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

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Message-ID: <20140510193246.GA12079@thin>
Date:	Sat, 10 May 2014 12:32:46 -0700
From:	Josh Triplett <josh@...htriplett.org>
To:	Jann Horn <jann@...jh.net>
Cc:	Arnd Bergmann <arnd@...db.de>,
	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 Sat, May 10, 2014 at 09:07:42AM +0200, Jann Horn wrote:
> On Fri, May 09, 2014 at 12:19:16PM -0700, Josh Triplett wrote:
> > +	if (port > 65535)
> > +		return 0;
> > +	switch (count) {
> [...]
> > +	case 4:
> > +		if (__put_user(inl(port), buf) < 0)
> > +			return -EFAULT;
> 
> What if I attempt a four-byte read at 65535? That would access four
> out-of-bounds bytes, right?

No, it would do an ind instruction on port 65535.

- Josh Triplett
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