On Mon, Jul 29, 2019 at 09:24:38AM -0700, Kees Cook wrote:
> On Sun, Jul 28, 2019 at 12:22:29AM +0200, Christian Brauner wrote:
> > diff --git a/kernel/exit.c b/kernel/exit.c
> > index a75b6a7f458a..64bb6893a37d 100644
> > --- a/kernel/exit.c
> > +++ b/kernel/exit.c
> > @@ -1552,6 +1552,23 @@ static long do_wait(struct wait_opts *wo)
> > return retval;
> > }
> >
> > +static struct pid *pidfd_get_pid(unsigned int fd)
> > +{
> > + struct fd f;
> > + struct pid *pid;
> > +
> > + f = fdget(fd);
> > + if (!f.file)
> > + return ERR_PTR(-EBADF);
> > +
> > + pid = pidfd_pid(f.file);
> > + if (!IS_ERR(pid))
> > + get_pid(pid);
> > +
> > + fdput(f);
> > + return pid;
> > +}
> > +
> > static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop,
> > int options, struct rusage *ru)
> > {
> > @@ -1574,19 +1591,29 @@ static long kernel_waitid(int which, pid_t upid,
> > struct waitid_info *infop,
> > type = PIDTYPE_PID;
> > if (upid <= 0)
> > return -EINVAL;
> > +
> > + pid = find_get_pid(upid);
> > break;
> > case P_PGID:
> > type = PIDTYPE_PGID;
> > if (upid <= 0)
> > return -EINVAL;
> > +
> > + pid = find_get_pid(upid);
> > + break;
> > + case P_PIDFD:
> > + type = PIDTYPE_PID;
> > + if (upid < 0)
> > + return -EINVAL;
> > +
> > + pid = pidfd_get_pid(upid);
> > + if (IS_ERR(pid))
> > + return PTR_ERR(pid);
>
> I spent some time convincing myself that this early bail out was
> correct. It seems this path is only reachable in the EBADF case, so that
> makes sense. The other failure modes in this switch all give a NULL pid
> so that the final do_wait() returns ECHILD. So, as long as that's
> intentional (which I think it is), this all looks fine. :)
Yep, it is. I didn't want to refactor that out of do_wait(). :)
Thanks!
Christian
>
> Reviewed-by: Kees Cook <[email protected]>
