Re: [PATCH 5/5] platform/x86: think-lmi: mutex protection around multiple WMI calls

[Hans de Goede <hdegoede@redhat.com>]

Hi Mark,

On 5/25/23 21:31, Mark Pearson wrote:
> Add mutex protection around cases where an operation needs multiple
> WMI calls - e.g. setting password.
> 
> Signed-off-by: Mark Pearson <mpearson-lenovo@squebb.ca>
> ---
> Changes in V2: New commit added after review of other patches in series.
> 
>  drivers/platform/x86/think-lmi.c | 46 ++++++++++++++++++++++++--------
>  1 file changed, 35 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/platform/x86/think-lmi.c b/drivers/platform/x86/think-lmi.c
> index 64cd453d6e7d..f3e1e4dacba2 100644
> --- a/drivers/platform/x86/think-lmi.c
> +++ b/drivers/platform/x86/think-lmi.c
> @@ -14,6 +14,7 @@
>  #include <linux/acpi.h>
>  #include <linux/errno.h>
>  #include <linux/fs.h>
> +#include <linux/mutex.h>
>  #include <linux/string.h>
>  #include <linux/types.h>
>  #include <linux/dmi.h>
> @@ -195,6 +196,7 @@ static const char * const level_options[] = {
>  };
>  static struct think_lmi tlmi_priv;
>  static struct class *fw_attr_class;
> +static DEFINE_MUTEX(tlmi_mutex);
>  
>  /* ------ Utility functions ------------*/
>  /* Strip out CR if one is present */
> @@ -463,23 +465,32 @@ static ssize_t new_password_store(struct kobject *kobj,
>  			sprintf(pwd_type, "%s", setting->pwd_type);
>  		}
>  
> +		mutex_lock(&tlmi_mutex);
>  		ret = tlmi_opcode_setting("WmiOpcodePasswordType", pwd_type);
> -		if (ret)
> +		if (ret) {
> +			mutex_unlock(&tlmi_mutex);
>  			goto out;
> -
> +		}
>  		if (tlmi_priv.pwd_admin->valid) {
>  			ret = tlmi_opcode_setting("WmiOpcodePasswordAdmin",
>  					tlmi_priv.pwd_admin->password);
> -			if (ret)
> +			if (ret) {
> +				mutex_unlock(&tlmi_mutex);
>  				goto out;
> +			}
>  		}
>  		ret = tlmi_opcode_setting("WmiOpcodePasswordCurrent01", setting->password);
> -		if (ret)
> +		if (ret) {
> +			mutex_unlock(&tlmi_mutex);
>  			goto out;
> +		}
>  		ret = tlmi_opcode_setting("WmiOpcodePasswordNew01", new_pwd);
> -		if (ret)
> +		if (ret) {
> +			mutex_unlock(&tlmi_mutex);
>  			goto out;
> +		}
>  		ret = tlmi_simple_call(LENOVO_OPCODE_IF_GUID, "WmiOpcodePasswordSetUpdate;");
> +		mutex_unlock(&tlmi_mutex);
>  	} else {
>  		/* Format: 'PasswordType,CurrentPw,NewPw,Encoding,KbdLang;' */
>  		auth_str = kasprintf(GFP_KERNEL, "%s,%s,%s,%s,%s;",


I haven't take a really close / good look yet. But at a first glance
I think it would be cleaner to just take the mutex at the top
and unlock it after the out label to which all the existing goto-s
already go ?

> @@ -1000,11 +1011,16 @@ static ssize_t current_value_store(struct kobject *kobj,
>  			goto out;
>  		}
>  
> +		mutex_lock(&tlmi_mutex);
>  		ret = tlmi_simple_call(LENOVO_SET_BIOS_SETTING_CERT_GUID, set_str);
> -		if (ret)
> +		if (ret) {
> +			mutex_unlock(&tlmi_mutex);
>  			goto out;
> +		}
>  		ret = tlmi_simple_call(LENOVO_SAVE_BIOS_SETTING_CERT_GUID,
>  				tlmi_priv.pwd_admin->save_signature);
> +
> +		mutex_unlock(&tlmi_mutex);
>  		if (ret)
>  			goto out;
>  	} else if (tlmi_priv.opcode_support) {
> @@ -1021,18 +1037,23 @@ static ssize_t current_value_store(struct kobject *kobj,
>  			goto out;
>  		}
>  
> +		mutex_lock(&tlmi_mutex);
>  		ret = tlmi_simple_call(LENOVO_SET_BIOS_SETTINGS_GUID, set_str);
> -		if (ret)
> +		if (ret) {
> +			mutex_unlock(&tlmi_mutex);
>  			goto out;
> +		}
>  
>  		if (tlmi_priv.pwd_admin->valid && tlmi_priv.pwd_admin->password[0]) {
>  			ret = tlmi_opcode_setting("WmiOpcodePasswordAdmin",
>  					tlmi_priv.pwd_admin->password);
> -			if (ret)
> +			if (ret) {
> +				mutex_unlock(&tlmi_mutex);
>  				goto out;
> +			}
>  		}
> -
>  		ret = tlmi_save_bios_settings("");
> +		mutex_unlock(&tlmi_mutex);
>  	} else { /* old non opcode based authentication method (deprecated)*/
>  		if (tlmi_priv.pwd_admin->valid && tlmi_priv.pwd_admin->password[0]) {
>  			auth_str = kasprintf(GFP_KERNEL, "%s,%s,%s;",
> @@ -1056,14 +1077,17 @@ static ssize_t current_value_store(struct kobject *kobj,
>  			goto out;
>  		}
>  
> +		mutex_lock(&tlmi_mutex);
>  		ret = tlmi_simple_call(LENOVO_SET_BIOS_SETTINGS_GUID, set_str);
> -		if (ret)
> +		if (ret) {
> +			mutex_unlock(&tlmi_mutex);
>  			goto out;
> -
> +		}
>  		if (auth_str)
>  			ret = tlmi_save_bios_settings(auth_str);
>  		else
>  			ret = tlmi_save_bios_settings("");
> +		mutex_unlock(&tlmi_mutex);
>  	}
>  	if (!ret && !tlmi_priv.pending_changes) {
>  		tlmi_priv.pending_changes = true;

And the same here.

Regards,

Hans