On Fri, Jun 26, 2026 at 6:09 PM Jakub Kicinski [off-list ref] wrote:

On Thu, 25 Jun 2026 11:15:55 -0700 T.J. Mercier wrote:

quoted

Write permissions on the /dev/udmabuf device file are not required to
issue ioctls and allocate udmabufs. Applications should be opening this
file as O_RDONLY. The BPF dmabuf_iter selftest already does this. [1]

Remove the write access mode from the drivers/dma-buf/udmabuf.c and
drivers/net/hw/ncdevmem.c selftests.

You need to explain "why", too. Why change it if it clearly
worked for everyone running this test until now.
--
pw-bot: cr

Principle of least privilege. Folks use or point to these selftests as
examples, and then wonder why O_RDWR doesn't work on systems where
write permissions are not available on /dev/udmabuf.