From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752623AbaG1I3T (ORCPT ); Mon, 28 Jul 2014 04:29:19 -0400 Received: from terminus.zytor.com ([198.137.202.10]:42794 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751170AbaG1I3O (ORCPT ); Mon, 28 Jul 2014 04:29:14 -0400 Date: Mon, 28 Jul 2014 01:28:10 -0700 From: tip-bot for Daniel Bristot de Oliveira Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, torvalds@linux-foundation.org, peterz@infradead.org, bristot@redhat.com, rostedt@goodmis.org, tglx@linutronix.de Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, peterz@infradead.org, bristot@redhat.com, rostedt@goodmis.org, tglx@linutronix.de In-Reply-To: <9ebe0566a08dbbb3999759d3f20d6004bb2dbcfa.1406079891.git.bristot@redhat.com> References: <9ebe0566a08dbbb3999759d3f20d6004bb2dbcfa.1406079891.git.bristot@redhat.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched: Fix sched_setparam() policy == -1 logic Git-Commit-ID: d8d28c8f00e84a72e8bee39a85835635417bee49 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: d8d28c8f00e84a72e8bee39a85835635417bee49 Gitweb: http://git.kernel.org/tip/d8d28c8f00e84a72e8bee39a85835635417bee49 Author: Daniel Bristot de Oliveira AuthorDate: Tue, 22 Jul 2014 23:27:41 -0300 Committer: Ingo Molnar CommitDate: Mon, 28 Jul 2014 10:00:08 +0200 sched: Fix sched_setparam() policy == -1 logic The scheduler uses policy == -1 to preserve the current policy state to implement sched_setparam(). But, as (int) -1 is equals to 0xffffffff, it's matching the if (policy & SCHED_RESET_ON_FORK) on _sched_setscheduler(). This match changes the policy value to an invalid value, breaking the sched_setparam() syscall. This patch checks policy == -1 before check the SCHED_RESET_ON_FORK flag. The following program shows the bug: int main(void) { struct sched_param param = { .sched_priority = 5, }; sched_setscheduler(0, SCHED_FIFO, ¶m); param.sched_priority = 1; sched_setparam(0, ¶m); param.sched_priority = 0; sched_getparam(0, ¶m); if (param.sched_priority != 1) printf("failed priority setting (found %d instead of 1)\n", param.sched_priority); else printf("priority setting fine\n"); } Signed-off-by: Daniel Bristot de Oliveira Signed-off-by: Peter Zijlstra Reviewed-by: Steven Rostedt Cc: # 3.14+ Cc: Linus Torvalds Cc: linux-kernel@vger.kernel.org Fixes: 7479f3c9cf67 "sched: Move SCHED_RESET_ON_FORK into attr::sched_flags" Link: http://lkml.kernel.org/r/9ebe0566a08dbbb3999759d3f20d6004bb2dbcfa.1406079891.git.bristot@redhat.com 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 bc1638b..0acf96b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3558,9 +3558,10 @@ static int _sched_setscheduler(struct task_struct *p, int policy, }; /* - * Fixup the legacy SCHED_RESET_ON_FORK hack + * Fixup the legacy SCHED_RESET_ON_FORK hack, except if + * the policy=-1 was passed by sched_setparam(). */ - if (policy & SCHED_RESET_ON_FORK) { + if ((policy != -1) && (policy & SCHED_RESET_ON_FORK)) { attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK; policy &= ~SCHED_RESET_ON_FORK; attr.sched_policy = policy;