Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932716Ab0GAUxM (ORCPT ); Thu, 1 Jul 2010 16:53:12 -0400 Received: from kroah.org ([198.145.64.141]:47831 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932819Ab0GAUvJ (ORCPT ); Thu, 1 Jul 2010 16:51:09 -0400 X-Mailbox-Line: From gregkh@clark.site Thu Jul 1 10:34:37 2010 Message-Id: <20100701173437.339606380@clark.site> User-Agent: quilt/0.48-10.1 Date: Thu, 01 Jul 2010 10:35:11 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Peter Zijlstra , Ingo Molnar Subject: [patch 125/164] perf: Fix signed comparison in perf_adjust_period() In-Reply-To: <20100701175152.GA2135@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1853 Lines: 59 2.6.33-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Zijlstra commit f6ab91add6355e231e1c47897027b2a6ee4fa268 upstream. Frederic reported that frequency driven swevents didn't work properly and even caused a division-by-zero error. It turns out there are two bugs, the division-by-zero comes from a failure to deal with that in perf_calculate_period(). The other was more interesting and turned out to be a wrong comparison in perf_adjust_period(). The comparison was between an s64 and u64 and got implicitly converted to an unsigned comparison. The problem is that period_left is typically < 0, so it ended up being always true. Cure this by making the local period variables s64. Reported-by: Frederic Weisbecker Tested-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra LKML-Reference: Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- kernel/perf_event.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -1417,13 +1417,16 @@ do { \ divisor = nsec * frequency; } + if (!divisor) + return dividend; + return div64_u64(dividend, divisor); } static void perf_adjust_period(struct perf_event *event, u64 nsec, u64 count) { struct hw_perf_event *hwc = &event->hw; - u64 period, sample_period; + s64 period, sample_period; s64 delta; period = perf_calculate_period(event, nsec, count); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/