb_ep_disable() cancel any queued transfers and invoke the completion
callback while the request storage is still valid. The request objects
are then freed only after they have been removed from the endpoint
queues.

Fixes: a3be076dc174 ("net/9p/usbg: Add new usb gadget function transport")
Cc: stable@vger.kernel.org
Reported-by: Yizhou Zhao <zhaoyz24@mails.tsinghua.edu.cn>
Reported-by: Yuxiang Yang <yangyx22@mails.tsinghua.edu.cn>
Reported-by: Ao Wang <wangao@seu.edu.cn>
Reported-by: Xuewei Feng <fengxw06@126.com>
Reported-by: Qi Li <qli01@tsinghua.edu.cn>
Reported-by: Ke Xu <xuke@tsinghua.edu.cn>
Assisted-by: GLM:GLM-5.1
Signed-off-by: Yizhou Zhao <zhaoyz24@mails.tsinghua.edu.cn>
---
 net/9p/trans_usbg.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/9p/trans_usbg.c b/net/9p/trans_usbg.c
index 1ce70338999c..5d0d6add150e 100644
--- a/net/9p/trans_usbg.c
+++ b/net/9p/trans_usbg.c
@@ -278,6 +278,9 @@ static void disable_usb9pfs(struct f_usb9pfs *usb9pfs)
 	struct usb_composite_dev *cdev =
 		usb9pfs->function.config->cdev;
 
+	disable_ep(cdev, usb9pfs->in_ep);
+	disable_ep(cdev, usb9pfs->out_ep);
+
 	if (usb9pfs->in_req) {
 		usb_ep_free_request(usb9pfs->in_ep, usb9pfs->in_req);
 		usb9pfs->in_req = NULL;
@@ -287,9 +290,6 @@ static void disable_usb9pfs(struct f_usb9pfs *usb9pfs)
 		usb_ep_free_request(usb9pfs->out_ep, usb9pfs->out_req);
 		usb9pfs->out_req = NULL;
 	}
-
-	disable_ep(cdev, usb9pfs->in_ep);
-	disable_ep(cdev, usb9pfs->out_ep);
 	dev_dbg(&cdev->gadget->dev, "%s disabled\n",
 		usb9pfs->function.name);
 }
-- 
2.43.0