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SubjectRe: [PATCH 4.19 093/125] usb: gadget: configfs: fix concurrent issue between composite APIs
On Mon 2019-11-11 19:28:52, Greg Kroah-Hartman wrote:
> From: Peter Chen <peter.chen@nxp.com>
>
> [ Upstream commit 1a1c851bbd706ea9f3a9756c2d3db28523506d3b ]
>
> We meet several NULL pointer issues if configfs_composite_unbind
> and composite_setup (or composite_disconnect) are running together.
> These issues occur when do the function switch stress test, the
> configfs_compsoite_unbind is called from user mode by
> echo "" to /sys/../UDC entry, and meanwhile, the setup interrupt
> or disconnect interrupt occurs by hardware. The composite_setup

> +++ b/drivers/usb/gadget/configfs.c
> @@ -61,6 +61,8 @@ struct gadget_info {
> bool use_os_desc;
> char b_vendor_code;
> char qw_sign[OS_STRING_QW_SIGN_LEN];
> + spinlock_t spinlock;
> + bool unbind;
> };
>
> static inline struct gadget_info *to_gadget_info(struct config_item *item)
> @@ -1244,6 +1246,7 @@ static int configfs_composite_bind(struct usb_gadget *gadget,
> int ret;
>
> /* the gi->lock is hold by the caller */
> + gi->unbind = 0;
> cdev->gadget = gadget;

Since variable is bool, I'd expect "= false" here?

> + unsigned long flags;
>
> /* the gi->lock is hold by the caller */

"is held".

> cdev = get_gadget_data(gadget);
> gi = container_of(cdev, struct gadget_info, cdev);
> + spin_lock_irqsave(&gi->spinlock, flags);
> + gi->unbind = 1;

= true;

> +static int configfs_composite_setup(struct usb_gadget *gadget,
> + const struct usb_ctrlrequest *ctrl)
> +{
> + struct usb_composite_dev *cdev;
> + struct gadget_info *gi;
> + unsigned long flags;
> + int ret;
> +
> + cdev = get_gadget_data(gadget);
> + if (!cdev)
> + return 0;
> +
> + gi = container_of(cdev, struct gadget_info, cdev);
> + spin_lock_irqsave(&gi->spinlock, flags);
> + cdev = get_gadget_data(gadget);

cdev already contains required value, why get it second time? (If it
needs to be done under lock, comment might be useful...)


Best regards,
Pavel

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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