Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756187Ab1DRRoL (ORCPT ); Mon, 18 Apr 2011 13:44:11 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:51064 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756080Ab1DRRoD (ORCPT ); Mon, 18 Apr 2011 13:44:03 -0400 Subject: Re: [PATCH] Fix infinite loop in ARM user perf_event backtrace code From: Will Deacon To: Sonny Rao Cc: Jamie Iles , olofj@chromium.org, Peter Zijlstra , Paul Mackerras , Ingo Molnar , Arnaldo Carvalho de Melo , Russell King , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org In-Reply-To: <1302924445-18557-1-git-send-email-sonnyrao@chromium.org> References: <1302924445-18557-1-git-send-email-sonnyrao@chromium.org> Content-Type: text/plain; charset="UTF-8" Date: Mon, 18 Apr 2011 18:42:24 +0100 Message-ID: <1303148544.13157.1.camel@e102144-lin.cambridge.arm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1413 Lines: 37 Hi Sonny, On Sat, 2011-04-16 at 04:27 +0100, Sonny Rao wrote: > The ARM user backtrace code can get into an infinite loop if it > runs into an invalid stack frame which points back to itself. > This situation has been observed in practice. Fix it by capping > the number of entries in the backtrace. This is also what other > architectures do in their backtrace code. > > Signed-off-by: Sonny Rao > --- > arch/arm/kernel/perf_event.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c > index 69cfee0..1e61d60 100644 > --- a/arch/arm/kernel/perf_event.c > +++ b/arch/arm/kernel/perf_event.c > @@ -746,7 +746,8 @@ perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs) > > tail = (struct frame_tail __user *)regs->ARM_fp - 1; > > - while (tail && !((unsigned long)tail & 0x3)) > + while ((entry->nr < PERF_MAX_STACK_DEPTH) && > + tail && !((unsigned long)tail & 0x3)) > tail = user_backtrace(tail, entry); > } Ok. Please can you put this into Russell's patch system? Will -- 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/