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SubjectRe: [PATCH] kernel: make /proc/kallsyms mode 400 to reduce ease of attacking
On 11/29/2010 10:04 AM, Ingo Molnar wrote:
>
> * Sarah Sharp <sarah.a.sharp@linux.intel.com> wrote:
>
>> On Fri, Nov 26, 2010 at 08:48:09AM +0100, Ingo Molnar wrote:
>>>
>>> * Linus Torvalds <torvalds@linux-foundation.org> wrote:
>>>
>>>> On Fri, Nov 19, 2010 at 11:19 AM, Sarah Sharp
>>>> <sarah.a.sharp@linux.intel.com> 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.
>>>
>>> Sarah,
>>>
>>> Does your system boot fine if we make /proc/kallsyms simply an empty file to
>>> unprivileged users? Something like the (untested ...) patch below.
>>
>> Yes, that works. The system boots as normal. `cat /proc/kallsyms`
>> returns an empty file, and `sudo cat /proc/kallsyms` does not.
>
> Great! Marcus, mind respinning your patch with that approach?
>

Can we please not use CAP_SYS_ADMIN for this? Relying on CAP_SYS_ADMIN
is worse than anything else -- it is a fixed policy hardcoded in the
kernel, with no ability for the system owner to delegate the policy
outward, e.g. by adding group read permission and/or chgrp the file.

Delegating CAP_SYS_ADMIN, of course, otherwise known as "everything", is
worse than anything...

-hpa


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