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: <87r1on1v62.fsf@x220.int.ebiederm.org> <20201120231441.29911-2-ebiederm@xmission.com>
 <20201123175052.GA20279@redhat.com>
In-Reply-To: <20201123175052.GA20279@redhat.com>
From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Mon, 23 Nov 2020 10:25:13 -0800
Message-ID: <CAHk-=wj2OnjWr696z4yzDO9_mF44ND60qBHPvi1i9DBrjdLvUw@mail.gmail.com>
Subject: Re: [PATCH v2 02/24] exec: Simplify unshare_files
To:     Oleg Nesterov <oleg@redhat.com>
Cc:     "Eric W. Biederman" <ebiederm@xmission.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>, criu@openvz.org,
        bpf <bpf@vger.kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        Jann Horn <jann@thejh.net>, Kees Cook <keescook@chromium.org>,
        =?UTF-8?Q?Daniel_P_=2E_Berrang=C3=A9?= <berrange@redhat.com>,
        Jeff Layton <jlayton@redhat.com>,
        Miklos Szeredi <miklos@szeredi.hu>,
        Matthew Wilcox <willy@infradead.org>,
        "J. Bruce Fields" <bfields@fieldses.org>,
        Trond Myklebust <trond.myklebust@hammerspace.com>,
        Chris Wright <chrisw@redhat.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        Andrii Nakryiko <andriin@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@chromium.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Mon, Nov 23, 2020 at 9:52 AM Oleg Nesterov <oleg@redhat.com> wrote:
>
> Can anyone explain why does do_coredump() need unshare_files() at all?

Hmm. It goes back to 2012, and it's placed just before calling
"->core_dump()", so I assume some core dumping function messed with
the file table back when..

I can't see anything like that currently.

The alternative is that core-dumping just keeps the file table around
for a long while, and thus files don't actually close in a timely
manner. So it might not be a "correctness" issue as much as a latency
issue.

             Linus