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

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Date:	Wed, 11 Mar 2015 12:42:51 -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 03/09/2015 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.
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