linux-kernel - Re: [PATCH] drivers/char/mem.c: Add /dev/ioports, supporting 16-bit and 32-bit ports

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Message-ID: <9233735.5FfZoZovqP@wuerfel>
Date:	Fri, 09 May 2014 21:58:43 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Josh Triplett <josh@...htriplett.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-api@...r.kernel.org
Subject: Re: [PATCH] drivers/char/mem.c: Add /dev/ioports, supporting 16-bit and 32-bit ports

On Friday 09 May 2014 12:19:16 Josh Triplett wrote:

> +	if (!access_ok(VERIFY_WRITE, buf, count))
> +		return -EFAULT;
> +	if (port > 65535)
> +		return 0;

This should probably test against IO_SPACE_LIMIT, which may be zero,
something larger than 65536 or even ULONG_MAX, depending on the
architecture.

In cases where this IO_SPACE_LIMIT is zero or ULONG_MAX, we should
probably disallow access completely. The former case is for architectures
that don't have any I/O ports, the other is either a mistake, or is
used when inb is defined as readb, and the port numbers are just virtual
addresses.

	Arnd
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