From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757623AbaEIUye (ORCPT ); Fri, 9 May 2014 16:54:34 -0400 Received: from terminus.zytor.com ([198.137.202.10]:51393 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757189AbaEIUyb (ORCPT ); Fri, 9 May 2014 16:54:31 -0400 Message-ID: <536D406D.2080508@zytor.com> Date: Fri, 09 May 2014 13:54:05 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Arnd Bergmann , Josh Triplett CC: Greg Kroah-Hartman , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org Subject: Re: [PATCH] drivers/char/mem.c: Add /dev/ioports, supporting 16-bit and 32-bit ports References: <20140509191914.GA7286@jtriplet-mobl1> <9233735.5FfZoZovqP@wuerfel> In-Reply-To: <9233735.5FfZoZovqP@wuerfel> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/09/2014 12:58 PM, Arnd Bergmann wrote: > 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. > PCI supports a 32-bit I/O address space, so if the architecture permits it, having a 32-bit I/O space is perfectly legitimate. It is worth noting that /dev/port has the same problem. However, if we're going to have these devices I'm wondering if having /dev/portw and /dev/portl (or something like that) might not make sense, rather than requiring a system call per transaction. Also, x86 supports unaligned I/O port references, but not all architectures do. On the other hand, x86 also supports ioperm(). -hpa