Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751400Ab1DPD2U (ORCPT ); Fri, 15 Apr 2011 23:28:20 -0400 Received: from smtp-out.google.com ([216.239.44.51]:4716 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750923Ab1DPD2T (ORCPT ); Fri, 15 Apr 2011 23:28:19 -0400 From: Sonny Rao To: Jamie Iles Cc: olofj@chromium.org, Sonny Rao , Peter Zijlstra , Paul Mackerras , Ingo Molnar , Arnaldo Carvalho de Melo , Russell King , Will Deacon , Jamie Iles , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH] Fix infinite loop in ARM user perf_event backtrace code Date: Fri, 15 Apr 2011 20:27:25 -0700 Message-Id: <1302924445-18557-1-git-send-email-sonnyrao@chromium.org> X-Mailer: git-send-email 1.7.3.1 X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1217 Lines: 33 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); } -- 1.7.3.1 -- 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/