Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932078AbbHXUoM (ORCPT ); Mon, 24 Aug 2015 16:44:12 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:38648 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750942AbbHXUoK (ORCPT ); Mon, 24 Aug 2015 16:44:10 -0400 Date: Mon, 24 Aug 2015 13:44:08 -0700 From: Andrew Morton To: Sean Fu Cc: "Eric W. Biederman" , Andrey Ryabinin , Ulrich Obergfell , "Steven Rostedt (Red Hat)" , Prarit Bhargava , Eric B Munson , "Paul E. McKenney" , Johannes Weiner , Thomas Gleixner , Don Zickus , Heinrich Schuchardt , David Rientjes , linux-kernel@vger.kernel.org Subject: Re: [PATCH] kernel/sysctl.c: If "count" including the terminating byte '\0' the write system call should retrun success. Message-Id: <20150824134408.be0ffaa654f7d26802119b81@linux-foundation.org> In-Reply-To: References: X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1405 Lines: 33 On Mon, 24 Aug 2015 23:33:58 +0800 Sean Fu wrote: > On Mon, Aug 24, 2015 at 8:27 PM, Eric W. Biederman > wrote: > > > > > > On August 24, 2015 1:56:13 AM PDT, Sean Fu wrote: > >>when the input argument "count" including the terminating byte "\0", > >>The write system call return EINVAL on proc file. > >>But it return success on regular file. > > > > Nonsense. It will write the '\0' to a regular file because it is just data. > > > > Integers in proc are more than data. > > > > So I see no justification for this change. > In fact, "write(fd, "1\0", 2)" on Integers proc file return success on > 2.6 kernel. I already tested it on 2.6.6.60 kernel. > > So, The latest behavior of "write(fd, "1\0", 2)" is different from old > kernel(2.6). > This maybe impact the compatibility of some user space program. 2.6 was a long time ago. If this behaviour change has happened in the last 1-2 kernel releases then there would be a case to consider making changes. But if the kernel has been this way for two years then it's too late to bother switching back to the old (and strange) behaviour. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/