Re: [PATCH 0/4] reST-directive kernel-cmd / include contentent from scripts

[Mauro Carvalho Chehab <mchehab@infradead.org>]

Em Sat, 22 Oct 2016 09:04:21 -0600
Jonathan Corbet <corbet@lwn.net> escreveu:

> On Sat, 22 Oct 2016 08:56:29 -0200
> Mauro Carvalho Chehab <mchehab@infradead.org> wrote:
> 
> > The security implications will be the same if either coded as an
> > "ioctl()" or as "syscall", the scripts should be audited. Actually,
> > if we force the need of a "syscall" for every such script, we have
> > twice the code to audit, as both the Sphinx extension and the perl
> > script will need to audit, increasing the attack surface.  
> 
> Just addressing this one part for the moment.  Clearly I've not explained
> my concern well.
> 
> The kernel-cmd directive makes it possible for *any* RST file to run
> arbitrary shell commands.  I'm not concerned about the scripts we add, I
> hope we can get those right.  I'm worried about what slips in via a tweak
> to some obscure .rst file somewhere.
> 
> A quick check says that 932 commits touched Documentation/ since 4.8.  A
> lot of those did not come from either my tree or yours; *everybody* messes
> around in the docs tree.  People know to look closely at changes to
> makefiles and such; nobody thinks to examine documentation changes for
> such things. I think there are attackers out there who would like the
> opportunity to run commands in the settings where kernels are built; we
> need to think pretty hard before we make that easier to do.
> 
> See what I'm getting at here?

Yes, I see your point, but IMHO, if we add an extra logic at kernel-cmd to
restrict it to run scripts *only* from an specific directory 
(like Documentation/sphinx), then you'll have a better control.
There were only 37 commits there, from you, me and Jani (and, AFAIKT, all
of them were sent to the linux-doc ML for review):

$ git log --pretty=fuller Documentation/sphinx|grep Commit:|sort|uniq -c
     11 Commit:     Jani Nikula <jani.nikula@intel.com>
     10 Commit:     Jonathan Corbet <corbet@lwn.net>
     16 Commit:     Mauro Carvalho Chehab <mchehab@s-opensource.com>

With is, btw, the same rule we have for a Sphinx extension. 

If you thing this isn't enough, we could also add some logic at
checkpatch.pl to check for the usage of Sphinx extensions.

Thanks,
Mauro