From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755634Ab2GMIN7 (ORCPT ); Fri, 13 Jul 2012 04:13:59 -0400 Received: from e3.ny.us.ibm.com ([32.97.182.143]:47340 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754940Ab2GMINl (ORCPT ); Fri, 13 Jul 2012 04:13:41 -0400 Date: Fri, 13 Jul 2012 13:43:33 +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 4/5] uprobes: kill copy_vma()->uprobe_mmap() Message-ID: <20120713081333.GB4781@linux.vnet.ibm.com> Reply-To: Srikar Dronamraju References: <20120708202917.GA18188@redhat.com> <20120708203008.GA18236@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20120708203008.GA18236@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12071308-8974-0000-0000-00000B20187A Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Oleg Nesterov [2012-07-08 22:30:08]: > Kill copy_vma()->uprobe_mmap(new_vma), it is absolutely wrong. > > This new_vma was just initialized to represent the new unmapped area, > [vm_start, vm_end) was returned by get_unmapped_area() in the caller. > > This means that uprobe_mmap()->get_user_pages() will fail for sure, > simply because find_vma() can never succeed. And I verified that > sys_mremap()->mremap_to() indeed always fails with the wrong ENOMEM > code if [addr, addr+old_len] is probed. > > And why this uprobe_mmap() was added? I believe the intent was wrong. > Note that the caller is going to do move_page_tables(), all registered > uprobes are already faulted in, we only change the virtual addresses. > > NOTE: However, somehow we need to close the race with uprobe_register() > which relies on map_info->vaddr. This needs another fix I'll try to do > later. Probably we need uprobe_mmap() in move_vma() but we can not do > this right now, this can confuse uprobes_state.counter (which I still > hope we are going to kill). > > Signed-off-by: Oleg Nesterov Acked-by: Srikar Dronamraju > --- > mm/mmap.c | 3 --- > 1 files changed, 0 insertions(+), 3 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index 3edfcdf..e5a4614 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -2418,9 +2418,6 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap, > if (new_vma->vm_file) { > get_file(new_vma->vm_file); > > - if (uprobe_mmap(new_vma)) > - goto out_free_mempol; > - > if (vma->vm_flags & VM_EXECUTABLE) > added_exe_file_vma(mm); > } > -- > 1.5.5.1 >