Re: [PATCH 1/5] hisi_acc_vfio_pci: Fixes a memory leak bug

[liulongfang]

On 2022/9/21 1:03, Shameerali Kolothum Thodi wrote:
> 
> 
>> -----Original Message-----
>> From: Jason Gunthorpe [mailto:jgg@xxxxxxxxxx]
>> Sent: 20 September 2022 17:38
>> To: Alex Williamson <alex.williamson@xxxxxxxxxx>
>> Cc: liulongfang <liulongfang@xxxxxxxxxx>; Shameerali Kolothum Thodi
>> <shameerali.kolothum.thodi@xxxxxxxxxx>; cohuck@xxxxxxxxxx;
>> linux-kernel@xxxxxxxxxxxxxxx; linuxarm@xxxxxxxxxxxxx
>> Subject: Re: [PATCH 1/5] hisi_acc_vfio_pci: Fixes a memory leak bug
>>
>> On Tue, Sep 20, 2022 at 10:34:43AM -0600, Alex Williamson wrote:
>>> On Thu, 15 Sep 2022 09:31:53 +0800
>>> Longfang Liu <liulongfang@xxxxxxxxxx> wrote:
>>>
>>>> During the stop copy phase of live migration, the driver allocates a
>>>> memory for the migrated data to save the data.
>>>>
>>>> When an exception occurs when the driver reads device data, the
>>>> driver will report an error to qemu and exit the current migration state.
>>>> But this memory is not released, which will lead to a memory leak
>>>> problem.
>>
>> Why isn't it released? The fput() releases it:
>>
>> static int hisi_acc_vf_release_file(struct inode *inode, struct file *filp) {
>> 	struct hisi_acc_vf_migration_file *migf = filp->private_data;
>>
>> 	hisi_acc_vf_disable_fd(migf);
>> 	mutex_destroy(&migf->lock);
>> 	kfree(migf);
>>         ^^^^^^^^^^
>>
>> This patch looks wrong to me.
> 
> That's right. Missed that. Sorry of the oversight.
> 
Yes, fput will call release in ops of file, here will call hisi_acc_vf_release_file
to complete the release operation of migf, so this patch is unnecessary.

But there is another place that needs to be modified:
hisi_acc_vf_disable_fd in hisi_acc_vf_disable_fds is not needed,
because it will have an fput next. Is this correct?

> Thanks,
> Shameer
> 
> .
Thanks,
Longfang.
>