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Date:   Thu, 26 Nov 2020 09:16:14 +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] acpi: Fix use-after-free in acpi_ipmi.c


Hi,
On 11/25/2020 11:53 PM, Rafael J. Wysocki wrote:
> On Tue, Nov 24, 2020 at 1:51 PM 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 | 2 --
>>   1 file changed, 2 deletions(-)
>>
>> diff --git a/drivers/acpi/acpi_ipmi.c b/drivers/acpi/acpi_ipmi.c
>> index 9d6c0fc..72902b6 100644
>> --- a/drivers/acpi/acpi_ipmi.c
>> +++ b/drivers/acpi/acpi_ipmi.c
>> @@ -130,7 +130,6 @@ ipmi_dev_alloc(int iface, struct device *dev, acpi_handle handle)
>>                                 ipmi_device, &user);
>>          if (err) {
>>                  put_device(dev);
>> -               kfree(ipmi_device);
> dev doesn't point to the same object in memory as ipmi_device, though,
> if I'm not mistaken.
>
> Please double check that and resend the patch if you are sure that it
> is correct.
You're right, dev really doesn't point to the same memory object
as ipmi_device. I'll send v2 later.

Thanks,
Youling.
>>                  return NULL;
>>          }
>>          ipmi_device->user_interface = user;
>> @@ -142,7 +141,6 @@ static void ipmi_dev_release(struct acpi_ipmi_device *ipmi_device)
>>   {
>>          ipmi_destroy_user(ipmi_device->user_interface);
>>          put_device(ipmi_device->dev);
>> -       kfree(ipmi_device);
>>   }
>>
>>   static void ipmi_dev_release_kref(struct kref *kref)
>> --
>> 2.1.0
>>

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