linux-kernel - Re: [PATCH v2 01/24] exec: Move unshare_files to fix posix file locking during exec

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Message-ID: <CAHk-=wh9YvRgb2TsBaJnRM3eARaUp1U-_H-5yMVmSHifC6b-QQ@mail.gmail.com>
Date:   Fri, 20 Nov 2020 15:58:56 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>, criu@...nvz.org,
        bpf <bpf@...r.kernel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Oleg Nesterov <oleg@...hat.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 01/24] exec: Move unshare_files to fix posix file
 locking during exec

On Fri, Nov 20, 2020 at 3:16 PM Eric W. Biederman <ebiederm@...ssion.com> wrote:
>
> @@ -1257,6 +1258,13 @@ int begin_new_exec(struct linux_binprm * bprm)
>         if (retval)
>                 goto out;
>
> +       /* Ensure the files table is not shared. */
> +       retval = unshare_files(&displaced);
> +       if (retval)
> +               goto out;
> +       if (displaced)
> +               put_files_struct(displaced);

It's not obvious from the patch (not enough context), but the new
placement seems to make much more sense - and it's where we do the
de-thread and switch the vm and signals too.

So this does seem to be the much more logical place.

Ack.

      Linus