Re: [PATCH] kernel: make /proc/kallsyms mode 400 to reduce ease ofattacking

[david]

On Fri, 19 Nov 2010, Linus Torvalds wrote:

> On Fri, Nov 19, 2010 at 11:19 AM, Sarah Sharp
> <sarah.a.sharp@xxxxxxxxxxxxxxx> wrote:
> > .config and dmesg are attached.  The box is running klogd 1.5.5ubuntu3
> > (from Jaunty).  Yes, I know that's old.  I read the bit in the commit
> > about changing the permissions of kallsyms after boot, but if I can't
> > boot that doesn't help.  Perhaps this can be made a configuration
> > option?
>
> It's not worth a config option.
>
> If it actually breaks user-space, I think we should just revert it.

how far back do we need to maintain compatibility with userspace?

Is this something that we can revisit in a few years and lock it down 
then?

David Lang

> It's kind of sad to default to the world-visible thing, but as I
> mentioned in the commit, this is something where a sysadmin or distro
> can trivially just fix it at boot-time too, with just a
>
>   chmod og-r /proc/kallsyms
>
> in your bootup scripts.
>
> And if somebody has taken control of the machine _before_ the bootup
> scripts get to run, you have bigger problems than a /proc/kallsyms
> file.
>
> So I guess I'll revert it.
>
> Thanks for testing and bisecting.
>
>                      Linus
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