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

From: Casey Schaufler <casey@schaufler-ca.com>
To: Stephen Smalley <sds@tycho.nsa.gov>,
	James Morris <jmorris@namei.org>,
	James Morris <james.l.morris@oracle.com>,
	LSM <linux-security-module@vger.kernel.org>,
	LKLM <linux-kernel@vger.kernel.org>
Cc: Paul Moore <pmoore@redhat.com>,
	John Johansen <john.johansen@canonical.com>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	Eric Paris <eparis@redhat.com>, Kees Cook <keescook@chromium.org>,
	Casey Schaufler <casey@schaufler-ca.com>
Subject: Re: [PATCH 6/7 v21] LSM: Switch to lists of hooks
Date: Wed, 11 Mar 2015 11:47:44 -0700	[thread overview]
Message-ID: <55008DD0.3030402@schaufler-ca.com> (raw)
In-Reply-To: <5500708B.3050101@tycho.nsa.gov>

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@schaufler-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.

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