Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932260AbaGaH0V (ORCPT ); Thu, 31 Jul 2014 03:26:21 -0400 Received: from mail-lb0-f172.google.com ([209.85.217.172]:58346 "EHLO mail-lb0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932174AbaGaH0T (ORCPT ); Thu, 31 Jul 2014 03:26:19 -0400 Date: Thu, 31 Jul 2014 11:26:17 +0400 From: Cyrill Gorcunov To: "Kirill A. Shutemov" Cc: Al Viro , David Howells , Peter Zijlstra , "Michael L. Semon" , Ingo Molnar , jason.low2@hp.com, Sasha Levin , Oleg Nesterov , "David S. Miller" , linux-kernel@vger.kernel.org Subject: Re: cred_guard_mutex vs seq_file::lock [was: Re: 3.14.0+/x86: lockdep and mutexes not getting along] Message-ID: <20140731072617.GK3212@moon> References: <20140410142918.GU11096@twins.programming.kicks-ass.net> <20140409121940.GA12890@node.dhcp.inet.fi> <26259.1397227827@warthog.procyon.org.uk> <20140411150724.GI18016@ZenIV.linux.org.uk> <20140730223130.GA22417@node.dhcp.inet.fi> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140730223130.GA22417@node.dhcp.inet.fi> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 31, 2014 at 01:31:30AM +0300, Kirill A. Shutemov wrote: ... > > > > *cringe* > > > > I don't like it. That really should be a responsiblity of specific ->show(); > > "I'm going to take that mutex, bugger off if we are in execve()" makes a lot > > more sense than having e.g. seq_read() care of that. IOW, I would very > > much prefer the patch you've sent last week. > > > > And yes, it might leave lockdep false positives, but that's better dealt with > > by annotating the sucker ("this guy has a separate lockdep class for its > > ->lock"). E.g. by splitting proc_single_file_operations in two and having > > the one used for those files do lockdep_set_class() in its ->open(). > > I've got annoyed by the lockdep warning. What about the patch below? > > From 54d8c463e12f23c09d6a2dbf93a4dc9bcb493c67 Mon Sep 17 00:00:00 2001 > From: "Kirill A. Shutemov" > Date: Thu, 31 Jul 2014 00:59:52 +0300 > Subject: [PATCH] procfs: silence lockdep warning about read vs. exec seq_file > > Testcase: > > cat /proc/self/maps >/dev/null > chmod +x /proc/self/net/packet > exec /proc/self/net/packet > > It triggers lockdep warning: ... > > It's a false positive: seq files which take cred_guard_mutex are never > executable. Let's use separate lock class for them. > > I don't know why we allow "chmod +x" on some proc files, notably net-related. > Is it a bug? > > Also I suspect eb94cd96e05d fixes non-existing bug, like this one. Yeah, it should. And the patch looks good to me. Still I think maybe indeed we need to prevent ability to set executable attribute on proc seq files? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/