Re: [PATCH 1/2] platform/x86: think-lmi: add missing type attribute

From: "Thomas Weißschuh" <thomas@t-8ch.de>
To: Mark Pearson <mpearson-lenovo@squebb.ca>
Cc: hdegoede@redhat.com, markgross@kernel.org,
	markpearson@lenovo.com, platform-driver-x86@vger.kernel.org
Subject: Re: [PATCH 1/2] platform/x86: think-lmi: add missing type attribute
Date: Sun, 12 Mar 2023 03:33:26 +0000	[thread overview]
Message-ID: <0bc6d16a-5c58-462b-92d5-d827d92b65ed@t-8ch.de> (raw)
In-Reply-To: <20230312024635.518769-1-mpearson-lenovo@squebb.ca>

On Sat, Mar 11, 2023 at 09:46:34PM -0500, Mark Pearson wrote:
> This driver was missing the mandatory type attribute...oops.
> 
> Add it in along with logic to determine whether the attribute is an
> enumeration type or a string by parsing the possible_values attribute.
> 
> Some platforms (and some attributes) don't return possible_values so to
> prevent trying to scan NULL strings mark these as "N/A".
> 
> Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=216460

Afaik Fixes: is only for references to commits.
Instead a Reported-by/Link would be better.

> Signed-off-by: Mark Pearson <mpearson-lenovo@squebb.ca>
> ---
>  drivers/platform/x86/think-lmi.c | 26 +++++++++++++++++++++++---
>  drivers/platform/x86/think-lmi.h |  6 ++++++
>  2 files changed, 29 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/platform/x86/think-lmi.c b/drivers/platform/x86/think-lmi.c
> index 86b33b74519b..495a5e045069 100644
> --- a/drivers/platform/x86/think-lmi.c
> +++ b/drivers/platform/x86/think-lmi.c
> @@ -941,12 +941,18 @@ static ssize_t possible_values_show(struct kobject *kobj, struct kobj_attribute
>  {
>  	struct tlmi_attr_setting *setting = to_tlmi_attr_setting(kobj);
>  
> -	if (!tlmi_priv.can_get_bios_selections)
> -		return -EOPNOTSUPP;
> -
>  	return sysfs_emit(buf, "%s\n", setting->possible_values);
>  }
>  
> +static ssize_t type_show(struct kobject *kobj, struct kobj_attribute *attr,
> +		char *buf)
> +{
> +	struct tlmi_attr_setting *setting = to_tlmi_attr_setting(kobj);
> +
> +	return sysfs_emit(buf, "%s\n",
> +			setting->type == TLMI_ENUMERATION ? "enumeration" : "string");
> +}
> +
>  static ssize_t current_value_store(struct kobject *kobj,
>  		struct kobj_attribute *attr,
>  		const char *buf, size_t count)
> @@ -1036,10 +1042,13 @@ static struct kobj_attribute attr_possible_values = __ATTR_RO(possible_values);
>  
>  static struct kobj_attribute attr_current_val = __ATTR_RW_MODE(current_value, 0600);
>  
> +static struct kobj_attribute attr_type = __ATTR_RO(type);
> +
>  static struct attribute *tlmi_attrs[] = {
>  	&attr_displ_name.attr,
>  	&attr_current_val.attr,
>  	&attr_possible_values.attr,
> +	&attr_type.attr,
>  	NULL
>  };
>  
> @@ -1424,6 +1433,17 @@ static int tlmi_analyze(void)
>  				pr_info("Error retrieving possible values for %d : %s\n",
>  						i, setting->display_name);
>  		}
> +		/* If we don't have a possible value mark as N/A */
> +		if (!setting->possible_values) {
> +			setting->possible_values = kmalloc(strlen("N/A"), GFP_KERNEL);

kmalloc() can fail.

> +			sprintf(setting->possible_values, "N/A");

This writes the '\0' out of bounds?

kmalloc() and sprintf() could be replaced with kstrdup().

Instead of having to do allocations, check for failure, worry about how
sysfs_emit() will handle the NULL it would be easier to just check of
NULL inside possible_values_show() and fall back to N/A there.

> +		}
> +		/* Figure out what setting type is as BIOS does not return this */
> +		if (strchr(setting->possible_values, ','))

possible_values could be NULL if the sprintf would not have dereferenced
it before.

> +			setting->type = TLMI_ENUMERATION;
> +		else
> +			setting->type = TLMI_STRING;
> +

Is it worth introducing a new enum and field in struct
tlmi_attr_setting?
The check could also be done directly in type_show().
(with a NULL-check).

>  		kobject_init(&setting->kobj, &tlmi_attr_setting_ktype);
>  		tlmi_priv.setting[i] = setting;
>  		kfree(item);
> diff --git a/drivers/platform/x86/think-lmi.h b/drivers/platform/x86/think-lmi.h
> index 4daba6151cd6..b76edcb9b1af 100644
> --- a/drivers/platform/x86/think-lmi.h
> +++ b/drivers/platform/x86/think-lmi.h
> @@ -27,6 +27,11 @@ enum level_option {
>  	TLMI_LEVEL_MASTER,
>  };
>  
> +enum attr_type {
> +	TLMI_ENUMERATION,
> +	TLMI_STRING,
> +};
> +
>  /* password configuration details */
>  struct tlmi_pwdcfg_core {
>  	uint32_t password_mode;
> @@ -73,6 +78,7 @@ struct tlmi_attr_setting {
>  	int index;
>  	char display_name[TLMI_SETTINGS_MAXLEN];
>  	char *possible_values;
> +	enum attr_type type;
>  };
>  
>  struct think_lmi {
> -- 
> 2.39.1
> 