From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932261AbeAHTI5 (ORCPT + 1 other); Mon, 8 Jan 2018 14:08:57 -0500 Received: from circinus.uberspace.de ([95.143.172.228]:41814 "EHLO circinus.uberspace.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932181AbeAHTI4 (ORCPT ); Mon, 8 Jan 2018 14:08:56 -0500 X-Greylist: delayed 401 seconds by postgrey-1.27 at vger.kernel.org; Mon, 08 Jan 2018 14:08:56 EST From: "Max R. P. Grossmann" To: linux-kernel@vger.kernel.org Cc: tglx@linutronix.de, john.stultz@linaro.org, "Max R. P. Grossmann" Subject: [PATCH] time: POSIX CPU timers: Ensure that variable is initialized Date: Mon, 8 Jan 2018 20:01:57 +0100 Message-Id: <20180108190157.10048-1-m@max.pm> X-Mailer: git-send-email 2.15.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: If cpu_timer_sample_group returns -EINVAL, it will not have written into *sample. Checking for cpu_timer_sample_group's return value precludes the potential use of an uninitialized value of now in the following block. Given an invalid clock_idx, the previous code could otherwise overwrite *oldval in an undefined manner. This is now prevented. We also exploit short-circuiting of && to sample the timer only if the result will actually be used to update *oldval. Signed-off-by: Max R. P. Grossmann --- kernel/time/posix-cpu-timers.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index 1f27887aa194..e54638be6e19 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -1189,9 +1189,8 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx, u64 now; WARN_ON_ONCE(clock_idx == CPUCLOCK_SCHED); - cpu_timer_sample_group(clock_idx, tsk, &now); - if (oldval) { + if (oldval && cpu_timer_sample_group(clock_idx, tsk, &now) != -EINVAL) { /* * We are setting itimer. The *oldval is absolute and we update * it to be relative, *newval argument is relative and we update -- 2.15.1