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. > 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, 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.
