linux-kernel - Re: [PATCH] vfs: Add PERM_* symbolic helpers for common file mode/permissions

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Date:   Mon, 27 Nov 2017 11:21:28 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Rik van Riel <riel@...hat.com>,
        Daniel Gruss <daniel.gruss@...k.tugraz.at>,
        Hugh Dickins <hughd@...gle.com>,
        Kees Cook <keescook@...gle.com>, linux-mm <linux-mm@...ck.org>,
        michael.schwarz@...k.tugraz.at, moritz.lipp@...k.tugraz.at,
        richard.fellner@...dent.tugraz.at
Subject: Re: [PATCH] vfs: Add PERM_* symbolic helpers for common file mode/permissions

On Mon, Nov 27, 2017 at 2:06 AM, Ingo Molnar <mingo@...nel.org> wrote:
>
>
> +/*
> + * Human readable symbolic definitions for common
> + * file permissions:
> + */
> +#define PERM_r________ 0400
> +#define PERM_r__r_____ 0440
> +#define PERM_r__r__r__ 0444

I'm not a fan. Particularly as you have a very random set of
permissions (rx and wx? Not very common), but also because it's just
not that legible.

I've argued several times that we shouldn't use the defines at all.
The octal format isn't any less legible than any #define I've ever
seen, and is generally _more_ legible.

What's wrong with just using 0400 for "read by user"?

                Linus