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

Stephen Smalley
2015-03-11T16:43:52Z

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.