linux-kernel - Re: [PATCH 1/4] module: add syscall to load module from fd

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Date:	Sun, 6 Jan 2013 13:24:03 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Michael Kerrisk <mtk.manpages@...il.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	"H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Lucas De Marchi <lucas.demarchi@...fusion.mobi>,
	jonathon@...masters.org, linux-man@...r.kernel.org
Subject: Re: [PATCH 1/4] module: add syscall to load module from fd

On Sun, Jan 6, 2013 at 11:59 AM, Michael Kerrisk (man-pages)
<mtk.manpages@...il.com> wrote:
> Hi Rusty, (and Lucas, and Kees)
>
> On Thu, Jan 3, 2013 at 1:12 AM, Rusty Russell <rusty@...tcorp.com.au> wrote:
>> Michael Kerrisk <mtk.manpages@...il.com> writes:
>>> Hi Rusty,
>>
>> Hi Michael,
>>
>>> The description here is rather thin. Could you supply a sentence or
>>> two for each of MODULE_INIT_IGNORE_MODVERSIONS and
>>> MODULE_INIT_IGNORE_VERMAGIC that would be suitable for the manual
>>> page?
>>>
>>> Thanks,
>>
>> There are one or two safety checks built into a module, which are
>> checked to match the kernel on module load.  The first is a "vermagic"
>> string containing the kernel version number and prominent features (such
>> as CPU type).  If the module was built with CONFIG_MODVERSIONS set, a
>> version hash is recorded for each symbol the module uses based on the
>> types it refers to: in this case, the kernel version number within the
>> "vermagic" string is ignored, as the symbol version hashes are assumed
>> to be sufficiently reliable.
>>
>> Using the MODULE_INIT_IGNORE_VERMAGIC flag indicates that the vermagic
>> is to be ignored, and the MODULE_INIT_IGNORE_MODVERSIONS flag indicates
>> that the version hashes are to be ignored.  If the kernel is built to
>> permit such forced loading (ie. CONFIG_MODULE_FORCE_LOAD is set) then
>> loading will continue, otherwise it will fail with ENOEXEC as expected
>> for malformed modules.
>>
>> Hope that is more usable?
>
> Yes, that helps. I did some reworking of that text. Hopefully, I did
> not introduce any errors.
>
> Below is the text that is proposed to document finit_module() in the
> man pages. I'd appreciate any review (Kees, Lucas, Rusty?)

Looks good to me!

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

--
Kees Cook
Chrome OS Security
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