linux-kernel - Re: [PATCH v2 02/24] exec: Simplify unshare

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Date:   Mon, 23 Nov 2020 18:50:53 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        criu@...nvz.org, bpf@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Jann Horn <jann@...jh.net>, Kees Cook <keescook@...omium.org>,
        Daniel P . Berrangé <berrange@...hat.com>,
        Jeff Layton <jlayton@...hat.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        Matthew Wilcox <willy@...radead.org>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Chris Wright <chrisw@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>
Subject: Re: [PATCH v2 02/24] exec: Simplify unshare_files

I'll try to actually read this series tomorrow but I see nothing wrong
after the quick glance.

Just one off-topic question,

On 11/20, Eric W. Biederman wrote:
>
> --- a/fs/coredump.c
> +++ b/fs/coredump.c
> @@ -585,7 +585,6 @@ void do_coredump(const kernel_siginfo_t *siginfo)
>  	int ispipe;
>  	size_t *argv = NULL;
>  	int argc = 0;
> -	struct files_struct *displaced;
>  	/* require nonrelative corefile path and be extra careful */
>  	bool need_suid_safe = false;
>  	bool core_dumped = false;
> @@ -791,11 +790,9 @@ void do_coredump(const kernel_siginfo_t *siginfo)
>  	}
>
>  	/* get us an unshared descriptor table; almost always a no-op */
> -	retval = unshare_files(&displaced);
> +	retval = unshare_files();

Can anyone explain why does do_coredump() need unshare_files() at all?

Oleg.