linux-kernel - Re: [PATCH man-pages v2 2/2] openat2.2: document new openat2(2) syscall

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Date:   Mon, 30 Mar 2020 11:08:12 +0200
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:     Aleksa Sarai <cyphar@...har.com>, Al Viro <viro@...iv.linux.org.uk>
Cc:     mtk.manpages@...il.com, Christian Brauner <christian@...uner.io>,
        Aleksa Sarai <asarai@...e.de>, linux-man@...r.kernel.org,
        linux-api@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH man-pages v2 2/2] openat2.2: document new openat2(2)
 syscall

Hello Aleksa,

On 2/2/20 4:19 PM, Aleksa Sarai wrote:
> Rather than trying to merge the new syscall documentation into open.2
> (which would probably result in the man-page being incomprehensible),
> instead the new syscall gets its own dedicated page with links between
> open(2) and openat2(2) to avoid duplicating information such as the list
> of O_* flags or common errors.
> 
> In addition to describing all of the key flags, information about the
> extensibility design is provided so that users can better understand why
> they need to pass sizeof(struct open_how) and how their programs will
> work across kernels. After some discussions with David Laight, I also
> included explicit instructions to zero the structure to avoid issues
> when recompiling with new headers.>
> Signed-off-by: Aleksa Sarai <cyphar@...har.com>

I'm just editing this page, and have a question on one piece.

> +Unlike
> +.BR openat (2),
> +it is an error to provide
> +.BR openat2 ()
> +with a
> +.I mode
> +which contains bits other than
> +.IR 0777 ,

This piece appears not to be true, both from my reading of the
source code, and from testing (i.e., I wrote a a small program that
successfully called openat2() and created a file that had the
set-UID, set-GID, and sticky bits set).

Is this a bug in the implementation or a bug in the manual page text?

Thanks,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/