Re: [PATCH] kselftests: dmabuf-heaps: Open heap device files O_RDONLY

[T.J. Mercier]

On Wed, Aug 12, 2026 at 8:02 AM Sumit Semwal <sumit.semwal@xxxxxxxxxx> wrote:
>
> Hello T J,
>
> On Wed, 12 Aug 2026 at 02:11, T.J. Mercier <tjmercier@xxxxxxxxxx> wrote:
> >
> > Write permissions on the /dev/dma_heap/* device files are not required
> > to issue ioctls and allocate dmabufs. Applications should be opening
> > these file as O_RDONLY. The BPF dmabuf_iter selftest already does
> > this. [1]
> >
> > Users are pointing to these selftests as examples of how use dmabuf,
> > and encountering permission errors on systems where write permissions
> > are not available on /dev/dma_heap/*. Apply the principle of least
> > privilege to selftests which open dmabuf heaps by removing the write
> > access mode and using O_RDONLY for the open() instead.
>
> Thanks for the patch.
> >
> > The same is true for the vgem test using /dev/dri/card.
> >
> > [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c?h=v7.1#n49
> >
> > Signed-off-by: T.J. Mercier <tjmercier@xxxxxxxxxx>
> Acked-by: Sumit Semwal <sumit.semwal@xxxxxxxxxx>

Thanks for the quick revieews John, Christian, and Sumit!