Re: [PATCH v3] usb: gadget: ffs: Fix sparse error

[Michal Nazarewicz]

On Wed, Dec 24 2014, Rohith Seelaboyina wrote:
> This patch fixes the sparse error in functionfs
> driver.
>
> drivers/usb/gadget/function/f_fs.c:400:44: error: bad
> constant experssion.
>
> Dynamic memory allocation through kcalloc is more safer
> than declaring variable array size, Fix this error by
> using kcalloc for memory allocation, Check if memory
> allocation is successful and return -ENOMEM on failure.
>
> Signed-off-by: Rohith Seelaboyina <rseelaboyina@xxxxxxxxxx>

This has already been addressed in a way that does not require dynamic
allocation: <https://lkml.org/lkml/2014/9/10/513>.  I'd rather patch
attached at the end would be applied.

> ---
>  drivers/usb/gadget/function/f_fs.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
> index 63314ede7ba6..8af3f7906c83 100644
> --- a/drivers/usb/gadget/function/f_fs.c
> +++ b/drivers/usb/gadget/function/f_fs.c
> @@ -397,10 +397,13 @@ static ssize_t __ffs_ep0_read_events(struct ffs_data *ffs, char __user *buf,
>  	 * We are holding ffs->ev.waitq.lock and ffs->mutex and we need
>  	 * to release them.
>  	 */
> -	struct usb_functionfs_event events[n];
>  	unsigned i = 0;
> +	int ret;
> +	struct usb_functionfs_event *events;
>  
> -	memset(events, 0, sizeof events);
> +	events = kcalloc(n, sizeof(*events), GFP_KERNEL);
> +	if (!events)
> +		return -ENOMEM;
>  
>  	do {
>  		events[i].type = ffs->ev.types[i];
> @@ -421,8 +424,10 @@ static ssize_t __ffs_ep0_read_events(struct ffs_data *ffs, char __user *buf,
>  	spin_unlock_irq(&ffs->ev.waitq.lock);
>  	mutex_unlock(&ffs->mutex);
>  
> -	return unlikely(__copy_to_user(buf, events, sizeof events))
> -		? -EFAULT : sizeof events;
> +	ret = unlikely(__copy_to_user(buf, events, n * sizeof(*events)))
> +		? -EFAULT : n * sizeof(*events);
> +	kfree(events);
> +	return ret;
>  }
>  
>  static ssize_t ffs_ep0_read(struct file *file, char __user *buf,
> -- 
> 1.9.1
>