Re: seccomp feature development

On Tue, May 19, 2020 at 12:39:39AM +0200, Jann Horn wrote:

quoted

For user_notif, I think we need something in and around these options:

- make a new API that explicitly follows EA struct design
  (and while read()/write() might be easier[4], I tend to agree with
  Jann and we need to stick to ioctl(): as Tycho noted, "read/write is
  for data". Though I wonder if read() could be used for the notifications,
  which ARE data, and use ioctl() for the responses?)

Just as a note: If we use read() there, we'll never be able to
transfer things like FDs through that API.

Although there is no good reason for read being able to receive FDs, there is
precedence for recvmsg being able to do this. Either way, I do not think
it's a good idea to recv file descriptors, and instead file descriptors
should be fetched via the pidfd_getfd syscall.

Injection is more complicated, and for now, I believe that "writes" should
be done via ioctl, or in the future, something like sendmsg might work.