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

[Yang Yingliang]

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@xxxxxxxxxx>
> > > Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx>
> > > ---
> > >   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
> .