From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 9F7468D003B for ; Wed, 20 Apr 2011 16:24:37 -0400 (EDT) Received: from wpaz5.hot.corp.google.com (wpaz5.hot.corp.google.com [172.24.198.69]) by smtp-out.google.com with ESMTP id p3KKOWJ3009100 for ; Wed, 20 Apr 2011 13:24:32 -0700 Received: from pvg7 (pvg7.prod.google.com [10.241.210.135]) by wpaz5.hot.corp.google.com with ESMTP id p3KKOHuc027890 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=NOT) for ; Wed, 20 Apr 2011 13:24:30 -0700 Received: by pvg7 with SMTP id 7so743853pvg.23 for ; Wed, 20 Apr 2011 13:24:28 -0700 (PDT) Date: Wed, 20 Apr 2011 13:24:26 -0700 (PDT) From: David Rientjes Subject: Re: [PATCH 1/2] break out page allocation warning code In-Reply-To: <20110420093900.45F6.A69D9226@jp.fujitsu.com> Message-ID: References: <20110419094422.9375.A69D9226@jp.fujitsu.com> <20110420093900.45F6.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: KOSAKI Motohiro , John Stultz Cc: Dave Hansen , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Johannes Weiner , Michal Nazarewicz , Andrew Morton On Wed, 20 Apr 2011, KOSAKI Motohiro wrote: > > That was true a while ago, but you now need to protect every thread's > > ->comm with get_task_comm() or ensuring task_lock() is held to protect > > against /proc/pid/comm which can change other thread's ->comm. That was > > different before when prctl(PR_SET_NAME) would only operate on current, so > > no lock was needed when reading current->comm. > > Right. /proc/pid/comm is evil. We have to fix it. otherwise we need change > all of current->comm user. It's very lots! > Fixing it in this case would be removing it and only allowing it for current via the usual prctl() :) The code was introduced in 4614a696bd1c (procfs: allow threads to rename siblings via /proc/pid/tasks/tid/comm) in December 2009 and seems to originally be meant for debugging. We simply can't continue to let it modify any thread's ->comm unless we change the over 300 current->comm deferences in the kernel. I'd prefer that we remove /proc/pid/comm entirely or at least prevent writing to it unless CONFIG_EXPERT. -- 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