From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753723AbYHRKu4 (ORCPT ); Mon, 18 Aug 2008 06:50:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751083AbYHRKus (ORCPT ); Mon, 18 Aug 2008 06:50:48 -0400 Received: from mtagate3.uk.ibm.com ([195.212.29.136]:56590 "EHLO mtagate3.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751156AbYHRKur (ORCPT ); Mon, 18 Aug 2008 06:50:47 -0400 Message-ID: <48A95400.5050003@de.ibm.com> Date: Mon, 18 Aug 2008 12:50:40 +0200 From: Carsten Otte Reply-To: carsteno@de.ibm.com Organization: =?ISO-8859-1?Q?BM_Deutschland_Research_=26_Developm?= =?ISO-8859-1?Q?ent_GmbH_/_Vorsitzender_des_Aufsichtsrats=3A_?= =?ISO-8859-1?Q?Martin_Jetter=2CGesch=E4ftsf=FChrung=3A_Herbert_Kir?= =?ISO-8859-1?Q?cher=2CSitz_der_Gesellschaft=3A_B=F6blingen_/_R?= =?ISO-8859-1?Q?egistergericht=3A_Amtsgericht_Stuttgart=2C_HRB_24?= =?ISO-8859-1?Q?3294?= User-Agent: Mozilla-Thunderbird 2.0.0.16 (X11/20080724) MIME-Version: 1.0 To: Nick Piggin CC: Andrew Morton , borntrae@linux.vnet.ibm.com, Jared Hulbert , Linux Kernel Mailing List , Linux Memory Management List , Linus Torvalds , Hugh Dickins Subject: Re: [patch] mm: xip fix fault vs sparse page invalidate race References: <20080818053821.GA3011@wotan.suse.de> <20080818054409.GB3011@wotan.suse.de> In-Reply-To: <20080818054409.GB3011@wotan.suse.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Nick Piggin wrote: > XIP has a race between sparse pages being inserted into page tables, and > sparse pages being zapped when its time to put a non-sparse page in. > > What can happen is that a process can be left with a dangling sparse page > in a MAP_SHARED mapping, while the rest of the world sees the non-sparse > version. Ie. data corruption. > > Guard these operations with a seqlock, making fault-in-sparse-pages > the slowpath, and try-to-unmap-sparse-pages the fastpath. > > Signed-off-by: Nick Piggin Ouch. Acked-by: Carsten Otte From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from d06nrmr1407.portsmouth.uk.ibm.com (d06nrmr1407.portsmouth.uk.ibm.com [9.149.38.185]) by mtagate8.uk.ibm.com (8.13.8/8.13.8) with ESMTP id m7IAoiBj192580 for ; Mon, 18 Aug 2008 10:50:44 GMT Received: from d06av02.portsmouth.uk.ibm.com (d06av02.portsmouth.uk.ibm.com [9.149.37.228]) by d06nrmr1407.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v9.0) with ESMTP id m7IAoiop3248254 for ; Mon, 18 Aug 2008 11:50:44 +0100 Received: from d06av02.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av02.portsmouth.uk.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id m7IAoh5X003991 for ; Mon, 18 Aug 2008 11:50:44 +0100 Message-ID: <48A95400.5050003@de.ibm.com> Date: Mon, 18 Aug 2008 12:50:40 +0200 From: Carsten Otte Reply-To: carsteno@de.ibm.com MIME-Version: 1.0 Subject: Re: [patch] mm: xip fix fault vs sparse page invalidate race References: <20080818053821.GA3011@wotan.suse.de> <20080818054409.GB3011@wotan.suse.de> In-Reply-To: <20080818054409.GB3011@wotan.suse.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Andrew Morton , borntrae@linux.vnet.ibm.com, Jared Hulbert , Linux Kernel Mailing List , Linux Memory Management List , Linus Torvalds , Hugh Dickins List-ID: Nick Piggin wrote: > XIP has a race between sparse pages being inserted into page tables, and > sparse pages being zapped when its time to put a non-sparse page in. > > What can happen is that a process can be left with a dangling sparse page > in a MAP_SHARED mapping, while the rest of the world sees the non-sparse > version. Ie. data corruption. > > Guard these operations with a seqlock, making fault-in-sparse-pages > the slowpath, and try-to-unmap-sparse-pages the fastpath. > > Signed-off-by: Nick Piggin Ouch. Acked-by: Carsten Otte -- 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/ . Don't email: email@kvack.org