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

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Date:	Mon, 7 Jan 2013 02:41:27 +0100
From:	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:	Kees Cook <keescook@...omium.org>
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 9:24 PM, Kees Cook <keescook@...omium.org> wrote:
> 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>

Thanks Kees!



-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/
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