linux-kernel - Re: [PATCH 1/2] clocksource: imx-tpm: fix return -ETIME when delta exceeds INT

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Message-ID: <ZrzfoQdm7MzQlFX4@lizhi-Precision-Tower-5810>
Date: Wed, 14 Aug 2024 12:47:29 -0400
From: Frank Li <Frank.li@....com>
To: Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Dong Aisheng <aisheng.dong@....com>,
	"open list:CLOCKSOURCE, CLOCKEVENT DRIVERS" <linux-kernel@...r.kernel.org>,
	"open list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" <imx@...ts.linux.dev>,
	"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/2] clocksource: imx-tpm: fix return -ETIME when delta
 exceeds INT_MAX

On Thu, Jul 25, 2024 at 03:33:54PM -0400, Frank Li wrote:
> From: Jacky Bai <ping.bai@....com>
>
> In tpm_set_next_event(delta), return -ETIME by wrong cast to int when delta
> is larger than INT_MAX.
>
> For example:
>
> tpm_set_next_event(delta = 0xffff_fffe)
> {
>         ...
>         next = tpm_read_counter(); // assume next is 0x10
>         next += delta; // next will 0xffff_fffe + 0x10 = 0x1_0000_000e
>         now = tpm_read_counter();  // now is 0x10
>         ...
>
>         return (int)(next - now) <= 0 ? -ETIME : 0;
>                      ^^^^^^^^^^
>                      0x1_0000_000e - 0x10 = 0xffff_fffe, which is -2 when
>                      cast to int. So return -ETIME.
> }
>
> To fix this, introduce a 'prev' variable and check if 'now - prev' is
> larger than delta.
>
> Cc: <stable@...r.kernel.org>
> Fixes: 059ab7b82eec ("clocksource/drivers/imx-tpm: Add imx tpm timer support")
> Signed-off-by: Jacky Bai <ping.bai@....com>
> Reviewed-by: Peng Fan <peng.fan@....com>
> Reviewed-by: Ye Li <ye.li@....com>
> Reviewed-by: Jason Liu <jason.hui.liu@....com>
> Signed-off-by: Frank Li <Frank.Li@....com>
> ---

Ping?


>  drivers/clocksource/timer-imx-tpm.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/clocksource/timer-imx-tpm.c b/drivers/clocksource/timer-imx-tpm.c
> index bd64a8a8427f3..cd23caf1e5999 100644
> --- a/drivers/clocksource/timer-imx-tpm.c
> +++ b/drivers/clocksource/timer-imx-tpm.c
> @@ -83,10 +83,10 @@ static u64 notrace tpm_read_sched_clock(void)
>  static int tpm_set_next_event(unsigned long delta,
>  				struct clock_event_device *evt)
>  {
> -	unsigned long next, now;
> +	unsigned long next, prev, now;
>
> -	next = tpm_read_counter();
> -	next += delta;
> +	prev = tpm_read_counter();
> +	next = prev + delta;
>  	writel(next, timer_base + TPM_C0V);
>  	now = tpm_read_counter();
>
> @@ -96,7 +96,7 @@ static int tpm_set_next_event(unsigned long delta,
>  	 * of writing CNT registers which may cause the min_delta event got
>  	 * missed, so we need add a ETIME check here in case it happened.
>  	 */
> -	return (int)(next - now) <= 0 ? -ETIME : 0;
> +	return (now - prev) >= delta ? -ETIME : 0;
>  }
>
>  static int tpm_set_state_oneshot(struct clock_event_device *evt)
> --
> 2.34.1
>