[PATCH 6.18 148/198] usb: gadget: f_hid: dont call cdev_init while cdev in use

Greg Kroah-Hartman
2026-04-20T16:04:57Z

From: Michael Zimmermann <sigmaepsilon92@gmail.com>

commit 81ebd43cc0d6d106ce7b6ccbf7b5e40ca7f5503d upstream.

When calling unbind, then bind again, cdev_init reinitialized the cdev,
even though there may still be references to it. That's the case when
the /dev/hidg* device is still opened. This obviously unsafe behavior
like oopes.

This fixes this by using cdev_alloc to put the cdev on the heap. That
way, we can simply allocate a new one in hidg_bind.

Closes: https://lore.kernel.org/linux-usb/CAN9vWDKZn0Ts5JyV2_xcAmbnBEi0znMLg_USMFrShRryXrgWGQ@mail.gmail.com/T/#m2cb0dba3633b67b2a679c98499508267d1508881
Cc: stable <stable@kernel.org>
Signed-off-by: Michael Zimmermann <sigmaepsilon92@gmail.com>
Link: https://patch.msgid.link/20260327192209.59945-1-sigmaepsilon92@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/gadget/function/f_hid.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)

--- a/drivers/usb/gadget/function/f_hid.c
+++ b/drivers/usb/gadget/function/f_hid.c
@@ -106,7 +106,7 @@ struct f_hidg {
struct list_head report_list;

struct device dev;
- struct cdev cdev;
+ struct cdev *cdev;
struct usb_function func;

struct usb_ep *in_ep;
@@ -749,8 +749,9 @@ static int f_hidg_release(struct inode *

static int f_hidg_open(struct inode *inode, struct file *fd)
{
+ struct kobject *parent = inode->i_cdev->kobj.parent;
struct f_hidg *hidg =
- container_of(inode->i_cdev, struct f_hidg, cdev);
+ container_of(parent, struct f_hidg, dev.kobj);

fd->private_data = hidg;

@@ -1277,8 +1278,12 @@ static int hidg_bind(struct usb_configur
}

/* create char device */
- cdev_init(&hidg->cdev, &f_hidg_fops);
- status = cdev_device_add(&hidg->cdev, &hidg->dev);
+ hidg->cdev = cdev_alloc();
+ if (!hidg->cdev)
+ goto fail_free_all;
+ hidg->cdev->ops = &f_hidg_fops;
+
+ status = cdev_device_add(hidg->cdev, &hidg->dev);
if (status)
goto fail_free_all;

@@ -1580,7 +1585,7 @@ static void hidg_unbind(struct usb_confi
{
struct f_hidg *hidg = func_to_hidg(f);

- cdev_device_del(&hidg->cdev, &hidg->dev);
+ cdev_device_del(hidg->cdev, &hidg->dev);
destroy_workqueue(hidg->workqueue);
usb_free_all_descriptors(f);
}