Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754725AbaFNNAp (ORCPT ); Sat, 14 Jun 2014 09:00:45 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36938 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754644AbaFNNAl (ORCPT ); Sat, 14 Jun 2014 09:00:41 -0400 From: Mateusz Guzik To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Peter Zijlstra , stable@vger.kernel.org Subject: [PATCH] sched: fix possible divide by zero in avg_atom calculation Date: Sat, 14 Jun 2014 15:00:09 +0200 Message-Id: <1402750809-31991-1-git-send-email-mguzik@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org proc_sched_show_task does: if (nr_switches) do_div(avg_atom, nr_switches); nr_switches is unsigned long and do_div truncates it to 32 bits, which means it can test non-zero on e.g. x86-64 and be truncated to zero for division. Fix the problem by using div64_ul instead. As a side effect calculations of avg_atom for big nr_switches are now correct. Signed-off-by: Mateusz Guzik Cc: Ingo Molnar Cc: Peter Zijlstra Cc: stable@vger.kernel.org --- kernel/sched/debug.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 695f977..627b3c3 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -608,7 +608,7 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m) avg_atom = p->se.sum_exec_runtime; if (nr_switches) - do_div(avg_atom, nr_switches); + avg_atom = div64_ul(avg_atom, nr_switches); else avg_atom = -1LL; -- 1.8.3.1 -- 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/