From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932374Ab3B0NPY (ORCPT ); Wed, 27 Feb 2013 08:15:24 -0500 Received: from mx1.redhat.com ([209.132.183.28]:52979 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759904Ab3B0NPX (ORCPT ); Wed, 27 Feb 2013 08:15:23 -0500 Date: Wed, 27 Feb 2013 14:14:56 +0100 From: Jiri Olsa To: Frederic Weisbecker Cc: linux-kernel@vger.kernel.org, Corey Ashford , Ingo Molnar , Namhyung Kim , Paul Mackerras , Peter Zijlstra , Arnaldo Carvalho de Melo Subject: Re: [PATCH] perf: Fix vmalloc ring buffer free function Message-ID: <20130227131456.GD1054@krava.brq.redhat.com> References: <1361892861-11070-1-git-send-email-jolsa@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 27, 2013 at 02:02:39PM +0100, Frederic Weisbecker wrote: > 2013/2/26 Jiri Olsa : > > If we allocate perf ring buffer with the size of single page, > > we will get memory corruption when releasing it. It's caused > > by rb_free_work function (the CONFIG_PERF_USE_VMALLOC option > > variant). > > > > For single page sized ring buffer the page_order is -1 (because > > nr_pages is 0). This needs to be recognized in the rb_free_work > > function and set 'nr' to 0 in this case, so only the user page > > gets freed. > > > > Reported-by: Jan Stancek > > Signed-off-by: Jiri Olsa > > Cc: Corey Ashford > > Cc: Frederic Weisbecker > > Cc: Ingo Molnar > > Cc: Namhyung Kim > > Cc: Paul Mackerras > > Cc: Peter Zijlstra > > Cc: Arnaldo Carvalho de Melo > > --- > > kernel/events/ring_buffer.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c > > index 23cb34f..21159fb 100644 > > --- a/kernel/events/ring_buffer.c > > +++ b/kernel/events/ring_buffer.c > > @@ -336,7 +336,8 @@ static void rb_free_work(struct work_struct *work) > > int i, nr; > > > > rb = container_of(work, struct ring_buffer, work); > > - nr = 1 << page_order(rb); > > + /* -1 if there's only user page */ > > + nr = page_order(rb) == -1 ? 0 : 1 << page_order(rb); > > So we allow for 0 sized ring buffer? I'm not entirely convinced this > is a good idea. Besides this above case, perf_output_begin() looks We actually have test perf case 'tools/perf/tests/rdpmc.c' using just the user page for counter id and other stuff.. > dangerous in the case of CONFIG_PERF_USE_VMALLOC due to page_order() > being -1. At least rb->nr_pages sould be zero in that case. right, seems to suffer the same way as rb_free_work.. will check thanks, jirka