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SubjectRe: [PATCH V4 04/12] misc: xilinx_sdfec: Add open, close and ioctl
On Sat, May 25, 2019 at 12:37:17PM +0100, Dragan Cvetic wrote:
> +static int xsdfec_dev_open(struct inode *iptr, struct file *fptr)
> +{
> + return 0;
> +}
> +
> +static int xsdfec_dev_release(struct inode *iptr, struct file *fptr)
> +{
> + return 0;
> +}

empty open/close functions are never needed, just drop them.

> +
> +static long xsdfec_dev_ioctl(struct file *fptr, unsigned int cmd,
> + unsigned long data)
> +{
> + struct xsdfec_dev *xsdfec;
> + void __user *arg = NULL;
> + int rval = -EINVAL;
> +
> + xsdfec = container_of(fptr->private_data, struct xsdfec_dev, miscdev);
> + if (!xsdfec)
> + return rval;

It is impossible for container_of() to return NULL, unless something
very magical and rare just happened. It's just doing pointer math, you
can never check the return value of it.

> +
> + if (_IOC_TYPE(cmd) != XSDFEC_MAGIC)
> + return -ENOTTY;

How can this happen?

> +
> + /* check if ioctl argument is present and valid */
> + if (_IOC_DIR(cmd) != _IOC_NONE) {
> + arg = (void __user *)data;
> + if (!arg)
> + return rval;
> + }
> +
> + switch (cmd) {
> + default:
> + /* Should not get here */
> + dev_warn(xsdfec->dev, "Undefined SDFEC IOCTL");

Nice that userspace has a way to fill up the kernel log :(

Just return the correct error here, don't log it.

thanks,

greg k-h

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