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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 AE780C43381 for ; Wed, 6 Mar 2019 01:29:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 79DA920675 for ; Wed, 6 Mar 2019 01:29:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728473AbfCFB3j (ORCPT ); Tue, 5 Mar 2019 20:29:39 -0500 Received: from szxga05-in.huawei.com ([45.249.212.191]:4772 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726210AbfCFB3i (ORCPT ); Tue, 5 Mar 2019 20:29:38 -0500 Received: from DGGEMS404-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id C0B61644CA90D1FDDBBC; Wed, 6 Mar 2019 09:29:36 +0800 (CST) Received: from linux-ibm.site (10.175.102.37) by DGGEMS404-HUB.china.huawei.com (10.3.19.204) with Microsoft SMTP Server id 14.3.408.0; Wed, 6 Mar 2019 09:29:26 +0800 From: Xiongfeng Wang To: , , CC: , Subject: [RFC PATCH] ntp: Avoid undefined behaviour in second_overflow() Date: Wed, 6 Mar 2019 09:28:30 +0800 Message-ID: <1551835710-53773-1-git-send-email-wangxiongfeng2@huawei.com> X-Mailer: git-send-email 1.7.12.4 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.175.102.37] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When I ran Syzkaller testsuite, I got the following call trace. ================================================================================ UBSAN: Undefined behaviour in kernel/time/ntp.c:457:16 signed integer overflow: 9223372036854775807 + 500 cannot be represented in type 'long int' CPU: 3 PID: 0 Comm: swapper/3 Not tainted 4.19.25-dirty #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0xca/0x13e lib/dump_stack.c:113 ubsan_epilogue+0xe/0x81 lib/ubsan.c:159 handle_overflow+0x193/0x1e2 lib/ubsan.c:190 second_overflow+0x403/0x540 kernel/time/ntp.c:457 accumulate_nsecs_to_secs kernel/time/timekeeping.c:2002 [inline] logarithmic_accumulation kernel/time/timekeeping.c:2046 [inline] timekeeping_advance+0x2bb/0xec0 kernel/time/timekeeping.c:2114 tick_do_update_jiffies64.part.2+0x1a0/0x350 kernel/time/tick-sched.c:97 tick_do_update_jiffies64 kernel/time/tick-sched.c:1229 [inline] tick_nohz_update_jiffies kernel/time/tick-sched.c:499 [inline] tick_nohz_irq_enter kernel/time/tick-sched.c:1232 [inline] tick_irq_enter+0x1fd/0x240 kernel/time/tick-sched.c:1249 irq_enter+0xc4/0x100 kernel/softirq.c:353 entering_irq arch/x86/include/asm/apic.h:517 [inline] entering_ack_irq arch/x86/include/asm/apic.h:523 [inline] smp_apic_timer_interrupt+0x20/0x480 arch/x86/kernel/apic/apic.c:1052 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:864 RIP: 0010:native_safe_halt+0x2/0x10 arch/x86/include/asm/irqflags.h:58 Code: 01 f0 0f 82 bc fd ff ff 48 c7 c7 c0 21 b1 83 e8 a1 0a 02 ff e9 ab fd ff ff 4c 89 e7 e8 77 b6 a5 fe e9 6a ff ff ff 90 90 fb f4 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 f4 c3 90 90 90 90 90 90 RSP: 0018:ffff888106307d20 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13 RAX: 0000000000000007 RBX: dffffc0000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8881062e4f1c RBP: 0000000000000003 R08: ffffed107c5dc77b R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff848c78a0 R13: 0000000000000003 R14: 1ffff11020c60fae R15: 0000000000000000 arch_safe_halt arch/x86/include/asm/paravirt.h:94 [inline] default_idle+0x24/0x2b0 arch/x86/kernel/process.c:561 cpuidle_idle_call kernel/sched/idle.c:153 [inline] do_idle+0x2ca/0x420 kernel/sched/idle.c:262 cpu_startup_entry+0xcb/0xe0 kernel/sched/idle.c:368 start_secondary+0x421/0x570 arch/x86/kernel/smpboot.c:271 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243 ================================================================================ It is because time_maxerror is set as 0x7FFFFFFFFFFFFFFF by user. It overflows when we add it with 'MAXFREQ / NSEC_PER_USEC' in 'second_overflow()'. This patch add a limit check and saturate it when the user set 'time_maxerror'. Signed-off-by: Xiongfeng Wang --- kernel/time/ntp.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c index 36a2bef..38e1b65 100644 --- a/kernel/time/ntp.c +++ b/kernel/time/ntp.c @@ -677,6 +677,8 @@ static inline void process_adjtimex_modes(const struct timex *txc, s32 *time_tai if (txc->modes & ADJ_MAXERROR) time_maxerror = txc->maxerror; + if (time_maxerror > NTP_PHASE_LIMIT) + time_maxerror = NTP_PHASE_LIMIT; if (txc->modes & ADJ_ESTERROR) time_esterror = txc->esterror; -- 1.7.12.4