[PATCH 6.6.y] usb: gadget: f_hid: move list and spinlock inits from bind to alloc

[Sasha Levin <sashal@kernel.org>]

From: Michael Zimmermann <sigmaepsilon92@gmail.com>

[ Upstream commit 4e0a88254ad59f6c53a34bf5fa241884ec09e8b2 ]

There was an issue when you did the following:
- setup and bind an hid gadget
- open /dev/hidg0
- use the resulting fd in EPOLL_CTL_ADD
- unbind the UDC
- bind the UDC
- use the fd in EPOLL_CTL_DEL

When CONFIG_DEBUG_LIST was enabled, a list_del corruption was reported
within remove_wait_queue (via ep_remove_wait_queue). After some
debugging I found out that the queues, which f_hid registers via
poll_wait were the problem. These were initialized using
init_waitqueue_head inside hidg_bind. So effectively, the bind function
re-initialized the queues while there were still items in them.

The solution is to move the initialization from hidg_bind to hidg_alloc
to extend their lifetimes to the lifetime of the function instance.

Additionally, I found many other possibly problematic init calls in the
bind function, which I moved as well.

Signed-off-by: Michael Zimmermann <sigmaepsilon92@gmail.com>
Cc: stable <stable@kernel.org>
Link: https://patch.msgid.link/20260331184844.2388761-1-sigmaepsilon92@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/usb/gadget/function/f_hid.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/gadget/function/f_hid.c b/drivers/usb/gadget/function/f_hid.c
index d8dafebeabea4..2137513b23a08 100644
--- a/drivers/usb/gadget/function/f_hid.c
+++ b/drivers/usb/gadget/function/f_hid.c
@@ -1000,13 +1000,8 @@ static int hidg_bind(struct usb_configuration *c, struct usb_function *f)
 	if (status)
 		goto fail;
 
-	spin_lock_init(&hidg->write_spinlock);
 	hidg->write_pending = 1;
 	hidg->req = NULL;
-	spin_lock_init(&hidg->read_spinlock);
-	init_waitqueue_head(&hidg->write_queue);
-	init_waitqueue_head(&hidg->read_queue);
-	INIT_LIST_HEAD(&hidg->completed_out_req);
 
 	/* create char device */
 	cdev_init(&hidg->cdev, &f_hidg_fops);
@@ -1275,6 +1270,12 @@ static struct usb_function *hidg_alloc(struct usb_function_instance *fi)
 
 	mutex_lock(&opts->lock);
 
+	spin_lock_init(&hidg->write_spinlock);
+	spin_lock_init(&hidg->read_spinlock);
+	init_waitqueue_head(&hidg->write_queue);
+	init_waitqueue_head(&hidg->read_queue);
+	INIT_LIST_HEAD(&hidg->completed_out_req);
+
 	device_initialize(&hidg->dev);
 	hidg->dev.release = hidg_release;
 	hidg->dev.class = &hidg_class;
-- 
2.53.0