[bug report] dma-buf: heaps: Add heap helpers

[bug report] dma-buf: heaps: Add heap helpers

[Dan Carpenter]

Hello John Stultz,

The patch 7b87ea704fd9: "dma-buf: heaps: Add heap helpers" from Oct
21, 2019, leads to the following static checker warning:

	drivers/dma-buf/heaps/heap-helpers.c:165 dma_heap_vm_fault()
	warn: uncapped user index 'buffer->pages[vmf->pgoff]'

drivers/dma-buf/heaps/heap-helpers.c
   160  static vm_fault_t dma_heap_vm_fault(struct vm_fault *vmf)
   161  {
   162          struct vm_area_struct *vma = vmf->vma;
   163          struct heap_helper_buffer *buffer = vma->vm_private_data;
   164  
   165          vmf->page = buffer->pages[vmf->pgoff];
                                          ^^^^^^^^^^
Smatch for some reason thinks this needs to be checked.  Smatch also
gets confused by these fault handlers and thinks there is some recursion
involved...

   166          get_page(vmf->page);
   167  
   168          return 0;
   169  }
   170  
   171  static const struct vm_operations_struct dma_heap_vm_ops = {
   172          .fault = dma_heap_vm_fault,
   173  };
   174  

regards,
dan carpenter
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Re: [bug report] dma-buf: heaps: Add heap helpers

[John Stultz]

On Thu, Oct 31, 2019 at 4:07 AM Dan Carpenter <dan.carpenter@oracle.com> wrote:
> The patch 7b87ea704fd9: "dma-buf: heaps: Add heap helpers" from Oct
> 21, 2019, leads to the following static checker warning:
>
>         drivers/dma-buf/heaps/heap-helpers.c:165 dma_heap_vm_fault()
>         warn: uncapped user index 'buffer->pages[vmf->pgoff]'
>
> drivers/dma-buf/heaps/heap-helpers.c
>    160  static vm_fault_t dma_heap_vm_fault(struct vm_fault *vmf)
>    161  {
>    162          struct vm_area_struct *vma = vmf->vma;
>    163          struct heap_helper_buffer *buffer = vma->vm_private_data;
>    164
>    165          vmf->page = buffer->pages[vmf->pgoff];
>                                           ^^^^^^^^^^
> Smatch for some reason thinks this needs to be checked.  Smatch also
> gets confused by these fault handlers and thinks there is some recursion
> involved...

Hrm, I'm not totally sure I grok what it's looking for, but I'm
guessing it's suggesting we check that pgoff isn't larger then the
pagecount?
I'll add that check in, but let me know if I've misunderstood.

Thanks for the report!
-john
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Re: [bug report] dma-buf: heaps: Add heap helpers

[Dan Carpenter]

On Fri, Nov 01, 2019 at 12:31:53PM -0700, John Stultz wrote:
> On Thu, Oct 31, 2019 at 4:07 AM Dan Carpenter <dan.carpenter@oracle.com> wrote:
> > The patch 7b87ea704fd9: "dma-buf: heaps: Add heap helpers" from Oct
> > 21, 2019, leads to the following static checker warning:
> >
> >         drivers/dma-buf/heaps/heap-helpers.c:165 dma_heap_vm_fault()
> >         warn: uncapped user index 'buffer->pages[vmf->pgoff]'
> >
> > drivers/dma-buf/heaps/heap-helpers.c
> >    160  static vm_fault_t dma_heap_vm_fault(struct vm_fault *vmf)
> >    161  {
> >    162          struct vm_area_struct *vma = vmf->vma;
> >    163          struct heap_helper_buffer *buffer = vma->vm_private_data;
> >    164
> >    165          vmf->page = buffer->pages[vmf->pgoff];
> >                                           ^^^^^^^^^^
> > Smatch for some reason thinks this needs to be checked.  Smatch also
> > gets confused by these fault handlers and thinks there is some recursion
> > involved...
> 
> Hrm, I'm not totally sure I grok what it's looking for, but I'm
> guessing it's suggesting we check that pgoff isn't larger then the
> pagecount?
> I'll add that check in, but let me know if I've misunderstood.

Yeah, that's right.  Or maybe pgoff is checked somewhere else?

regards,
dan carpenter

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