On Fri, Nov 26, 2021 at 08:56:27AM +0000, Lee Jones wrote:
> On Fri, 26 Nov 2021, Dan Carpenter wrote:
>
> > On Thu, Nov 25, 2021 at 06:18:22PM +0300, Dan Carpenter wrote:
> > > I had thought that ->kmap_cnt was a regular int and not an unsigned
> > > int, but I would have to pull a stable tree to see where I misread the
> > > code.
> >
> > I was looking at (struct ion_buffer)->kmap_cnt but this is
> > (struct ion_handle)->kmap_cnt. I'm not sure how those are related but
> > it makes me nervous that one can go higher than the other. Also both
> > probably need overflow protection.
> >
> > So I guess I would just do something like:
> >
> > diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
> > index 806e9b30b9dc8..e8846279b33b5 100644
> > --- a/drivers/staging/android/ion/ion.c
> > +++ b/drivers/staging/android/ion/ion.c
> > @@ -489,6 +489,8 @@ static void *ion_buffer_kmap_get(struct ion_buffer *buffer)
> > void *vaddr;
> >
> > if (buffer->kmap_cnt) {
> > + if (buffer->kmap_cnt == INT_MAX)
> > + return ERR_PTR(-EOVERFLOW);
> > buffer->kmap_cnt++;
> > return buffer->vaddr;
> > }
> > @@ -509,6 +511,8 @@ static void *ion_handle_kmap_get(struct ion_handle *handle)
> > void *vaddr;
> >
> > if (handle->kmap_cnt) {
> > + if (handle->kmap_cnt == INT_MAX)
> > + return ERR_PTR(-EOVERFLOW);
> > handle->kmap_cnt++;
> > return buffer->vaddr;
> > }
>
> Which is all well and good until somebody changes the type.
That's hard to do on code that is removed from the kernel tree :)
