From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756993AbaD1UVZ (ORCPT ); Mon, 28 Apr 2014 16:21:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33775 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754418AbaD1UVX (ORCPT ); Mon, 28 Apr 2014 16:21:23 -0400 Date: Mon, 28 Apr 2014 21:30:29 +0200 From: Oleg Nesterov To: Ingo Molnar , Hugh Dickins Cc: Ananth N Mavinakayanahalli , David Long , Peter Zijlstra , Srikar Dronamraju , linux-kernel@vger.kernel.org Subject: Re: [PATCH] uprobes: Refuse to insert a probe into MAP_SHARED vma Message-ID: <20140428193029.GA9773@redhat.com> References: <20140428191622.GA9234@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140428191622.GA9234@redhat.com> 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 And of course, I forgot to add Hugh ;) Fix that. On 04/28, Oleg Nesterov wrote: > > valid_vma() rejects the VM_SHARED vmas, but this still allows to insert > a probe into the MAP_SHARED but not VM_MAYWRITE vma. > > Currently this is fine, such a mapping doesn't really differ from the > private read-only mmap except mprotect(PROT_WRITE) won't work. However, > get_user_pages(FOLL_WRITE | FOLL_FORCE) doesn't allow to COW in this > case, and it would be safer to follow the same conventions as mm even > if currently this happens to work. > > After the recent cda540ace6a1 "mm: get_user_pages(write,force) refuse > to COW in shared areas" only uprobes can insert an anon page into the > shared file-backed area, lets stop this and change valid_vma() to check > VM_MAYSHARE instead. > > Signed-off-by: Oleg Nesterov > --- > kernel/events/uprobes.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c > index d1edc5e..7716c40 100644 > --- a/kernel/events/uprobes.c > +++ b/kernel/events/uprobes.c > @@ -127,7 +127,7 @@ struct xol_area { > */ > static bool valid_vma(struct vm_area_struct *vma, bool is_register) > { > - vm_flags_t flags = VM_HUGETLB | VM_MAYEXEC | VM_SHARED; > + vm_flags_t flags = VM_HUGETLB | VM_MAYEXEC | VM_MAYSHARE; > > if (is_register) > flags |= VM_WRITE; > -- > 1.5.5.1 >