On Sun, Nov 18, 2018 at 8:17 AM, Andy Lutomirski <luto@xxxxxxxxxx> wrote: > On Sun, Nov 18, 2018 at 7:53 AM Daniel Colascione <dancol@xxxxxxxxxx> wrote: >> >> On Sun, Nov 18, 2018 at 7:38 AM, Andy Lutomirski <luto@xxxxxxxxxx> wrote: >> > I fully agree that a more comprehensive, less expensive API for >> > managing processes would be nice. But I also think that this patch >> > (using the directory fd and ioctl) is better from a security >> > perspective than using a new file in /proc. >> >> That's an assertion, not an argument. And I'm not opposed to an >> operation on the directory FD, now that it's clear Linus has banned >> "write(2)-as-a-command" APIs. I just insist that we implement the API >> with a system call instead of a less-reliable ioctl due to the >> inherent namespace collision issues in ioctl command names. > > Linus banned it because of bugs iike the ones in the patch. Maybe: he didn't provide a reason. What's your point? >> > I have an old patch to make proc directory fds pollable: >> > >> > https://lore.kernel.org/patchwork/patch/345098/ >> > >> > That patch plus the one in this thread might make a nice addition to >> > the kernel even if we expect something much better to come along >> > later. >> >> I've always commented on that patch. You never addressed my technical >> objections. Why are you bringing up this patch again as if that >> discussion had never happened? To review, that patch has various race >> conditions > > I don't think I ever saw that review. https://lore.kernel.org/lkml/CAKOZuevXXqwJepmLNUtrU=f8jtdgdKAzUAnAA2+KVcWoMxMyFg@xxxxxxxxxxxxxx/ >> and even if it were technically correct, it'd be an abuse >> of directory objects (in what other circumstance do we poll >> directories?) and not logically generalizable to a model in which we >> expose process exit status via the exit-monitoring API. > > I agree it's weird. It might be better to have /proc/PID/exit_status > and make *that* pollable. That's exactly what my patch provides. I feel like we're rehashing the previous discussion.
