linux-kernel - Re: [External] [PATCH] platform/x86: think-lmi: Fix reference leak

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Date:   Mon, 25 Sep 2023 16:26:00 +0200
From:   Armin Wolf <W_Armin@....de>
To:     Mark Pearson <markpearson@...ovo.com>
Cc:     hdegoede@...hat.com, markgross@...nel.org,
        ilpo.jarvinen@...ux.intel.com, platform-driver-x86@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [External] [PATCH] platform/x86: think-lmi: Fix reference leak

Am 25.09.23 um 16:00 schrieb Mark Pearson:

> Thanks Armin,
>
> On 9/23/23 16:41, Armin Wolf wrote:
>> If a duplicate attribute is found using kset_find_obj(), a reference
>> to that attribute is returned which needs to be disposed accordingly
>> using kobject_put(). Move the setting name validation into a separate
>> function to allow for this change without having to duplicate the
>> cleanup code for this setting.
>> As a side note, a very similar bug was fixed in
>> commit 7295a996fdab ("platform/x86: dell-sysman: Fix reference leak"),
>> so it seems that the bug was copied from that driver.
>>
>> Compile-tested only.
>>
>> Fixes: 1bcad8e510b2 ("platform/x86: think-lmi: Fix issues with
>> duplicate attributes")
>> Signed-off-by: Armin Wolf <W_Armin@....de>
>> ---
>>   drivers/platform/x86/think-lmi.c | 24 ++++++++++++++++++++----
>>   1 file changed, 20 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/platform/x86/think-lmi.c
>> b/drivers/platform/x86/think-lmi.c
>> index 4be6f28d4600..3a396b763c49 100644
>> --- a/drivers/platform/x86/think-lmi.c
>> +++ b/drivers/platform/x86/think-lmi.c
>> @@ -1344,6 +1344,24 @@ static void tlmi_release_attr(void)
>>       kset_unregister(tlmi_priv.authentication_kset);
>>   }
>>
>> +static int tlmi_validate_setting_name(struct kset *attribute_kset,
>> char *name)
>> +{
>> +    struct kobject *duplicate;
>> +
>> +    if (!strcmp(name, "Reserved"))
>> +        return -EINVAL;
>> +
>> +    duplicate = kset_find_obj(attribute_kset, name);
>> +    if (duplicate) {
>> +        pr_debug("Duplicate attribute name found - %s\n", name);
>> +        /* kset_find_obj() returns a reference */
>> +        kobject_put(duplicate);
>> +        return -EBUSY;
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>>   static int tlmi_sysfs_init(void)
>>   {
>>       int i, ret;
>> @@ -1372,10 +1390,8 @@ static int tlmi_sysfs_init(void)
>>               continue;
>>
>>           /* check for duplicate or reserved values */
>> -        if (kset_find_obj(tlmi_priv.attribute_kset,
>> tlmi_priv.setting[i]->display_name) ||
>> -            !strcmp(tlmi_priv.setting[i]->display_name, "Reserved")) {
>> -            pr_debug("duplicate or reserved attribute name found -
>> %s\n",
>> -                tlmi_priv.setting[i]->display_name);
>> +        if (tlmi_validate_setting_name(tlmi_priv.attribute_kset,
>> + tlmi_priv.setting[i]->display_name) < 0) {
>>               kfree(tlmi_priv.setting[i]->possible_values);
>>               kfree(tlmi_priv.setting[i]);
>>               tlmi_priv.setting[i] = NULL;
>> --
>> 2.39.2
>>
>
> Reviewed-by: Mark Pearson <mpearson-lenovo@...ebb.ca>
>
> Do you have any reports of our platforms where these are seen? If so
> I'd like to get it fixed in FW too (and I can get it tested on HW if
> that helps)
>
> Mark
>
No, i do not have any reports regarding this issue. I stumbled upon this bug by chance, after fixing a similar bug in dell-wmi-sysman.
I suspect that the bug was copied from there to the other drivers, like think-lmi and hp-bioscfg.

Armin Wolf