linux-kernel - Re: string_escape_mem ESCAPE

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Message-ID: <1437684619.29746.54.camel@linux.intel.com>
Date:	Thu, 23 Jul 2015 23:50:19 +0300
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Kees Cook <keescook@...gle.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Joe Perches <joe@...ches.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: string_escape_mem ESCAPE_SPACE

On Thu, 2015-07-23 at 13:36 -0700, Kees Cook wrote:
> On Thu, Jul 23, 2015 at 1:27 PM, Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com> wrote:
> > On Thu, 2015-07-23 at 12:59 -0700, Kees Cook wrote:
> > > Hi,
> > > 
> > > I'm curious why ESCAPE_SPACE doesn't escape spaces (0x20)?
> > 
> > Space is a printable character.
> > You perhaps wants something like ESCAPE_SPACE | ESCAPE_HEX.
> 
> Yeah, I can get the effect I want with:
> 
> flags = ESCAPE_SPACE | ESCAPE_SPECIAL | ESCAPE_NULL | ESCAPE_HEX;
> esc = "\f\n\r\t\v\\\a\e\0 ";

esc can't contain '\0' in the middle.

So, you would like to convert only space to hex and leave everything
else printable as is?

> 
> This isn't reachable via kasprintf, though (it always has a NULL 
> esc).
> I will consider some options and send patches.

Before doing this, describe your use case in detail, please.

> 
> > >  That is
> > > surprising to me, especially since things like isspace() include
> > > 0x20.
> > 
> > Moreover, there are test cases in test-string_helpers.c module and 
> > they
> > are based on the real use cases (before helpers were introduced and
> > users were converted). So, there is no user which expects hex 
> > conversio
> > n of the printable character if not asked explicitly.
> 
> Yeah, I saw it was testing for space to be excluded. I guess I just
> think the name "ESCAPE_SPACE" is misleading. :)

For sake of name shortness I suppose. The idea is to escape *special*
spaces by this.

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy
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