From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-by2nam03on0132.outbound.protection.outlook.com ([104.47.42.132]:16151 "EHLO NAM03-BY2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1032066AbeCAPa2 (ORCPT ); Thu, 1 Mar 2018 10:30:28 -0500 From: Sasha Levin To: "stable@vger.kernel.org" , "stable-commits@vger.kernel.org" CC: Vegard Nossum , John Stultz , Sasha Levin Subject: [added to the 4.1 stable tree] time: Avoid undefined behaviour in ktime_add_safe() Date: Thu, 1 Mar 2018 15:24:39 +0000 Message-ID: <20180301152116.1486-209-alexander.levin@microsoft.com> References: <20180301152116.1486-1-alexander.levin@microsoft.com> In-Reply-To: <20180301152116.1486-1-alexander.levin@microsoft.com> Content-Language: en-US Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org List-ID: From: Vegard Nossum This patch has been added to the 4.1 stable tree. If you have any objections, please let us know. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D [ Upstream commit 979515c5645830465739254abc1b1648ada41518 ] I ran into this: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D UBSAN: Undefined behaviour in kernel/time/hrtimer.c:310:16 signed integer overflow: 9223372036854775807 + 50000 cannot be represented in type 'long long in= t' CPU: 2 PID: 4798 Comm: trinity-c2 Not tainted 4.8.0-rc1+ #91 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.3-0= -ge2fc41e-prebuilt.qemu-project.org 04/01/2014 0000000000000000 ffff88010ce6fb88 ffffffff82344740 0000000041b58ab3 ffffffff84f97a20 ffffffff82344694 ffff88010ce6fbb0 ffff88010ce6fb60 000000000000c350 ffff88010ce6f968 dffffc0000000000 ffffffff857bc320 Call Trace: [] dump_stack+0xac/0xfc [] ? _atomic_dec_and_lock+0xc4/0xc4 [] ubsan_epilogue+0xd/0x8a [] handle_overflow+0x202/0x23d [] ? val_to_string.constprop.6+0x11e/0x11e [] ? timerqueue_add+0x151/0x410 [] ? hrtimer_start_range_ns+0x3b8/0x1380 [] ? memset+0x31/0x40 [] __ubsan_handle_add_overflow+0xe/0x10 [] hrtimer_nanosleep+0x5d9/0x790 [] ? hrtimer_init_sleeper+0x80/0x80 [] ? __might_sleep+0x5b/0x260 [] common_nsleep+0x20/0x30 [] SyS_clock_nanosleep+0x197/0x210 [] ? SyS_clock_getres+0x150/0x150 [] ? __this_cpu_preempt_check+0x13/0x20 [] ? __context_tracking_exit.part.3+0x30/0x1b0 [] ? SyS_clock_getres+0x150/0x150 [] do_syscall_64+0x1b3/0x4b0 [] entry_SYSCALL64_slow_path+0x25/0x25 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D Add a new ktime_add_unsafe() helper which doesn't check for overflow, but doesn't throw a UBSAN warning when it does overflow either. Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Richard Cochran Cc: Prarit Bhargava Signed-off-by: Vegard Nossum Signed-off-by: John Stultz Signed-off-by: Sasha Levin --- include/linux/ktime.h | 7 +++++++ kernel/time/hrtimer.c | 2 +- 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/include/linux/ktime.h b/include/linux/ktime.h index 2b6a204bd8d4..3ffc69ebe967 100644 --- a/include/linux/ktime.h +++ b/include/linux/ktime.h @@ -63,6 +63,13 @@ static inline ktime_t ktime_set(const s64 secs, const un= signed long nsecs) #define ktime_add(lhs, rhs) \ ({ (ktime_t){ .tv64 =3D (lhs).tv64 + (rhs).tv64 }; }) =20 +/* + * Same as ktime_add(), but avoids undefined behaviour on overflow; howeve= r, + * this means that you must check the result for overflow yourself. + */ +#define ktime_add_unsafe(lhs, rhs) \ + ({ (ktime_t){ .tv64 =3D (u64) (lhs).tv64 + (rhs).tv64 }; }) + /* * Add a ktime_t variable and a scalar nanosecond value. * res =3D kt + nsval: diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index 93ef7190bdea..e82a5f40a0ac 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -292,7 +292,7 @@ EXPORT_SYMBOL_GPL(__ktime_divns); */ ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs) { - ktime_t res =3D ktime_add(lhs, rhs); + ktime_t res =3D ktime_add_unsafe(lhs, rhs); =20 /* * We use KTIME_SEC_MAX here, the maximum timeout which we can --=20 2.14.1