linux-kernel - Re: [PATCH v2] platform/x86: think-lmi: Fix memory leak when showing current settings

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Message-ID: <7dae767a-51e3-2b3f-3396-7e8193300ac7@gmx.de>
Date:   Fri, 31 Mar 2023 23:26:49 +0200
From:   Armin Wolf <W_Armin@....de>
To:     Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>,
        markpearson@...ovo.com
Cc:     hdegoede@...hat.com, markgross@...nel.org, thomas@...ch.de,
        gregkh@...uxfoundation.org, rafael@...nel.org,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] platform/x86: think-lmi: Fix memory leak when showing
 current settings

Am 31.03.23 um 21:34 schrieb Mirsad Goran Todorovac:

> On 31. 03. 2023. 20:09, Armin Wolf wrote:
>> When retriving a item string with tlmi_setting(), the result has to be
>> freed using kfree(). In current_value_show() however, malformed
>> item strings are not freed, causing a memory leak.
>> Fix this by eliminating the early return responsible for this.
>>
>> Reported-by: Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
>> Link: https://lore.kernel.org/platform-driver-x86/01e920bc-5882-ba0c-dd15-868bf0eca0b8@alu.unizg.hr/T/#t
>> Fixes: a40cd7ef22fb ("platform/x86: think-lmi: Add WMI interface support on Lenovo platforms")
>> Signed-off-by: Armin Wolf <W_Armin@....de>
>> ---
>> Changes in v2:
>> - Add Reported-by: and Link: tags
>> ---
>>   drivers/platform/x86/think-lmi.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/platform/x86/think-lmi.c b/drivers/platform/x86/think-lmi.c
>> index cc66f7cbccf2..8cafb9d4016c 100644
>> --- a/drivers/platform/x86/think-lmi.c
>> +++ b/drivers/platform/x86/think-lmi.c
>> @@ -930,10 +930,12 @@ static ssize_t current_value_show(struct kobject *kobj, struct kobj_attribute *a
>>   	/* validate and split from `item,value` -> `value` */
>>   	value = strpbrk(item, ",");
>>   	if (!value || value == item || !strlen(value + 1))
>> -		return -EINVAL;
>> +		ret = -EINVAL;
>> +	else
>> +		ret = sysfs_emit(buf, "%s\n", value + 1);
>>
>> -	ret = sysfs_emit(buf, "%s\n", value + 1);
>>   	kfree(item);
>> +
>>   	return ret;
>>   }
> Hi, Armin,
>
> You might have wanted it to be tested in the original setting?
>
> Should this patch work as a standalone fix, without the others?
>
> This part:
>
> @@ -929,8 +929,10 @@ static ssize_t current_value_show(struct kobject *kobj, struct kobj_attribute *a
>
>          /* validate and split from `item,value` -> `value` */
>          value = strpbrk(item, ",");
> -       if (!value || value == item || !strlen(value + 1))
> +       if (!value || value == item || !strlen(value + 1)) {
> +               kfree(item);
>                  return -EINVAL;
> +       }
>
>          ret = sysfs_emit(buf, "%s\n", value + 1);
>          kfree(item);
>
> was apparently superseded.

Hi,

this part is indeed superseded by the patch, and it should work as a standalone fix.
I thought it might be better to have two patches for those two memory leaks, as they
are not directly connected.

> Should this one be applied? I guess it should, as I stated in email
> <4dc118c2-0dde-bd5e-ea41-427ed33e4545@....unizg.hr> from 2023-03-29 20:49 UTC+02:
>
> @@ -1457,10 +1458,10 @@ static int tlmi_analyze(void)
>                           * name string.
>                           * Try and pull that out if it's available.
>                           */
> -                       char *item, *optstart, *optend;
> +                       char *optitem, *optstart, *optend;
>
> -                       if (!tlmi_setting(setting->index, &item, LENOVO_BIOS_SETTING_GUID)) {
> -                               optstart = strstr(item, "[Optional:");
> +                       if (!tlmi_setting(setting->index, &optitem, LENOVO_BIOS_SETTING_GUID)) {
> +                               optstart = strstr(optitem, "[Optional:");
>                                  if (optstart) {
>                                          optstart += strlen("[Optional:");
>                                          optend = strstr(optstart, "]");
> @@ -1469,6 +1470,7 @@ static int tlmi_analyze(void)
>                                                          kstrndup(optstart, optend - optstart,
>                                                                          GFP_KERNEL);
>                                  }
> +                               kfree(optitem);
>                          }
>                  }
>                  /*
>
> If Mark had found a better fix, then that one goes away, too.
>
> NOTE PLEASE that in the above-mentioned message (like all the others) I just specified the
> commit at which the test kernel was built + all the applied patches (git diff did not give
> authors).
>
> This did not imply that I claim Mr. Weißschuh's fix for tlmi_analyze() return, God forbid!
> I apologise if I made room for such an impression.
>
> That's all, I think. Thank Heavens. God bless!
>
> I will assume the test build on the bottom patch + the Thomas's patch still apply + your patch.

All good.

Armin Wolf

> Best regards,
> Mirsad
>