Re: [PATCH] selftests: Open /dev/udmabuf O_RDONLY

[Jakub Kicinski]

On Wed, 1 Jul 2026 11:53:15 -0700 T.J. Mercier wrote:
> On Fri, Jun 26, 2026 at 6:09 PM Jakub Kicinski <kuba@xxxxxxxxxx> wrote:
> >
> > On Thu, 25 Jun 2026 11:15:55 -0700 T.J. Mercier wrote:  
> > > 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.

Alright, pop that into the commit msg and repost please.