Re: [PATCH v4 1/8] platform/x86: think-lmi: mutex protection around multiple WMI calls

[Hans de Goede]

Hi,

On 6/1/23 22:05, Mark Pearson wrote:
> When an attribute is being changed if the Admin account is enabled, or if a password
> is being updated then multiple WMI calls are needed.
> Add mutex protection to ensure no race conditions are introduced.
> 
> Fixes: b49f72e7f96d ("platform/x86: think-lmi: Certificate authentication support")
> Signed-off-by: Mark Pearson <mpearson-lenovo@xxxxxxxxx>

Thank you for your patch-series, I've applied the series to my
review-hans branch:
https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/log/?h=review-hans

Note it will show up in my review-hans branch once I've pushed my
local branch there, which might take a while.

Once I've run some tests on this branch the patches there will be
added to the platform-drivers-x86/for-next branch and eventually
will be included in the pdx86 pull-request to Linus for the next
merge-window.

Regards,

Hans





> ---
> Changes in v2:
>  - New commit added after review of other patches in series.
> Changes in v3:
>  - Simplified mutex handling as recommended.
> Changes in v4:
>  - This was the 5th patch in the series but moved to be first.
>  - Added Fixes tag.
>  - Improved commit information to be clearer.
> 
>  drivers/platform/x86/think-lmi.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/platform/x86/think-lmi.c b/drivers/platform/x86/think-lmi.c
> index 1138f770149d..6cf77bc26b05 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 */
> @@ -437,6 +439,9 @@ static ssize_t new_password_store(struct kobject *kobj,
>  	/* Strip out CR if one is present, setting password won't work if it is present */
>  	strip_cr(new_pwd);
>  
> +	/* Use lock in case multiple WMI operations needed */
> +	mutex_lock(&tlmi_mutex);
> +
>  	pwdlen = strlen(new_pwd);
>  	/* pwdlen == 0 is allowed to clear the password */
>  	if (pwdlen && ((pwdlen < setting->minlen) || (pwdlen > setting->maxlen))) {
> @@ -493,6 +498,7 @@ static ssize_t new_password_store(struct kobject *kobj,
>  		kfree(auth_str);
>  	}
>  out:
> +	mutex_unlock(&tlmi_mutex);
>  	kfree(new_pwd);
>  	return ret ?: count;
>  }
> @@ -981,6 +987,9 @@ static ssize_t current_value_store(struct kobject *kobj,
>  	/* Strip out CR if one is present */
>  	strip_cr(new_setting);
>  
> +	/* Use lock in case multiple WMI operations needed */
> +	mutex_lock(&tlmi_mutex);
> +
>  	/* Check if certificate authentication is enabled and active */
>  	if (tlmi_priv.certificate_support && tlmi_priv.pwd_admin->cert_installed) {
>  		if (!tlmi_priv.pwd_admin->signature || !tlmi_priv.pwd_admin->save_signature) {
> @@ -1039,6 +1048,7 @@ static ssize_t current_value_store(struct kobject *kobj,
>  		kobject_uevent(&tlmi_priv.class_dev->kobj, KOBJ_CHANGE);
>  	}
>  out:
> +	mutex_unlock(&tlmi_mutex);
>  	kfree(auth_str);
>  	kfree(set_str);
>  	kfree(new_setting);