linux-kernel - Re: [PATCH -next] iommu/dma: Fix missing mutex_init() in iommu_get_msi

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Message-ID: <a3fd3fef-f5fc-d89c-99de-4e7870cc9974@huawei.com>
Date:   Mon, 18 Jul 2022 14:42:39 +0800
From:   Yang Yingliang <yangyingliang@...wei.com>
To:     Robin Murphy <robin.murphy@....com>, Joerg Roedel <joro@...tes.org>
CC:     <linux-kernel@...r.kernel.org>, <iommu@...ts.linux.dev>,
        <iommu@...ts.linux-foundation.org>, <will@...nel.org>,
        <yf.wang@...iatek.com>
Subject: Re: [PATCH -next] iommu/dma: Fix missing mutex_init() in
 iommu_get_msi_cookie()

Hi,

On 2022/7/15 17:28, Robin Murphy wrote:
> On 2022-07-15 08:49, Joerg Roedel wrote:
>> Adding Robin.
>>
>> On Mon, Jun 27, 2022 at 04:55:33PM +0800, Yang Yingliang wrote:
>>> cookie_alloc() is called by iommu_get_dma_cookie() and 
>>> iommu_get_msi_cookie(),
>>> but the mutex is only initialized in iommu_get_dma_cookie(), move 
>>> mutex_init()
>>> into cookie_alloc() to make sure the mutex will be initialized.
>
> The mutex is only used in iommu_dma_init_domain(), which is only 
> called by iommu_setup_dma_ops() for IOMMU_DOMAIN_DMA domains. How is 
> there a problem here?
It's no problem now, but I thinks it's better to initialize the 'mutex' 
in cookie_alloc() to make code stronger.

Thanks,
Yang
>
> Robin.
>
>>> Fixes: ac9a5d522bb8 ("iommu/dma: Fix race condition during 
>>> iova_domain initialization")
>>> Reported-by: Hulk Robot <hulkci@...wei.com>
>>> Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>
>>> ---
>>>   drivers/iommu/dma-iommu.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
>>> index 1910f4f1612b..e29157380c48 100644
>>> --- a/drivers/iommu/dma-iommu.c
>>> +++ b/drivers/iommu/dma-iommu.c
>>> @@ -294,6 +294,7 @@ static struct iommu_dma_cookie 
>>> *cookie_alloc(enum iommu_dma_cookie_type type)
>>>       if (cookie) {
>>>           INIT_LIST_HEAD(&cookie->msi_page_list);
>>>           cookie->type = type;
>>> +        mutex_init(&cookie->mutex);
>>>       }
>>>       return cookie;
>>>   }
>>> @@ -311,7 +312,6 @@ int iommu_get_dma_cookie(struct iommu_domain 
>>> *domain)
>>>       if (!domain->iova_cookie)
>>>           return -ENOMEM;
>>>   -    mutex_init(&domain->iova_cookie->mutex);
>>>       return 0;
>>>   }
>>>   --
>>> 2.25.1
> .