linux-kernel - Re: [PATCH] alarmtimer: ensure RTC module is not unloaded

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Date:   Mon, 21 Aug 2017 11:42:31 +0200
From:   Michal Simek <monstr@...str.eu>
To:     Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        John Stultz <john.stultz@...aro.org>
Cc:     Stephen Boyd <sboyd@...eaurora.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] alarmtimer: ensure RTC module is not unloaded

On 21.8.2017 00:01, Alexandre Belloni wrote:
> When registering the rtc device to be used to handle alarm timers,
> get_device is used to ensure the device doesn't go away but the module can
> still be unloaded. Call try_module_get to ensure the rtc driver will not go
> away.
> 
> Reported-by: Michal Simek <monstr@...str.eu>
> Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
> ---
>  kernel/time/alarmtimer.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
> index 0b8ff7d257ea..1c682eef7e6b 100644
> --- a/kernel/time/alarmtimer.c
> +++ b/kernel/time/alarmtimer.c
> @@ -28,6 +28,7 @@
>  #include <linux/workqueue.h>
>  #include <linux/freezer.h>
>  #include <linux/compat.h>
> +#include <linux/module.h>
>  
>  #include "posix-timers.h"
>  
> @@ -100,6 +101,11 @@ static int alarmtimer_rtc_add_device(struct device *dev,
>  
>  	spin_lock_irqsave(&rtcdev_lock, flags);
>  	if (!rtcdev) {
> +		if (!try_module_get(rtc->owner)) {
> +			spin_unlock_irqrestore(&rtcdev_lock, flags);
> +			return -1;
> +		}
> +
>  		rtcdev = rtc;
>  		/* hold a reference so it doesn't go away */
>  		get_device(dev);
> 

Tested-by: Michal Simek <michal.simek@...inx.com>

Thanks,
Michal


-- 
Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel - Xilinx Microblaze
Maintainer of Linux kernel - Xilinx Zynq ARM and ZynqMP ARM64 SoCs
U-Boot custodian - Xilinx Microblaze/Zynq/ZynqMP SoCs




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