From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx153.postini.com [74.125.245.153]) by kanga.kvack.org (Postfix) with SMTP id 31A666B004A for ; Thu, 23 Feb 2012 13:44:57 -0500 (EST) From: Andi Kleen Subject: Re: [RFC][PATCH] fix move/migrate_pages() race on task struct References: <20120223180740.C4EC4156@kernel> Date: Thu, 23 Feb 2012 10:45:00 -0800 In-Reply-To: <20120223180740.C4EC4156@kernel> (Dave Hansen's message of "Thu, 23 Feb 2012 10:07:40 -0800") Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: cl@linux.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Dave Hansen writes: > sys_move_pages() and sys_migrate_pages() are a pretty nice copy > and paste job of each other. They both take a pid, find the task > struct, and then grab a ref on the mm. They both also do an > rcu_read_unlock() after they've taken the mm and then proceed to > access 'task'. I think this is a bug in both cases. Can we share code? > > This patch takes the pid-to-task code along with the credential > and security checks in sys_move_pages() and sys_migrate_pages() > and consolidates them. It now takes a task reference in > the new function and requires the caller to drop it. I > believe this resolves the race. Looks good to me. Reviewed-by: Andi Kleen BTW looks like we really need a better stress test for these syscalls. -Andi -- ak@linux.intel.com -- Speaking for myself only -- 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