Re: [RFC v3 6/9] kmsg: add ioctl for adding and deleting kmsg* devices

[Arnd Bergmann <arnd@arndb.de>]

On Monday 19 October 2015 14:58:20 Paul Osmialowski wrote:
> +
> +struct kmsg_cmd_buffer_add {
> +       size_t size;
> +       unsigned short mode;
> +       int minor;
> +} __attribute__((packed));
> +
> +#define KMSG_IOCTL_MAGIC       0xBB
> +
> +/*
> 

Try to avoid using packed unaligned data structures. Here I would
just use __u64 and __u32 members.

> +       case KMSG_CMD_BUFFER_ADD:
> +               if (copy_from_user(&size, argp, sizeof(size)))
> +                       return -EFAULT;
> +               argp += sizeof(size);
> +               if (copy_from_user(&mode, argp, sizeof(mode)))
> +                       return -EFAULT;

This is a rather unusual way to access the data. Just copy the
entire structure to the stack.

	Arnd