lkml.org 
[lkml]   [2019]   [Apr]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 0/5] pid: add pidfd_open()
On Sun, Mar 31, 2019 at 08:13:38PM -0600, Andy Lutomirski wrote:
>
>
> > On Mar 31, 2019, at 3:17 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote:
> >
> >> On Sun, Mar 31, 2019 at 2:10 PM Christian Brauner <christian@brauner.io> wrote:
> >>
> >> I don't think that we want or can make them equivalent since that would
> >> mean we depend on procfs.
> >
> > Sure we can.
> >
> > If /proc is enabled, then you always do that dance YOU ALREADY WROTE
> > THE CODE FOR to do the stupid ioctl.
> >
> > And if /procfs isn't enabled, then you don't do that.
> >
> > Ta-daa. Done. No stupid ioctl, and now /proc and pidfd_open() return
> > the same damn thing.
> >
> > And guess what? If /proc isn't enabled, then obviously pidfd_open()
> > gives you the /proc-less thing, but at least there is no crazy "two
> > different file descriptors for the same thing" situation, because then
> > the /proc one doesn't exist.
> >
>
> I wish we could do this, and, in a clean design, it would be a no-brainer. But /proc has too much baggage. Just to mention two such things, there’s “net” and “../sys”. This crud is why we have all kinds of crazy rules that prevent programs in sandboxes from making a new mounts and mounting /proc in it. If we make it possible to clone a new process and this access /proc without having /proc mounted, we’ll open up a big can of worms.
>
> Maybe we could have a sanitized view of /proc and make a pidfd be a directory fd pointing at that.

We can also just create something like an internal bind-mount without a
parent, i.e. similar to

open_tree(<internal-procfs-mount>, "<pid>", OPEN_TREE_CLONE);

on a clone(CLONE_PIDFD);

that would block any openat(fd, "..");

\
 
 \ /
  Last update: 2019-04-01 14:05    [W:0.319 / U:21.016 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site