From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756873Ab2GLF6F (ORCPT ); Thu, 12 Jul 2012 01:58:05 -0400 Received: from e1.ny.us.ibm.com ([32.97.182.141]:57511 "EHLO e1.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755450Ab2GLF6A (ORCPT ); Thu, 12 Jul 2012 01:58:00 -0400 Date: Thu, 12 Jul 2012 11:27:51 +0530 From: Srikar Dronamraju To: Oleg Nesterov Cc: Ingo Molnar , Ananth N Mavinakayanahalli , Anton Arapov , Peter Zijlstra , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/5] uprobes: suppress uprobe_munmap() from mmput() Message-ID: <20120712055750.GC3598@linux.vnet.ibm.com> Reply-To: Srikar Dronamraju References: <20120708202917.GA18188@redhat.com> <20120708203003.GA18226@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20120708203003.GA18226@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12071205-6078-0000-0000-00000D219A1F Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Oleg Nesterov [2012-07-08 22:30:03]: > uprobe_munmap() does get_user_pages() and it is also called from > the final mmput()->exit_mmap() path. This slows down exit/mmput() > for no reason, and I think it is simply dangerous/wrong to try to > fault-in a page into the dying mm. If nothing else, this happens > after the last sync_mm_rss(), afaics handle_mm_fault() can change > the task->rss_stat and make the subsequent check_mm() unhappy. > > Change uprobe_munmap() to check mm->mm_users != 0. > > Signed-off-by: Oleg Nesterov Acked-by: Srikar Dronamraju > --- > kernel/events/uprobes.c | 3 +++ > 1 files changed, 3 insertions(+), 0 deletions(-) > > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > index a93b6df..47c4e24 100644 > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -1082,6 +1082,9 @@ void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned lon > if (!atomic_read(&uprobe_events) || !valid_vma(vma, false)) > return; > > + if (!atomic_read(&vma->vm_mm->mm_users)) /* called by mmput() ? */ > + return; > + > if (!atomic_read(&vma->vm_mm->uprobes_state.count)) > return; > > -- > 1.5.5.1 >