Re: [PATCH v7 2/9] pidfd: Add missing sock updates for pidfd_getfd()

[Kees Cook <keescook@chromium.org>]

On Thu, Jul 09, 2020 at 10:00:42PM +0200, Jann Horn wrote:
> On Thu, Jul 9, 2020 at 8:26 PM Kees Cook <keescook@chromium.org> wrote:
> > The sock counting (sock_update_netprioidx() and sock_update_classid())
> > was missing from pidfd's implementation of received fd installation. Add
> > a call to the new __receive_sock() helper.
> [...]
> > diff --git a/kernel/pid.c b/kernel/pid.c
> [...]
> > @@ -642,10 +643,12 @@ static int pidfd_getfd(struct pid *pid, int fd)
> >         }
> >
> >         ret = get_unused_fd_flags(O_CLOEXEC);
> > -       if (ret < 0)
> > +       if (ret < 0) {
> >                 fput(file);
> > -       else
> > +       } else {
> >                 fd_install(ret, file);
> > +               __receive_sock(file);
> > +       }
> 
> __receive_sock() has to be before fd_install(), otherwise `file` can
> be a dangling pointer.

I've swapped the order now and double-checked the other uses. Everything
else seems fine.

-- 
Kees Cook