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

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Message-ID: <20170824125311.ymx27viis6rnhozy@mwanda>
Date:   Thu, 24 Aug 2017 15:53:12 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Baoquan He <bhe@...hat.com>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        joro@...tes.org
Subject: Re: [PATCH] iommu/amd: Check if domain is NULL before dereference it

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