From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753380AbbANOCs (ORCPT ); Wed, 14 Jan 2015 09:02:48 -0500 Received: from terminus.zytor.com ([198.137.202.10]:36868 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752785AbbANOCq (ORCPT ); Wed, 14 Jan 2015 09:02:46 -0500 Date: Wed, 14 Jan 2015 06:02:10 -0800 From: tip-bot for Tetsuo Handa Message-ID: Cc: peterz@infradead.org, hpa@zytor.com, mingo@kernel.org, tglx@linutronix.de, linux-kernel@vger.kernel.org, penguin-kernel@I-love.SAKURA.ne.jp, torvalds@linux-foundation.org Reply-To: torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, penguin-kernel@I-love.SAKURA.ne.jp, tglx@linutronix.de, mingo@kernel.org, peterz@infradead.org, hpa@zytor.com In-Reply-To: <201412052131.GCE35924.FVHFOtLOJOMQFS@I-love.SAKURA.ne.jp> References: <201412052131.GCE35924.FVHFOtLOJOMQFS@I-love.SAKURA.ne.jp> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched/debug: Fix potential call to __ffs(0) in sched_show_task() Git-Commit-ID: 1f8a7633094b7886c0677b78ba60b82e501f3ce6 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 1f8a7633094b7886c0677b78ba60b82e501f3ce6 Gitweb: http://git.kernel.org/tip/1f8a7633094b7886c0677b78ba60b82e501f3ce6 Author: Tetsuo Handa AuthorDate: Fri, 5 Dec 2014 21:22:22 +0900 Committer: Ingo Molnar CommitDate: Wed, 14 Jan 2015 13:34:15 +0100 sched/debug: Fix potential call to __ffs(0) in sched_show_task() "struct task_struct"->state is "volatile long" and __ffs() warns that "Undefined if no bit exists, so code should check against 0 first." Therefore, at expression state = p->state ? __ffs(p->state) + 1 : 0; in sched_show_task(), CPU might see "p->state" before "?" as "non-zero" but "p->state" after "?" as "zero", which could result in "state >= sizeof(stat_nam)" being true and bogus '?' is printed. This patch changes "state" from "unsigned int" to "unsigned long" and save "p->state" before calling __ffs(), in order to avoid potential call to __ffs(0). Signed-off-by: Tetsuo Handa Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Link: http://lkml.kernel.org/r/201412052131.GCE35924.FVHFOtLOJOMQFS@I-love.SAKURA.ne.jp Signed-off-by: Ingo Molnar --- kernel/sched/core.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 56c9b79..816c172 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4508,9 +4508,10 @@ void sched_show_task(struct task_struct *p) { unsigned long free = 0; int ppid; - unsigned state; + unsigned long state = p->state; - state = p->state ? __ffs(p->state) + 1 : 0; + if (state) + state = __ffs(state) + 1; printk(KERN_INFO "%-15.15s %c", p->comm, state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?'); #if BITS_PER_LONG == 32