linux-kernel - Re: [PATCH -next] scsi: hisi_sas: drop free_irq of devm_request

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Date:   Wed, 19 May 2021 12:19:09 +0100
From:   John Garry <john.garry@...wei.com>
To:     Yang Yingliang <yangyingliang@...wei.com>,
        <linux-kernel@...r.kernel.org>, <linux-scsi@...r.kernel.org>
CC:     <jejb@...ux.ibm.com>, <martin.petersen@...cle.com>,
        chenxiang <chenxiang66@...ilicon.com>,
        "luojiaxing@...wei.com" <luojiaxing@...wei.com>
Subject: Re: [PATCH -next] scsi: hisi_sas: drop free_irq of devm_request_irq
 allocated irq

On 19/05/2021 04:36, Yang Yingliang wrote:
> 
> On 2021/5/18 23:34, John Garry wrote:
>> On 18/05/2021 14:09, Yang Yingliang wrote:
>>> irq allocated with devm_request_irq should not be freed using
>>> free_irq, because doing so causes a dangling pointer, and a
>>> subsequent double free.
>>>
>>> Reported-by: Hulk Robot <hulkci@...wei.com>
>>> Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>
>>> ---
>>>   drivers/scsi/hisi_sas/hisi_sas_v3_hw.c | 6 +++---
>>>   1 file changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c 
>>> b/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
>>> index 499c770d405c..684f762bcfb3 100644
>>> --- a/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
>>> +++ b/drivers/scsi/hisi_sas/hisi_sas_v3_hw.c
>>> @@ -4811,9 +4811,9 @@ hisi_sas_v3_destroy_irqs(struct pci_dev *pdev, 
>>> struct hisi_hba *hisi_hba)
>>>   {
>>>       int i;
>>>   -    free_irq(pci_irq_vector(pdev, 1), hisi_hba);
>>> -    free_irq(pci_irq_vector(pdev, 2), hisi_hba);
>>> -    free_irq(pci_irq_vector(pdev, 11), hisi_hba);
>>> +    devm_free_irq(&pdev->dev, pci_irq_vector(pdev, 1), hisi_hba);
>>> +    devm_free_irq(&pdev->dev, pci_irq_vector(pdev, 2), hisi_hba);
>>> +    devm_free_irq(&pdev->dev, pci_irq_vector(pdev, 11), hisi_hba);
>>>       for (i = 0; i < hisi_hba->cq_nvecs; i++) {
>>>           struct hisi_sas_cq *cq = &hisi_hba->cq[i];
>>>           int nr = hisi_sas_intr_conv ? 16 : 16 + i;
>>>
>>
>> Does the free_irq(pci_irq_vector(pdev, nr, cq)) call also need to 
>> change (not shown)?
> Yes, I missed that, it should be changed too.

So I think that we need this addition:
  devm_free_irq(&pdev->dev, pci_irq_vector(pdev, nr), cq);

>>
>> Having said that, why have these at all if we use devm_request_irq()? 
>> devm_irq_release() calls free_irq().
> I keep the original logic here, only avoid double free.

Kasan doesn't complain. Anyway, I think we can't rely on device-managed 
method (for calling free_irq()) as it conflicts with pci free vectors 
call. I thought that someone was developed a device-managed version of 
that (pci_alloc_irq_vectors()).

Anyway, please proceed with your change, but with the suggested addition.

Thanks