Re: more thoughts on a new jail() system call

[David Wagner]

Albert D. Cahalan wrote:
>>> sys_olduname) - P
>>
>> I'd argue that this should be restricted, on general
>> principles.  (General principle: A jailed process shouldn't
>> be able to learn anything about the host it's running on.)
>
>Learning this info is easy enough without a syscall.
>You only cause trouble for legit usage.

Ok.  To be clear, I consider this minor and probably
unimportant for security, hence just allowing this is
probably reasonable.

That said, is it really true that you can learn the
hostname and the like without a syscall?  How?

>No, sys_getcwd will return info based on your current root.
>After chroot and all, your "/" is the top of your jail.

Ahh, I feel stupid for overlooking that.  You're
absolutely right.  Thanks for the correction.