From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754162Ab2G3NWZ (ORCPT ); Mon, 30 Jul 2012 09:22:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44740 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753479Ab2G3NWY (ORCPT ); Mon, 30 Jul 2012 09:22:24 -0400 Message-ID: <50168A80.10805@redhat.com> Date: Mon, 30 Jul 2012 09:22:08 -0400 From: William Cohen User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.6esrpre) Gecko/20120714 Thunderbird/10.0.6 MIME-Version: 1.0 To: Oleg Nesterov CC: Ingo Molnar , Anton Arapov , "Frank Ch. Eigler" , Peter Zijlstra , Srikar Dronamraju , linux-kernel@vger.kernel.org Subject: Re: [PATCH] uprobes: mmap_region() corrupts mm->mm_rb if uprobe_mmap() fails References: <20120728163157.GA22719@redhat.com> In-Reply-To: <20120728163157.GA22719@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/28/2012 12:31 PM, Oleg Nesterov wrote: > https://bugzilla.redhat.com/show_bug.cgi?id=843640 Hi Oleg, I checked the following patch and it does fix the problem on the 3.5.0+ kernel. -Will > > If mmap_region()->uprobe_mmap() fails, unmap_and_free_vma path > does unmap_region() but does not remove the soon-to-be-freed vma > from rb tree (actually there are more problems). > > Perhaps we could do do_munmap() + return in this case, but in fact > it is simply wrong to abort if uprobe_mmap() fails. Until at least > we move the !UPROBE_COPY_INSN code from install_breakpoint() to > uprobe_register(). > > For example, uprobe_mmap()->install_breakpoint() can fail if the > probed insn is not supported (remember, uprobe_register() succeeds > if nobody mmaps inode/offset), mmap() should not fail in this case. > > dup_mmap()->uprobe_mmap() is wrong too by the same reason, fork() > can race with uprobe_register() and fail for no reason if it wins > the race and does install_breakpoint() first. > > Change mmap_region() and dup_mmap() to ignore the error code from > uprobe_mmap(). > > Reported-by: William Cohen > Signed-off-by: Oleg Nesterov > Cc: # v3.5 > --- > kernel/fork.c | 4 ++-- > mm/mmap.c | 5 ++--- > 2 files changed, 4 insertions(+), 5 deletions(-) > > diff --git a/kernel/fork.c b/kernel/fork.c > index ab5211b..54bb88a 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -454,8 +454,8 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) > if (retval) > goto out; > > - if (file && uprobe_mmap(tmp)) > - goto out; > + if (file) > + uprobe_mmap(tmp); > } > /* a new mm has just been created */ > arch_dup_mmap(oldmm, mm); > diff --git a/mm/mmap.c b/mm/mmap.c > index 4fe2697..f25fd3f 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -1355,9 +1355,8 @@ out: > } else if ((flags & MAP_POPULATE) && !(flags & MAP_NONBLOCK)) > make_pages_present(addr, addr + len); > > - if (file && uprobe_mmap(vma)) > - /* matching probes but cannot insert */ > - goto unmap_and_free_vma; > + if (file) > + uprobe_mmap(vma); > > return addr; >