Re: [RFC v1] USB: core: add USBDEVFS_REVOKE ioctl

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Tue, Apr 26, 2022 at 12:07:32PM +0200, Bastien Nocera wrote:
> On Tue, 2022-04-26 at 10:46 +0200, Oliver Neukum wrote:
> > 
> > 
> > On 26.04.22 09:21, Greg Kroah-Hartman wrote:
> > > Yes, but, it's not so simple.  Many people have asked for revoke()
> > > to be
> > > added as a syscall like is in the BSDs, but the BSDs only allow
> > > that for
> > > a very small subset of file descriptor types, and doing it in a
> > > generic
> > > fashion seems very difficult (I tried a few years ago and gave up,
> > > but
> > > my knowledge of the vfs layer is minimal.)
> > Well, then we should go for the minimalist approach and just
> > add a hook to VFS. Multiple different ioctl()s are definitely a bad
> > idea.
> > An frevoke() looks much easier to do than one based on paths.
> > If I understand the issue behind the proposal correctly the caller
> > has opened the device.
> 
> Doesn't look like FreeBSD at least has an frevoke() syscall anymore, it
> had an FREVOKE flag, which is now a define for the O_VERIFY option
> which has quite different semantics:
> https://www.freebsd.org/cgi/man.cgi?sektion=2&query=open

Take a look at this implementation:
	https://man.openbsd.org/revoke.2