[PATCH] iommu/amd: Check if domain is NULL before dereference it

[PATCH] iommu/amd: Check if domain is NULL before dereference it

[Baoquan He]

In get_domain(), 'domain' could still be NULL before it's passed to
dma_ops_domain() to dereference. For safety, check if 'domain' is
NULL before passing to dma_ops_domain().

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Baoquan He <bhe@redhat.com>
---
 drivers/iommu/amd_iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 16f1e6af00b0..2e2d5e6a13b3 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -2262,7 +2262,7 @@ static struct protection_domain *get_domain(struct device *dev)
 		domain = to_pdomain(io_domain);
 		attach_device(dev, domain);
 	}
-	if (!dma_ops_domain(domain))
+	if (domain && !dma_ops_domain(domain))
 		return ERR_PTR(-EBUSY);
 
 	return domain;
-- 
2.5.5

Re: [PATCH] iommu/amd: Check if domain is NULL before dereference it

[Dan Carpenter]

On Thu, Aug 24, 2017 at 07:56:47PM +0800, Baoquan He wrote:
> In get_domain(), 'domain' could still be NULL before it's passed to
> dma_ops_domain() to dereference. For safety, check if 'domain' is
> NULL before passing to dma_ops_domain().
> 
> Reported-by: Dan Carpenter <dan.carpenter-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> Signed-off-by: Baoquan He <bhe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> ---
>  drivers/iommu/amd_iommu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> index 16f1e6af00b0..2e2d5e6a13b3 100644
> --- a/drivers/iommu/amd_iommu.c
> +++ b/drivers/iommu/amd_iommu.c
> @@ -2262,7 +2262,7 @@ static struct protection_domain *get_domain(struct device *dev)
>  		domain = to_pdomain(io_domain);
>  		attach_device(dev, domain);
>  	}
> -	if (!dma_ops_domain(domain))
> +	if (domain && !dma_ops_domain(domain))
>  		return ERR_PTR(-EBUSY);
>  
>  	return domain;

This still doesn't look right.  None of the callers can handle a NULL
domain.

regards,
dan carpenter

Re: [PATCH] iommu/amd: Check if domain is NULL before dereference it

[Baoquan He]

On 08/24/17 at 03:11pm, Dan Carpenter wrote:
> On Thu, Aug 24, 2017 at 07:56:47PM +0800, Baoquan He wrote:
> > In get_domain(), 'domain' could still be NULL before it's passed to
> > dma_ops_domain() to dereference. For safety, check if 'domain' is
> > NULL before passing to dma_ops_domain().
> > 
> > Reported-by: Dan Carpenter <dan.carpenter-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> > Signed-off-by: Baoquan He <bhe-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> > ---
> >  drivers/iommu/amd_iommu.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> > index 16f1e6af00b0..2e2d5e6a13b3 100644
> > --- a/drivers/iommu/amd_iommu.c
> > +++ b/drivers/iommu/amd_iommu.c
> > @@ -2262,7 +2262,7 @@ static struct protection_domain *get_domain(struct device *dev)
> >  		domain = to_pdomain(io_domain);
> >  		attach_device(dev, domain);
> >  	}
> > -	if (!dma_ops_domain(domain))
> > +	if (domain && !dma_ops_domain(domain))
> >  		return ERR_PTR(-EBUSY);
> >  
> >  	return domain;
> 
> This still doesn't look right.  None of the callers can handle a NULL
> domain.

Here the NULL domain is on purpose. In kdump kernel if iommu is
pre-enabled, just stop attach the device to domain until the device
driver init. So here in driver init when call get_domain(), if found
get_dev_data(dev)->defer_attach is true, we just do the attachment of
device to domain.

Not sure if I got what you mean about 'callers'.

Re: [PATCH] iommu/amd: Check if domain is NULL before dereference it

[Dan Carpenter]

Take a look at this code for example.  But all the places which call
get_domain() are the same:

drivers/iommu/amd_iommu.c
  2648          page = virt_to_page(virt_addr);
  2649          size = PAGE_ALIGN(size);
  2650  
  2651          domain = get_domain(dev);
                         ^^^^^^^^^^^^^^
imagined get_domain() returns NULL.

  2652          if (IS_ERR(domain))
  2653                  goto free_mem;
  2654  
  2655          dma_dom = to_dma_ops_domain(domain);
                          ^^^^^^^^^^^^^^^^^^^^^^^^^
This will Oops.

  2656  

regards,
dan carpenter

Re: [PATCH] iommu/amd: Check if domain is NULL before dereference it

[Baoquan He]

On 08/24/17 at 03:32pm, Dan Carpenter wrote:
> Take a look at this code for example.  But all the places which call
> get_domain() are the same:
> 
> drivers/iommu/amd_iommu.c
>   2648          page = virt_to_page(virt_addr);
>   2649          size = PAGE_ALIGN(size);
>   2650  
>   2651          domain = get_domain(dev);
>                          ^^^^^^^^^^^^^^
> imagined get_domain() returns NULL.
> 
>   2652          if (IS_ERR(domain))
>   2653                  goto free_mem;
>   2654  
>   2655          dma_dom = to_dma_ops_domain(domain);
>                           ^^^^^^^^^^^^^^^^^^^^^^^^^
> This will Oops.

I see, it's a problem. Thanks for telling!

How about below change? But I am not very sure which errno should be
picked, seems the latter one, EBUSY is better since it has passed the
check_device() checking.

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 16f1e6af00b0..2d7d04472555 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -2262,6 +2262,9 @@ static struct protection_domain *get_domain(struct device *dev)
 		domain = to_pdomain(io_domain);
 		attach_device(dev, domain);
 	}
+	if (domain == NULL)
+		return ERR_PTR(-EBUSY);
+
 	if (!dma_ops_domain(domain))
 		return ERR_PTR(-EBUSY);
 
-- 
2.5.5

Re: [PATCH] iommu/amd: Check if domain is NULL before dereference it

[Dan Carpenter]

On Thu, Aug 24, 2017 at 08:47:33PM +0800, Baoquan He wrote:
> On 08/24/17 at 03:32pm, Dan Carpenter wrote:
> > Take a look at this code for example.  But all the places which call
> > get_domain() are the same:
> > 
> > drivers/iommu/amd_iommu.c
> >   2648          page = virt_to_page(virt_addr);
> >   2649          size = PAGE_ALIGN(size);
> >   2650  
> >   2651          domain = get_domain(dev);
> >                          ^^^^^^^^^^^^^^
> > imagined get_domain() returns NULL.
> > 
> >   2652          if (IS_ERR(domain))
> >   2653                  goto free_mem;
> >   2654  
> >   2655          dma_dom = to_dma_ops_domain(domain);
> >                           ^^^^^^^^^^^^^^^^^^^^^^^^^
> > This will Oops.
> 
> I see, it's a problem. Thanks for telling!
> 
> How about below change? But I am not very sure which errno should be
> picked, seems the latter one, EBUSY is better since it has passed the
> check_device() checking.

Looks good to me.  You know better than I do which errno is best, so
I'll leave that to you.

regards,
dan carpenter

Re: [PATCH] iommu/amd: Check if domain is NULL before dereference it

[Baoquan He]

On 08/24/17 at 03:53pm, Dan Carpenter wrote:
> On Thu, Aug 24, 2017 at 08:47:33PM +0800, Baoquan He wrote:
> > On 08/24/17 at 03:32pm, Dan Carpenter wrote:
> > > Take a look at this code for example.  But all the places which call
> > > get_domain() are the same:
> > > 
> > > drivers/iommu/amd_iommu.c
> > >   2648          page = virt_to_page(virt_addr);
> > >   2649          size = PAGE_ALIGN(size);
> > >   2650  
> > >   2651          domain = get_domain(dev);
> > >                          ^^^^^^^^^^^^^^
> > > imagined get_domain() returns NULL.
> > > 
> > >   2652          if (IS_ERR(domain))
> > >   2653                  goto free_mem;
> > >   2654  
> > >   2655          dma_dom = to_dma_ops_domain(domain);
> > >                           ^^^^^^^^^^^^^^^^^^^^^^^^^
> > > This will Oops.
> > 
> > I see, it's a problem. Thanks for telling!
> > 
> > How about below change? But I am not very sure which errno should be
> > picked, seems the latter one, EBUSY is better since it has passed the
> > check_device() checking.
> 
> Looks good to me.  You know better than I do which errno is best, so
> I'll leave that to you.

OK, thanks! Then let me post v2 with it.