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Message-ID: <aa34a68e-454d-a146-31db-848385960b84@collabora.com>
Date: Wed, 23 Nov 2022 13:19:35 +0100
From: Andrzej Pietrasiewicz <andrzej.p@...labora.com>
To: John Keeping <john@...anate.com>, linux-usb@...r.kernel.org
Cc: Fabien Chouteau <fabien.chouteau@...co.com>,
Peter Korsgaard <peter.korsgaard@...co.com>,
Felipe Balbi <balbi@...com>,
Andrzej Pietrasiewicz <andrzej.p@...sung.com>,
linux-kernel@...r.kernel.org,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Lee Jones <lee@...nel.org>,
Alan Stern <stern@...land.harvard.edu>
Subject: Re: [PATCH 3/3] usb: gadget: f_hid: tidy error handling in hidg_alloc
W dniu 22.11.2022 o 13:35, John Keeping pisze:
> Unify error handling at the end of the function, reducing the risk of
> missing something on one of the error paths.
>
> Moving the increment of opts->refcnt later means there is no need to
> decrement it on the error path and is safe as this is guarded by
> opts->lock which is held for this entire section.
>
> Signed-off-by: John Keeping <john@...anate.com>
Reviewed-by: Andrzej Pietrasiewicz <andrzej.p@...labora.com>
> ---
> drivers/usb/gadget/function/f_hid.c | 21 +++++++++++----------
> 1 file changed, 11 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/usb/gadget/function/f_hid.c b/drivers/usb/gadget/function/f_hid.c
> index 6be6009f911e..a8da3b4a2855 100644
> --- a/drivers/usb/gadget/function/f_hid.c
> +++ b/drivers/usb/gadget/function/f_hid.c
> @@ -1269,18 +1269,14 @@ static struct usb_function *hidg_alloc(struct usb_function_instance *fi)
> opts = container_of(fi, struct f_hid_opts, func_inst);
>
> mutex_lock(&opts->lock);
> - ++opts->refcnt;
>
> device_initialize(&hidg->dev);
> hidg->dev.release = hidg_release;
> hidg->dev.class = hidg_class;
> hidg->dev.devt = MKDEV(major, opts->minor);
> ret = dev_set_name(&hidg->dev, "hidg%d", opts->minor);
> - if (ret) {
> - --opts->refcnt;
> - mutex_unlock(&opts->lock);
> - return ERR_PTR(ret);
> - }
> + if (ret)
> + goto err_unlock;
>
> hidg->bInterfaceSubClass = opts->subclass;
> hidg->bInterfaceProtocol = opts->protocol;
> @@ -1291,14 +1287,13 @@ static struct usb_function *hidg_alloc(struct usb_function_instance *fi)
> opts->report_desc_length,
> GFP_KERNEL);
> if (!hidg->report_desc) {
> - put_device(&hidg->dev);
> - --opts->refcnt;
> - mutex_unlock(&opts->lock);
> - return ERR_PTR(-ENOMEM);
> + ret = -ENOMEM;
> + goto err_put_device;
> }
> }
> hidg->use_out_ep = !opts->no_out_endpoint;
>
> + ++opts->refcnt;
> mutex_unlock(&opts->lock);
>
> hidg->func.name = "hid";
> @@ -1313,6 +1308,12 @@ static struct usb_function *hidg_alloc(struct usb_function_instance *fi)
> hidg->qlen = 4;
>
> return &hidg->func;
> +
> +err_put_device:
> + put_device(&hidg->dev);
> +err_unlock:
> + mutex_unlock(&opts->lock);
> + return ERR_PTR(ret);
> }
>
> DECLARE_USB_FUNCTION_INIT(hid, hidg_alloc_inst, hidg_alloc);
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