On Sun, Nov 18, 2018 at 01:28:41PM -0700, Andy Lutomirski wrote: > > > > On Nov 18, 2018, at 12:44 PM, Daniel Colascione <dancol@xxxxxxxxxx> wrote: > > > > > > > That is, I'm proposing an API that looks like this: > > > > int process_kill(int procfs_dfd, int signo, const union sigval value) > > > > If, later, process_kill were to *also* accept process-capability FDs, > > nothing would break. > > Except that this makes it ambiguous to the caller as to whether their current creds are considered. So it would need to be a different syscall or at least a flag. Otherwise a lot of those nice theoretical properties go away. I can add a flag argument int process_signal(int procfs_dfd, int signo, siginfo_t *info, int flags) The way I see it process_signal() should be equivalent to kill(pid, signal) for now. That is siginfo_t is cleared and set to: info.si_signo = sig; info.si_errno = 0; info.si_code = SI_USER; info.si_pid = task_tgid_vnr(current); info.si_uid = from_kuid_munged(current_user_ns(), current_uid()); > > > Yes, that's what I have in mind. A siginfo_t is small enough that we > > could just store it as a blob allocated off the procfs inode or > > something like that without bothering with a shmfs file. You'd be able > > to read(2) the exit status as many times as you wanted. > > I think that, if the syscall in question is read(2), then it should work *once* per struct file. Otherwise running cat on the file would behave very oddly. > > Read and poll have the same problem as write: we can’t check caps in read or poll either.
