Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754765AbaFXShd (ORCPT ); Tue, 24 Jun 2014 14:37:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54686 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752593AbaFXShb (ORCPT ); Tue, 24 Jun 2014 14:37:31 -0400 Date: Tue, 24 Jun 2014 20:35:50 +0200 From: Oleg Nesterov To: Kees Cook Cc: LKML , Andy Lutomirski , Alexei Starovoitov , "Michael Kerrisk (man-pages)" , Andrew Morton , Daniel Borkmann , Will Drewry , Julien Tinnes , David Drysdale , Linux API , "x86@kernel.org" , "linux-arm-kernel@lists.infradead.org" , linux-mips@linux-mips.org, linux-arch , linux-security-module Subject: Re: [PATCH v7 3/9] seccomp: introduce writer locking Message-ID: <20140624183550.GB1258@redhat.com> References: <1403560693-21809-1-git-send-email-keescook@chromium.org> <1403560693-21809-4-git-send-email-keescook@chromium.org> <20140624165216.GA29272@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/24, Kees Cook wrote: > > On Tue, Jun 24, 2014 at 9:52 AM, Oleg Nesterov wrote: > > Kees, > > > > I am still trying to force myself to read and try to understand what > > this series does ;) Just a minor nit so far. > > The use-case this solves is when a userspace process does not control > (or know) when a thread is spawned (e.g. via shared library init, or > LD_PRELOAD) but wants to make sure seccomp filters have been applied > to it. Yes, thanks, I understand this. But the details are not clear to me so far, I'll try to re-read this series later. > >> @@ -1142,6 +1168,7 @@ static struct task_struct *copy_process(unsigned long clone_flags, > >> { > >> int retval; > >> struct task_struct *p; > >> + unsigned long irqflags; > >> > >> if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) > >> return ERR_PTR(-EINVAL); > >> @@ -1196,7 +1223,6 @@ static struct task_struct *copy_process(unsigned long clone_flags, > >> goto fork_out; > >> > >> ftrace_graph_init_task(p); > >> - get_seccomp_filter(p); > >> > >> rt_mutex_init_task(p); > >> > >> @@ -1434,7 +1460,13 @@ static struct task_struct *copy_process(unsigned long clone_flags, > >> p->parent_exec_id = current->self_exec_id; > >> } > >> > >> - spin_lock(¤t->sighand->siglock); > >> + spin_lock_irqsave(¤t->sighand->siglock, irqflags); > >> + > >> + /* > >> + * Copy seccomp details explicitly here, in case they were changed > >> + * before holding tasklist_lock. > >> + */ > >> + copy_seccomp(p); > >> > >> /* > >> * Process group and session signals need to be delivered to just the > >> @@ -1446,7 +1478,7 @@ static struct task_struct *copy_process(unsigned long clone_flags, > >> */ > >> recalc_sigpending(); > >> if (signal_pending(current)) { > >> - spin_unlock(¤t->sighand->siglock); > >> + spin_unlock_irqrestore(¤t->sighand->siglock, irqflags); > >> write_unlock_irq(&tasklist_lock); > >> retval = -ERESTARTNOINTR; > >> goto bad_fork_free_pid; > >> @@ -1486,7 +1518,7 @@ static struct task_struct *copy_process(unsigned long clone_flags, > >> } > >> > >> total_forks++; > >> - spin_unlock(¤t->sighand->siglock); > >> + spin_unlock_irqrestore(¤t->sighand->siglock, irqflags); > >> write_unlock_irq(&tasklist_lock); > >> proc_fork_connector(p); > >> cgroup_post_fork(p); > > > > It seems that the only change copy_process() needs is copy_seccomp() under the locks. > > Everythinh else (irqflags games) looks obviously unneeded? > > I got irq lock dep warnings without these changes. With or without your patches? Could you show the waring? > If they're > unneeded, that's totally fine by me, but some change (either this or > markings to keep lockdep happy) is needed. Yes, we need to understand what what happens... Oleg. -- 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/