Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965203AbaFXQyW (ORCPT ); Tue, 24 Jun 2014 12:54:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38490 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754829AbaFXQyP (ORCPT ); Tue, 24 Jun 2014 12:54:15 -0400 Date: Tue, 24 Jun 2014 18:52:16 +0200 From: Oleg Nesterov To: Kees Cook Cc: linux-kernel@vger.kernel.org, Andy Lutomirski , Alexei Starovoitov , "Michael Kerrisk (man-pages)" , Andrew Morton , Daniel Borkmann , Will Drewry , Julien Tinnes , David Drysdale , linux-api@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-mips@linux-mips.org, linux-arch@vger.kernel.org, linux-security-module@vger.kernel.org Subject: Re: [PATCH v7 3/9] seccomp: introduce writer locking Message-ID: <20140624165216.GA29272@redhat.com> References: <1403560693-21809-1-git-send-email-keescook@chromium.org> <1403560693-21809-4-git-send-email-keescook@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1403560693-21809-4-git-send-email-keescook@chromium.org> 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 Kees, I am still trying to force myself to read and try to understand what this series does ;) Just a minor nit so far. On 06/23, Kees Cook wrote: > > @@ -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? > @@ -524,6 +528,9 @@ static long seccomp_set_mode(unsigned long seccomp_mode, char __user *filter) > } > #endif > > + if (unlikely(!lock_task_sighand(current, &irqflags))) > + goto out_free; > + Unless this task is exiting (namely, it has already called exit_notify()), lock_task_sighand(current) must not fail. Looks like you can simly do spin_lock_irq(->siglock). 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/