linux-kernel - Re: [PATCH v14 01/10] power: reset: reboot-mode: Synchronize list traversal

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Message-ID: <7eqa3rs3nvy7htvrkwyh5m7ok34n6c3h2dxn7xm2abdjzav4hp@i275ed4owgru>
Date: Tue, 16 Sep 2025 20:44:15 +0200
From: Sebastian Reichel <sebastian.reichel@...labora.com>
To: Shivendra Pratap <shivendra.pratap@....qualcomm.com>
Cc: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>, 
	Bjorn Andersson <andersson@...nel.org>, Rob Herring <robh@...nel.org>, 
	Sudeep Holla <sudeep.holla@....com>, Souvik Chakravarty <Souvik.Chakravarty@....com>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Andy Yan <andy.yan@...k-chips.com>, Mark Rutland <mark.rutland@....com>, 
	Lorenzo Pieralisi <lpieralisi@...nel.org>, Arnd Bergmann <arnd@...db.de>, 
	Konrad Dybcio <konradybcio@...nel.org>, cros-qcom-dts-watchers@...omium.org, 
	Vinod Koul <vkoul@...nel.org>, Catalin Marinas <catalin.marinas@....com>, 
	Will Deacon <will@...nel.org>, Florian Fainelli <florian.fainelli@...adcom.com>, 
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>, Mukesh Ojha <mukesh.ojha@....qualcomm.com>, 
	Stephen Boyd <swboyd@...omium.org>, Andre Draszik <andre.draszik@...aro.org>, 
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-arm-msm@...r.kernel.org, 
	Elliot Berman <quic_eberman@...cinc.com>, Srinivas Kandagatla <srini@...nel.org>
Subject: Re: [PATCH v14 01/10] power: reset: reboot-mode: Synchronize list
 traversal

Hi,

On Fri, Aug 15, 2025 at 08:05:06PM +0530, Shivendra Pratap wrote:
> List traversals must be synchronized to prevent race conditions
> and data corruption. The reboot-mode list is not protected by a
> lock currently, which can lead to concurrent access and race.
> 
> Introduce a mutex lock to guard all operations on the reboot-mode
> list and ensure thread-safe access. The change prevents unsafe
> concurrent access on reboot-mode list.
> 
> Signed-off-by: Shivendra Pratap <shivendra.pratap@....qualcomm.com>
> ---

This should use scoped_guard() and a Fixes: tag. Otherwise LGTM.

Greetings,

-- Sebastian

>  drivers/power/reset/reboot-mode.c | 24 ++++++++++++++++++++----
>  include/linux/reboot-mode.h       |  4 ++++
>  2 files changed, 24 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/power/reset/reboot-mode.c b/drivers/power/reset/reboot-mode.c
> index fba53f638da04655e756b5f8b7d2d666d1379535..42bb99128ed3846d4bff62416dc31135ddeaeb90 100644
> --- a/drivers/power/reset/reboot-mode.c
> +++ b/drivers/power/reset/reboot-mode.c
> @@ -29,9 +29,14 @@ static unsigned int get_reboot_mode_magic(struct reboot_mode_driver *reboot,
>  	if (!cmd)
>  		cmd = normal;
>  
> -	list_for_each_entry(info, &reboot->head, list)
> -		if (!strcmp(info->mode, cmd))
> +	mutex_lock(&reboot->rb_lock);
> +	list_for_each_entry(info, &reboot->head, list) {
> +		if (!strcmp(info->mode, cmd)) {
> +			mutex_unlock(&reboot->rb_lock);
>  			return info->magic;
> +		}
> +	}
> +	mutex_unlock(&reboot->rb_lock);
>  
>  	/* try to match again, replacing characters impossible in DT */
>  	if (strscpy(cmd_, cmd, sizeof(cmd_)) == -E2BIG)
> @@ -41,9 +46,14 @@ static unsigned int get_reboot_mode_magic(struct reboot_mode_driver *reboot,
>  	strreplace(cmd_, ',', '-');
>  	strreplace(cmd_, '/', '-');
>  
> -	list_for_each_entry(info, &reboot->head, list)
> -		if (!strcmp(info->mode, cmd_))
> +	mutex_lock(&reboot->rb_lock);
> +	list_for_each_entry(info, &reboot->head, list) {
> +		if (!strcmp(info->mode, cmd_)) {
> +			mutex_unlock(&reboot->rb_lock);
>  			return info->magic;
> +		}
> +	}
> +	mutex_unlock(&reboot->rb_lock);
>  
>  	return 0;
>  }
> @@ -77,7 +87,9 @@ int reboot_mode_register(struct reboot_mode_driver *reboot)
>  	int ret;
>  
>  	INIT_LIST_HEAD(&reboot->head);
> +	mutex_init(&reboot->rb_lock);
>  
> +	mutex_lock(&reboot->rb_lock);
>  	for_each_property_of_node(np, prop) {
>  		if (strncmp(prop->name, PREFIX, len))
>  			continue;
> @@ -113,12 +125,14 @@ int reboot_mode_register(struct reboot_mode_driver *reboot)
>  	reboot->reboot_notifier.notifier_call = reboot_mode_notify;
>  	register_reboot_notifier(&reboot->reboot_notifier);
>  
> +	mutex_unlock(&reboot->rb_lock);
>  	return 0;
>  
>  error:
>  	list_for_each_entry(info, &reboot->head, list)
>  		kfree_const(info->mode);
>  
> +	mutex_unlock(&reboot->rb_lock);
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(reboot_mode_register);
> @@ -133,8 +147,10 @@ int reboot_mode_unregister(struct reboot_mode_driver *reboot)
>  
>  	unregister_reboot_notifier(&reboot->reboot_notifier);
>  
> +	mutex_lock(&reboot->rb_lock);
>  	list_for_each_entry(info, &reboot->head, list)
>  		kfree_const(info->mode);
> +	mutex_unlock(&reboot->rb_lock);
>  
>  	return 0;
>  }
> diff --git a/include/linux/reboot-mode.h b/include/linux/reboot-mode.h
> index 4a2abb38d1d612ec0fdf05eb18c98b210f631b7f..b73f80708197677db8dc2e43affc519782b7146e 100644
> --- a/include/linux/reboot-mode.h
> +++ b/include/linux/reboot-mode.h
> @@ -2,11 +2,15 @@
>  #ifndef __REBOOT_MODE_H__
>  #define __REBOOT_MODE_H__
>  
> +#include <linux/mutex.h>
> +
>  struct reboot_mode_driver {
>  	struct device *dev;
>  	struct list_head head;
>  	int (*write)(struct reboot_mode_driver *reboot, unsigned int magic);
>  	struct notifier_block reboot_notifier;
> +	/*Protects access to reboot mode list*/
> +	struct mutex rb_lock;
>  };
>  
>  int reboot_mode_register(struct reboot_mode_driver *reboot);
> 
> -- 
> 2.34.1
> 
> 

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