From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 43C3FC65BAF for ; Sun, 9 Dec 2018 22:19:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 090D220661 for ; Sun, 9 Dec 2018 22:19:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 090D220661 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=decadent.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728119AbeLIWTT (ORCPT ); Sun, 9 Dec 2018 17:19:19 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:35594 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726472AbeLIVz1 (ORCPT ); Sun, 9 Dec 2018 16:55:27 -0500 Received: from pub.yeoldevic.com ([81.174.156.145] helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1gW72q-0002ii-G8; Sun, 09 Dec 2018 21:55:24 +0000 Received: from ben by deadeye with local (Exim 4.91) (envelope-from ) id 1gW72l-0003hc-Ru; Sun, 09 Dec 2018 21:55:19 +0000 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Thomas Gleixner" , "Michael Kerrisk" , "Team OWL337" , "Peter Zijlstra" , "John Stultz" Date: Sun, 09 Dec 2018 21:50:33 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 324/328] posix-timers: Sanitize overrun handling In-Reply-To: X-SA-Exim-Connect-IP: 81.174.156.145 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.62-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Gleixner commit 78c9c4dfbf8c04883941445a195276bb4bb92c76 upstream. The posix timer overrun handling is broken because the forwarding functions can return a huge number of overruns which does not fit in an int. As a consequence timer_getoverrun(2) and siginfo::si_overrun can turn into random number generators. The k_clock::timer_forward() callbacks return a 64 bit value now. Make k_itimer::ti_overrun[_last] 64bit as well, so the kernel internal accounting is correct. 3Remove the temporary (int) casts. Add a helper function which clamps the overrun value returned to user space via timer_getoverrun(2) or siginfo::si_overrun limited to a positive value between 0 and INT_MAX. INT_MAX is an indicator for user space that the overrun value has been clamped. Reported-by: Team OWL337 Signed-off-by: Thomas Gleixner Acked-by: John Stultz Cc: Peter Zijlstra Cc: Michael Kerrisk Link: https://lkml.kernel.org/r/20180626132705.018623573@linutronix.de [bwh: Backported to 3.16: adjust filenames, context] Signed-off-by: Ben Hutchings --- include/linux/posix-timers.h | 4 ++-- kernel/posix-cpu-timers.c | 2 +- kernel/posix-timers.c | 31 ++++++++++++++++++++----------- 3 files changed, 23 insertions(+), 14 deletions(-) --- a/include/linux/posix-timers.h +++ b/include/linux/posix-timers.h @@ -65,8 +65,8 @@ struct k_itimer { spinlock_t it_lock; clockid_t it_clock; /* which timer type */ timer_t it_id; /* timer id */ - int it_overrun; /* overrun on pending signal */ - int it_overrun_last; /* overrun on last delivered signal */ + s64 it_overrun; /* overrun on pending signal */ + s64 it_overrun_last; /* overrun on last delivered signal */ int it_requeue_pending; /* waiting to requeue this timer */ #define REQUEUE_PENDING 1 int it_sigev_notify; /* notify word of sigevent struct */ --- a/kernel/posix-cpu-timers.c +++ b/kernel/posix-cpu-timers.c @@ -103,7 +103,7 @@ static void bump_cpu_timer(struct k_itim continue; timer->it.cpu.expires += incr; - timer->it_overrun += 1 << i; + timer->it_overrun += 1LL << i; delta -= incr; } } --- a/kernel/posix-timers.c +++ b/kernel/posix-timers.c @@ -347,6 +347,17 @@ static __init int init_posix_timers(void __initcall(init_posix_timers); +/* + * The siginfo si_overrun field and the return value of timer_getoverrun(2) + * are of type int. Clamp the overrun value to INT_MAX + */ +static inline int timer_overrun_to_int(struct k_itimer *timr, int baseval) +{ + s64 sum = timr->it_overrun_last + (s64)baseval; + + return sum > (s64)INT_MAX ? INT_MAX : (int)sum; +} + static void schedule_next_timer(struct k_itimer *timr) { struct hrtimer *timer = &timr->it.real.timer; @@ -354,12 +365,11 @@ static void schedule_next_timer(struct k if (timr->it.real.interval.tv64 == 0) return; - timr->it_overrun += (unsigned int) hrtimer_forward(timer, - timer->base->get_time(), - timr->it.real.interval); + timr->it_overrun += hrtimer_forward(timer, timer->base->get_time(), + timr->it.real.interval); timr->it_overrun_last = timr->it_overrun; - timr->it_overrun = -1; + timr->it_overrun = -1LL; ++timr->it_requeue_pending; hrtimer_restart(timer); } @@ -388,7 +398,7 @@ void do_schedule_next_timer(struct sigin else schedule_next_timer(timr); - info->si_overrun += timr->it_overrun_last; + info->si_overrun = timer_overrun_to_int(timr, info->si_overrun); } if (timr) @@ -483,9 +493,8 @@ static enum hrtimer_restart posix_timer_ now = ktime_add(now, kj); } #endif - timr->it_overrun += (unsigned int) - hrtimer_forward(timer, now, - timr->it.real.interval); + timr->it_overrun += hrtimer_forward(timer, now, + timr->it.real.interval); ret = HRTIMER_RESTART; ++timr->it_requeue_pending; } @@ -633,7 +642,7 @@ SYSCALL_DEFINE3(timer_create, const cloc it_id_set = IT_ID_SET; new_timer->it_id = (timer_t) new_timer_id; new_timer->it_clock = which_clock; - new_timer->it_overrun = -1; + new_timer->it_overrun = -1LL; if (timer_event_spec) { if (copy_from_user(&event, timer_event_spec, sizeof (event))) { @@ -763,7 +772,7 @@ common_timer_get(struct k_itimer *timr, * expiry is > now. */ if (iv.tv64 && (timr->it_requeue_pending & REQUEUE_PENDING || sig_none)) - timr->it_overrun += (unsigned int) hrtimer_forward(timer, now, iv); + timr->it_overrun += hrtimer_forward(timer, now, iv); remaining = ktime_sub(hrtimer_get_expires(timer), now); /* Return 0 only, when the timer is expired and not pending */ @@ -825,7 +834,7 @@ SYSCALL_DEFINE1(timer_getoverrun, timer_ if (!timr) return -EINVAL; - overrun = timr->it_overrun_last; + overrun = timer_overrun_to_int(timr, 0); unlock_timer(timr, flags); return overrun;