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

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Date:   Tue, 28 Nov 2017 11:54:58 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.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


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> 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"?

Yeah, the octal format isn't all that bad - at least relative to the symbolic 
obfuscation defines.

Thanks,

	Ingo