linux-kernel - Re: [PATCH 6/7 v21] LSM: Switch to lists of hooks

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Date:	Wed, 11 Mar 2015 15:24:42 -0400
From:	Stephen Smalley <sds@...ho.nsa.gov>
To:	Casey Schaufler <casey@...aufler-ca.com>,
	James Morris <jmorris@...ei.org>,
	James Morris <james.l.morris@...cle.com>,
	LSM <linux-security-module@...r.kernel.org>,
	LKLM <linux-kernel@...r.kernel.org>
CC:	Paul Moore <pmoore@...hat.com>,
	John Johansen <john.johansen@...onical.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	Eric Paris <eparis@...hat.com>,
	Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH 6/7 v21] LSM: Switch to lists of hooks

On 03/11/2015 02:47 PM, Casey Schaufler wrote:
> On 3/11/2015 9:42 AM, Stephen Smalley wrote:
>> On 03/09/2015 09:20 PM, Casey Schaufler wrote:
>>> Subject: [PATCH 6/7 v21] LSM: Switch to lists of hooks
>>>
>>> Instead of using a vector of security operations
>>> with explicit, special case stacking of the capability
>>> and yama hooks use lists of hooks with capability and
>>> yama hooks included as appropriate. 
>>>
>>> The security_operations structure is no longer required.
>>> Instead, there is a union of the function pointers that
>>> allows all the hooks lists to use a common mechanism for
>>> list management while retaining typing. Each module
>>> supplies an array describing the hooks it provides instead
>>> of a sparsely populated security_operations structure.
>>> The description includes the element that gets put on
>>> the hook list, avoiding the issues surrounding individual
>>> element allocation.
>>>  
>>> The method for registering security modules is changed to
>>> reflect the information available. The method for removing
>>> a module, currently only used by SELinux, has also changed.
>>> It should be generic now, however if there are potential
>>> race conditions based on ordering of hook removal that needs
>>> to be addressed by the calling module.
>>>
>>> The security hooks are called from the lists and the first
>>> failure is returned.
>>>  
>>> Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
>>>
>>> --- 
>>> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
>>> index 0c45f08..3fd8610 100644
>>> --- a/security/selinux/hooks.c
>>> +++ b/security/selinux/hooks.c
>>> @@ -2008,24 +2002,12 @@ static int selinux_ptrace_access_check(struct task_struct *child,
>>>  
>>>  static int selinux_ptrace_traceme(struct task_struct *parent)
>>>  {
>>> -	int rc;
>>> -
>>> -	rc = cap_ptrace_traceme(parent);
>>> -	if (rc)
>>> -		return rc;
>>> -
>>>  	return task_has_perm(parent, current, PROCESS__PTRACE);
>>>  }
>>>  
>>>  static int selinux_capget(struct task_struct *target, kernel_cap_t *effective,
>>>  			  kernel_cap_t *inheritable, kernel_cap_t *permitted)
>>>  {
>>> -	int error;
>>> -
>>> -	error = current_has_perm(target, PROCESS__GETCAP);
>>> -	if (error)
>>> -		return error;
>>> -
>>>  	return cap_capget(target, effective, inheritable, permitted);
>> Deleted the wrong code here.
>>
>>>  }
>> And failed to delete the cap_capset() call from selinux_capset(), and
>> the cap_capable() call from selinux_capable(), so we're calling that
>> code twice after the patch.
> 
> So I see. It was right in v19, but wrong in v20. I'll have an update quickly.

Also looks like there is a residual cap_bprm_secureexec() call in
security/apparmor/domain.c.


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