[PATCH 2/2] hijack: update task_alloc_security

[Crispin Cowan]

Serge E. Hallyn wrote:
> Quoting Crispin Cowan (crispin at crispincowan.com):
>   
>> Is there to be an LSM hook, so that modules can decide on an arbitrary
>> decision of whether to allow a hijack? So that this "do the right
>> SELinux" thing can be generalized for all LSMs to do the right thing.
>>     
> Currently:
>
> 	1. the permission is granted through ptrace
> 	2. the lsm knows a hijack is going in security_task_alloc()
> 		when task != current
>
> so the lsm has all the information it needs.  But I have no objection
> to a separate security_task_hijack() hook if you find the ptrace hook
> insufficient.
>   
I find that ptrace, specifically CAP_SYS_PTRACE, is overloaded. AppArmor
is having problems because we have to choose between granting
cap_sys_ptrace, or not allowing the process to read /proc/pid/self &
such like. So there, the problem is that we have to grant too much power
to a process to just let it read some /proc stuff about itself.

Here the problem appears to be the other way. cap_sys_ptrace is powerful
enough to mess with other user's processes on the system, but if ptrace
gives you hijack, then that seems to give you the power to control
processes in someone else's namespace.

Crispin

-- 
Crispin Cowan, Ph.D.               http://crispincowan.com/~crispin
CEO, Mercenary Linux		   http://mercenarylinux.com/
	       Itanium. Vista. GPLv3. Complexity at work