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From: Arnd Bergmann <arnd@arndb.de>
To: Paul Osmialowski <p.osmialowsk@samsung.com>
Cc: Jonathan Corbet <corbet@lwn.net>,
        Andrew Morton <akpm@linux-foundation.org>,
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        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Shuah Khan <shuahkh@osg.samsung.com>
Subject: Re: [RFC v3 6/9] kmsg: add ioctl for adding and deleting kmsg* devices
Date: Mon, 19 Oct 2015 15:19:25 +0200
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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