On Mon, Jan 13, 2020 at 11:10 AM Christian Brauner <christian.brauner@xxxxxxxxxx> wrote: > This does not > affect the permission checking you're performing here. Pidfds-as-capabilities sounds like a good change. Can you clarify what you mean here though? Do you mean that in order to perform some process-directed operation X on process Y, the pidfd passed to X must have been opened with PIDFD_CAP_X *and* the process *using* the pidfds must be able to perform operation X on process Y? Or do pidfds in this model "carry" permissions in the same way that an ordinary file descriptor "carries" the ability to write to a file if it was opened with O_WRONLY even if the FD is passed to a process that couldn't otherwise write to that file? Right now, pidfds are identity-only and always rely on the caller's permissions. I like the capability bit model because it makes pidfds more consistent with other file descriptors and enabled delegation of capabilities across the system.
