From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753140Ab2HSRRN (ORCPT ); Sun, 19 Aug 2012 13:17:13 -0400 Received: from mx1.redhat.com ([209.132.183.28]:61687 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751353Ab2HSRRL (ORCPT ); Sun, 19 Aug 2012 13:17:11 -0400 Date: Sun, 19 Aug 2012 19:13:40 +0200 From: Oleg Nesterov To: Linus Torvalds Cc: Anton Arapov , Ingo Molnar , Srikar Dronamraju , William Cohen , linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/1] uprobes: mmap_region() corrupts mm->mm_rb if uprobe_mmap() fails Message-ID: <20120819171340.GC26957@redhat.com> References: <20120819170917.GA26953@redhat.com> <20120819170937.GA26957@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120819170937.GA26957@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 OOPS, sorry, wrong subject. Ignore this email, see the next one. On 08/19, Oleg Nesterov wrote: > > https://bugzilla.redhat.com/show_bug.cgi?id=843640 > > 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 but this is how > William noticed this bug. > > 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. > > And, if nothing else, both mmap_region() and dup_mmap() return > success if uprobe_mmap() fails. Change them to ignore the error > code from uprobe_mmap(). > > Reported-and-tested-by: William Cohen > Signed-off-by: Oleg Nesterov > Acked-by: Srikar Dronamraju > 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; > > -- > 1.5.5.1 >