linux-kernel - Re: string_escape_mem ESCAPE

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Date:	Thu, 23 Jul 2015 13:36:58 -0700
From:	Kees Cook <keescook@...gle.com>
To:	Andy Shevchenko <andriy.shevchenko@...ux.intel.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, 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 ";

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

>>  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. :)

Thanks!

-Kees

-- 
Kees Cook
Chrome OS Security
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