Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <CAHk-=whJttTNFQn1fMYp91LZ90iHE7B2THZ8NjQ7fBwmWX9k6w@mail.gmail.com>
 <CAHk-=wi_zr9dwX3UBYvgkmm6eVQfRP50orryJ6ZVAxuFqdSG5A@mail.gmail.com>
 <20200428190836.GC29960@redhat.com> <CAHk-=wi03QRcUR1DfbEr+Pw-DAMENzY-FuRcGawtj9p597=p2w@mail.gmail.com>
 <CAG48ez03ABTa-KbCtFHqB1hOT7dgAM96c3kiw-e80B+utSEwYw@mail.gmail.com>
 <CAHk-=wjTLnMuZmBO2foeHhsLAoUTpUi7oBVJ67F4XKB+tdEDbQ@mail.gmail.com>
 <CAG48ez3EQOvdbzu9aO-cEAJwF_=fJzn1Cg0LMs3ruc=5r1ie5w@mail.gmail.com>
 <CAHk-=whTgFbjGTP=CqMWs_LOkY7bWvLQGYKwKx86amdbMovAkw@mail.gmail.com>
 <CAG48ez2-Nu2ALN6VEUZL-prtR_Kk8QYBHcnvuh0aU2e4zf37RA@mail.gmail.com>
 <CAHk-=wh=G47oD2F1CgOrvGFbEPh2ddMKLV4_wV_bs6S=98aZ5A@mail.gmail.com>
 <AM6PR03MB5170A6AA240D2E8F5E88B911E4AD0@AM6PR03MB5170.eurprd03.prod.outlook.com>
 <CAHk-=wguiKq8yf11WJjgSL4ADKZ5sLe_Qbd7vHEqAkTvZJ+d+Q@mail.gmail.com>
 <CAHk-=wjUZLybZBJgOtD2gng=FS7USrbQQ1-tn5M+UP5DbCWdzw@mail.gmail.com>
 <CAG48ez0FL3i4eGFYryOwG2nnS+JigfKYAVSV9ogVHjmjOWzsrA@mail.gmail.com>
 <AM6PR03MB5170C5D02C6FCB6D69DFE3ADE4AA0@AM6PR03MB5170.eurprd03.prod.outlook.com>
 <CAHk-=wg6oKSLkVhY5oqOFyzCCSr9eYPGK2SHJfgCXF_QOmPKog@mail.gmail.com>
 <CAG48ez25=6qrCU51dEAV_ciyU2jvPuRFWfFOAAT22kmeAZccuQ@mail.gmail.com> <CAHk-=wjE_YJ4SFJUasF=tW0jMr6zg+rkRNuNt2hdODPu_LLTVw@mail.gmail.com>
In-Reply-To: <CAHk-=wjE_YJ4SFJUasF=tW0jMr6zg+rkRNuNt2hdODPu_LLTVw@mail.gmail.com>
From:   Jann Horn <jannh@google.com>
Date:   Thu, 30 Apr 2020 05:41:07 +0200
Message-ID: <CAG48ez0yLF4KAK5uMi1_b9woC7NYy0NamYD1jP7BOPJkpKR7Mw@mail.gmail.com>
Subject: Re: [GIT PULL] Please pull proc and exec work for 5.7-rc1
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Bernd Edlinger <bernd.edlinger@hotmail.de>,
        Oleg Nesterov <oleg@redhat.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Waiman Long <longman@redhat.com>,
        Ingo Molnar <mingo@kernel.org>, Will Deacon <will@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Alexey Gladkov <gladkov.alexey@gmail.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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.