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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Odin Ugedal <odin@uged.al>, Peter Zijlstra <peterz@infradead.org>,
	Ben Segall <bsegall@google.com>, Sasha Levin <sashal@kernel.org>
Subject: [PATCH AUTOSEL 4.9 18/18] sched/fair: Fix CFS bandwidth hrtimer expiry type
Date: Wed, 14 Jul 2021 15:48:06 -0400	[thread overview]
Message-ID: <20210714194806.55962-18-sashal@kernel.org> (raw)
In-Reply-To: <20210714194806.55962-1-sashal@kernel.org>

From: Odin Ugedal <odin@uged.al>

[ Upstream commit 72d0ad7cb5bad265adb2014dbe46c4ccb11afaba ]

The time remaining until expiry of the refresh_timer can be negative.
Casting the type to an unsigned 64-bit value will cause integer
underflow, making the runtime_refresh_within return false instead of
true. These situations are rare, but they do happen.

This does not cause user-facing issues or errors; other than
possibly unthrottling cfs_rq's using runtime from the previous period(s),
making the CFS bandwidth enforcement less strict in those (special)
situations.

Signed-off-by: Odin Ugedal <odin@uged.al>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ben Segall <bsegall@google.com>
Link: https://lore.kernel.org/r/20210629121452.18429-1-odin@uged.al
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/sched/fair.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 5a349fcb634e..39b59248d9c3 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4196,7 +4196,7 @@ static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
 {
 	struct hrtimer *refresh_timer = &cfs_b->period_timer;
-	u64 remaining;
+	s64 remaining;
 
 	/* if the call-back is running a quota refresh is already occurring */
 	if (hrtimer_callback_running(refresh_timer))
@@ -4204,7 +4204,7 @@ static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
 
 	/* is a quota refresh about to occur? */
 	remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer));
-	if (remaining < min_expire)
+	if (remaining < (s64)min_expire)
 		return 1;
 
 	return 0;
-- 
2.30.2


      parent reply	other threads:[~2021-07-14 20:03 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-14 19:47 [PATCH AUTOSEL 4.9 01/18] ARM: dts: rockchip: fix pinctrl sleep nodename for rk3036-kylin and rk3288 Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 02/18] ARM: dts: rockchip: Fix power-controller node names for rk3288 Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 03/18] reset: ti-syscon: fix to_ti_syscon_reset_data macro Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 04/18] ARM: brcmstb: dts: fix NAND nodes names Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 05/18] ARM: dts: BCM63xx: Fix " Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 06/18] ARM: dts: imx25-pinfunc: Fix gpio function name for pads GPIO_[A-F] Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 07/18] ARM: dts: imx6: phyFLEX: Fix UART hardware flow control Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 08/18] ARM: imx: pm-imx5: Fix references to imx5_cpu_suspend_info Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 09/18] ARM: dts: am437x: align gpio hog names with dt-schema Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 10/18] ARM: dts: omap5-board-common: " Sasha Levin
2021-07-14 19:47 ` [PATCH AUTOSEL 4.9 11/18] ARM: dts: stm32: fix RCC node name on stm32f429 MCU Sasha Levin
2021-07-14 19:48 ` [PATCH AUTOSEL 4.9 12/18] arm64: dts: juno: Update SCPI nodes as per the YAML schema Sasha Levin
2021-07-14 19:48 ` [PATCH AUTOSEL 4.9 13/18] thermal/core: Correct function name thermal_zone_device_unregister() Sasha Levin
2021-07-14 19:48 ` [PATCH AUTOSEL 4.9 14/18] kbuild: mkcompile_h: consider timestamp if KBUILD_BUILD_TIMESTAMP is set Sasha Levin
2021-07-14 19:48 ` [PATCH AUTOSEL 4.9 15/18] rtc: max77686: Do not enforce (incorrect) interrupt trigger type Sasha Levin
2021-07-14 19:48 ` [PATCH AUTOSEL 4.9 16/18] scsi: aic7xxx: Fix unintentional sign extension issue on left shift of u8 Sasha Levin
2021-07-14 19:48 ` [PATCH AUTOSEL 4.9 17/18] scsi: be2iscsi: Fix some missing space in some messages Sasha Levin
2021-07-16 19:22   ` Marion & Christophe JAILLET
2021-07-21 10:42     ` Sasha Levin
2021-07-14 19:48 ` Sasha Levin [this message]

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