Re: [PATCH v2 0/5] pid: add pidfd_open()

[Daniel Colascione]

On Sat, Mar 30, 2019 at 9:09 AM Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Fri, Mar 29, 2019 at 8:54 AM Christian Brauner <christian@xxxxxxxxxx> wrote:
> >
> > /* Introduction */
> > This adds the pidfd_open() syscall.
> > pidfd_open() allows to retrieve file descriptors for a given pid. This
> > includes both file descriptors for processes and file descriptors for
> > threads.
>
> I'm ok with the pidfd_open() call to just get a pidfd, but that
> "pidfd_to_profs()" needs to go away.
>
> If you want to open the /proc/<pid>/status file, then just do that.
> This whole "do one and convert to the other" needs to die. No, no, no.

How do you propose that someone open the /proc/<pid>/status file in a
race-free manner starting with the result of calling pidfd_open?