From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935257AbaGPTYo (ORCPT ); Wed, 16 Jul 2014 15:24:44 -0400 Received: from terminus.zytor.com ([198.137.202.10]:44581 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932138AbaGPTYf (ORCPT ); Wed, 16 Jul 2014 15:24:35 -0400 Date: Wed, 16 Jul 2014 12:23:18 -0700 From: tip-bot for Jason Baron Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, andi@firstfloor.org, torvalds@linux-foundation.org, peterz@infradead.org, jbaron@akamai.com, tglx@linutronix.de Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, andi@firstfloor.org, torvalds@linux-foundation.org, peterz@infradead.org, jbaron@akamai.com, tglx@linutronix.de In-Reply-To: <9d7780c83db26683955cd01e6bc654ee2586e67f.1404315388.git.jbaron@akamai.com> References: <9d7780c83db26683955cd01e6bc654ee2586e67f.1404315388.git.jbaron@akamai.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched: Fix static_key race with sched_feat() Git-Commit-ID: 5cd08fbfdb6baa9fe98f530b76898fc5725a6289 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: 5cd08fbfdb6baa9fe98f530b76898fc5725a6289 Gitweb: http://git.kernel.org/tip/5cd08fbfdb6baa9fe98f530b76898fc5725a6289 Author: Jason Baron AuthorDate: Wed, 2 Jul 2014 15:52:44 +0000 Committer: Ingo Molnar CommitDate: Wed, 16 Jul 2014 13:38:21 +0200 sched: Fix static_key race with sched_feat() As pointed out by Andi Kleen, the usage of static keys can be racy in sched_feat_disable() vs. sched_feat_enable(). Currently, we first check the value of keys->enabled, and subsequently update the branch direction. This, can be racy and can potentially leave the keys in an inconsistent state. Take the i_mutex around these calls to resolve the race. Reported-by: Andi Kleen Signed-off-by: Jason Baron Signed-off-by: Peter Zijlstra Cc: Linus Torvalds Cc: rostedt@goodmis.org Link: http://lkml.kernel.org/r/9d7780c83db26683955cd01e6bc654ee2586e67f.1404315388.git.jbaron@akamai.com Signed-off-by: Ingo Molnar --- kernel/sched/core.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 2f96081..8705125 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -245,6 +245,7 @@ sched_feat_write(struct file *filp, const char __user *ubuf, char buf[64]; char *cmp; int i; + struct inode *inode; if (cnt > 63) cnt = 63; @@ -255,7 +256,11 @@ sched_feat_write(struct file *filp, const char __user *ubuf, buf[cnt] = 0; cmp = strstrip(buf); + /* Ensure the static_key remains in a consistent state */ + inode = file_inode(filp); + mutex_lock(&inode->i_mutex); i = sched_feat_set(cmp); + mutex_unlock(&inode->i_mutex); if (i == __SCHED_FEAT_NR) return -EINVAL;