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

[John Stultz]

On Tue, Aug 11, 2026 at 1:41 PM 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.
>
> 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: John Stultz <jstultz@xxxxxxxxxx>

thanks
-john