From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx204.postini.com [74.125.245.204]) by kanga.kvack.org (Postfix) with SMTP id 6BEFD6B004D for ; Sun, 18 Dec 2011 17:48:35 -0500 (EST) Received: by qcsd17 with SMTP id d17so3430373qcs.14 for ; Sun, 18 Dec 2011 14:48:34 -0800 (PST) Message-ID: <4EEE6DC0.2030007@gmail.com> Date: Sun, 18 Dec 2011 17:48:32 -0500 From: KOSAKI Motohiro MIME-Version: 1.0 Subject: Re: [PATCH][RESEND] mm: Fix off-by-one bug in print_nodes_state References: <1324209529-15892-1-git-send-email-ozaki.ryota@gmail.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Ryota Ozaki , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , linux-mm@kvack.org, stable@kernel.org (12/18/11 5:44 PM), 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. So the issue here is that > print_nodes_state() returns a size that is off by one according to > 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. You can verify this very simply with strace. Usually, /sys files don't output trailing 'JPY0'. And, 'JPY0' is not regular io friendly. So I can imagine some careless programmer think it is garbage. Is there any benefit to show trailing 'JPY0'? -- 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