linux-kernel - Re: [PATCH 1/9] Known exploit detection

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Date:	Mon, 16 Dec 2013 00:17:55 -0500
From:	Sasha Levin <sasha.levin@...cle.com>
To:	vegard.nossum@...cle.com, linux-kernel@...r.kernel.org
CC:	Tommi Rantala <tt.rantala@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andy Lutomirski <luto@...capital.net>,
	Kees Cook <keescook@...omium.org>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Alan Cox <alan@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jason Wang <jasowang@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	James Morris <james.l.morris@...cle.com>
Subject: Re: [PATCH 1/9] Known exploit detection

Hi Vegard,

On 12/12/2013 11:52 AM, vegard.nossum@...cle.com wrote:
 > +#ifdef CONFIG_EXPLOIT_DETECTION
 > +extern void _exploit(const char *id);

So right now the on/off switch is a kernel config option. I suggest we should add another
dynamic switch (maybe in the form of jump labels) to add an additional level of control:

  - It will allow having an opt-in option. Right now users are forced into
having this feature if the distro maintainers enable it.
	- Which means that distro maintainers are less likely to enable it.

  - If the SHTF and there's something wrong we would want a way to disable it
without having to re-compile the kernel.


<bikeshedding>
Also,

Maybe in the future we could enable/disable specific exploits based on severity or certainty
(how likely that this specific activity is an exploit attempt).

</bikeshedding>

On 12/12/2013 11:52 AM, vegard.nossum@...cle.com wrote:
> +#define exploit_on(cond, id) \
> +	do { \
> +		if (unlikely(cond)) \
> +			_exploit(id); \
> +	} while (0)

What if we make exploit_on() something like this:

	#define exploit_on(cond, id) ({			\
		int __ret_exploit_on = !!(cond);	\
		if (unlikely(__ret_exploit_on))		\
			_exploit(id);			\
		unlikely(__ret_exploit_on);		\
	})

That way we can use it within if() conditionals similar to WARN_ON:

	if (exploit_on(srclen > HFS_NAMELEN, "CVE-2011-4330"))
		srclen = HFS_NAMELEN;



Thanks,
Sasha
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