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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Tue, 10 Jul 2018 18:48:30 -0700
Message-ID: <CA+55aFznwKKy0Vj4Wxe16=2EUmgas_Dcr9QQ1tOJOQOEAVfr+w@mail.gmail.com>
Subject: Re: [PATCH 24/32] vfs: syscall: Add fsopen() to prepare for
 superblock creation [ver #9]
To:     Al Viro <viro@zeniv.linux.org.uk>
Cc:     Andy Lutomirski <luto@amacapital.net>,
        David Howells <dhowells@redhat.com>,
        Linux API <linux-api@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Jann Horn <jannh@google.com>
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On Tue, Jul 10, 2018 at 6:15 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> Umm...  How about "use credentials of opener for everything"?

yeah, we have that for writes in general.

Nobody ever actually follows that rule. They may *think* they do, and
then they call to some helper that does "capability(CAP_SYS_WHATEVAH)"
without even realizing it.

But I'm certainly ok with writes, if it's just filling a buffer.
Preferably a standard buffer we already have, like a seqfile or pipe
(hey, splice!) or whatever.

And then you have that final op to actually "commit" the state. Which
shouldn't be a write (and not the close).

           Linus