Re: [GIT PULL] Please pull proc and exec work for 5.7-rc1

Jann Horn
2020-04-30T03:41:37Z

On Thu, Apr 30, 2020 at 5:26 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Wed, Apr 29, 2020 at 8:00 PM Jann Horn <jannh@google.com> wrote:
> >
> > But if we go with Bernd's approach together with your restart
> > suggestion,
>
> So repeat after me: Bernd's approach _without_ the restart is unacceptable.
>
> It's unacceptable because it breaks things that currently work, and
> returns EAGAIN in situations where that is simple not a valid error
> code.

Sure, makes sense to me. I'm not eager to start randomly throwing
EAGAIN where it couldn't happen before either (and I initially missed
that Bernd's patch did that for procfs files, too).

> That bug has nothing to do with ptrace(). It's literally a "write()"
> to a file in /proc.
>
> What is so hard to get about this basic thing?

You said:

| So a ptrace() user (or [...] wouldn't even see the impossible EAGAIN error.

So I assumed you explicitly wanted ptrace() to restart, too. I was
just pointing out that that didn't make sense to me.