linux-kernel - Re: [PATCH v2] acpi: Fix use-after-free in acpi

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Message-ID: <cbb62360-4f3f-6b74-996f-478af0752894@loongson.cn>
Date:   Fri, 27 Nov 2020 14:17:16 +0800
From:   Youling Tang <tangyouling@...ngson.cn>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] acpi: Fix use-after-free in acpi_ipmi.c

Hi,

On 11/26/2020 10:22 PM, Rafael J. Wysocki wrote:
> On Thu, Nov 26, 2020 at 2:26 AM Youling Tang <tangyouling@...ngson.cn> wrote:
>> kfree() has been called inside put_device so anther kfree would cause a
>> use-after-free bug.
>>
>> Signed-off-by: Youling Tang <tangyouling@...ngson.cn>
>> ---
>>   drivers/acpi/acpi_ipmi.c | 1 -
>>   1 file changed, 1 deletion(-)
>>
>> diff --git a/drivers/acpi/acpi_ipmi.c b/drivers/acpi/acpi_ipmi.c
>> index 9d6c0fc..18edf8b 100644
>> --- a/drivers/acpi/acpi_ipmi.c
>> +++ b/drivers/acpi/acpi_ipmi.c
>> @@ -142,7 +142,6 @@ static void ipmi_dev_release(struct acpi_ipmi_device *ipmi_device)
>>   {
>>          ipmi_destroy_user(ipmi_device->user_interface);
>>          put_device(ipmi_device->dev);
> Does putting ipmi_device->dev (which is a different object than
> ipmi_device itself) really cause ipmi_device to be freed
> automatically?  If not, the change below will introduce a memory leak.
>
ipmi_device will be free so that there is no memory leak.
Similar to the following:
https://lore.kernel.org/patchwork/patch/1342136/

Thanks,
Youling.
>> -       kfree(ipmi_device);
>>   }
>>
>>   static void ipmi_dev_release_kref(struct kref *kref)
>> --