Re: [PATCH V4 2/2] Move stack parameters for sed_ioctl to prevent oversized stack with CONFIG_KASAN

From: Christoph Hellwig
Date: Mon Feb 13 2017 - 02:54:32 EST

> int sed_ioctl(struct opal_dev *dev, unsigned int cmd, unsigned long ptr)
> {
> + void *ioctl_ptr;
> + int ret = -ENOTTY;
> void __user *arg = (void __user *)ptr;

Can we use this opportunity to clean up the usual ioctl argument mess.
Id say pass the "void __user *argp" argument already (nvme_ioctl should
have a local variable for it anyway), and then just rename ioctl_ptr
variable to the usual short p.

> + unsigned int cmd_size = _IOC_SIZE(cmd);

> + ioctl_ptr = memdup_user(arg, cmd_size);

cmd_size is only used once, so why not opencode the expression in the
argument to memdup_user.