From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx121.postini.com [74.125.245.121]) by kanga.kvack.org (Postfix) with SMTP id 11BBE6B004D for ; Mon, 19 Dec 2011 23:43:39 -0500 (EST) Received: by vcge1 with SMTP id e1so4784201vcg.14 for ; Mon, 19 Dec 2011 20:43:38 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: <1324209529-15892-1-git-send-email-ozaki.ryota@gmail.com> From: Ryota Ozaki Date: Tue, 20 Dec 2011 13:43:17 +0900 Message-ID: Subject: Re: [PATCH][RESEND] mm: Fix off-by-one bug in print_nodes_state Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: linux-kernel@vger.kernel.org, Greg Kroah-Hartman , linux-mm@kvack.org, stable@kernel.org Hi David, I'm so sorry for my late reply. On Mon, Dec 19, 2011 at 7:44 AM, David Rientjes wrote= : > On Sun, 18 Dec 2011, Ryota Ozaki wrote: > >> /sys/devices/system/node/{online,possible} involve a garbage byte >> because print_nodes_state returns content size + 1. To fix the bug, >> the patch changes the use of cpuset_sprintf_cpulist to follow the >> use at other places, which is clearer and safer. >> > > It's not a garbage byte, sysdev files use a buffer created with > get_zeroed_page(), so extra byte is guaranteed to be zero since > nodelist_scnprintf() won't write to it. =A0So the issue here is that > print_nodes_state() returns a size that is off by one according to I see. It's certainly not a garbage but just a zero-cleared byte. > ISO C99 although it won't cause a problem in practice. > >> This bug was introduced since v2.6.24. >> > > It's not a bug, the result of a 4-node system would be "0-3\n\0" and > returns 5 correctly. =A0You can verify this very simply with strace. Of course I confirmed the trailing '\0'. I'm sure it's not critical issue but it actually influences my script; I have to change from rstrip("\n") to rstrip("\n\0") in python. Yes, it's pretty trivial but enough to get rid of the extra for me :-) Anyway the subject and the comment of my patch need to be fixed. I'll send a revised one later. Thanks. ozaki-r -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org