capabilities: remove task_ns_* functions

task_ in the front of a function, in the security subsystem anyway, means
to me at least, that we are operating with that task as the subject of the
security decision.  In this case what it means is that we are using current as
the subject but we use the task to get the right namespace.  Who in the world
would ever realize that's what task_ns_capability means just by the name?  This
patch eliminates the task_ns functions entirely and uses the has_ns_capability
function instead.  This means we explicitly open code the ns in question in
the caller.  I think it makes the caller a LOT more clear what is going on.
Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Serge E. Hallyn <serge.hallyn@canonical.com>

include/linux/capability.h

@@ -547,7 +547,6 @@ extern bool has_ns_capability_noaudit(struct task_struct *t,
 				      struct user_namespace *ns, int cap);
 extern bool capable(int cap);
 extern bool ns_capable(struct user_namespace *ns, int cap);
-extern bool task_ns_capable(struct task_struct *t, int cap);
 extern bool nsown_capable(int cap);
 
 /* audit system wants to get cap info from files as well */

include/linux/cred.h

@@ -359,9 +359,11 @@ static inline void put_cred(const struct cred *_cred)
 
 #ifdef CONFIG_USER_NS
 #define current_user_ns()	(current_cred_xxx(user_ns))
+#define task_user_ns(task)	(task_cred_xxx((task), user_ns))
 #else
 extern struct user_namespace init_user_ns;
 #define current_user_ns()	(&init_user_ns)
+#define task_user_ns(task)	(&init_user_ns)
 #endif
 
 

kernel/capability.c

@@ -408,20 +408,6 @@ bool capable(int cap)
 }
 EXPORT_SYMBOL(capable);
 
-/**
- * task_ns_capable - Determine whether current task has a superior
- * capability targeted at a specific task's user namespace.
- * @t: The task whose user namespace is targeted.
- * @cap: The capability in question.
- *
- *  Return true if it does, false otherwise.
- */
-bool task_ns_capable(struct task_struct *t, int cap)
-{
-	return ns_capable(task_cred_xxx(t, user)->user_ns, cap);
-}
-EXPORT_SYMBOL(task_ns_capable);
-
 /**
  * nsown_capable - Check superior capability to one's own user_ns
  * @cap: The capability in question

kernel/ptrace.c

@@ -196,7 +196,7 @@ int __ptrace_may_access(struct task_struct *task, unsigned int mode)
 	smp_rmb();
 	if (task->mm)
 		dumpable = get_dumpable(task->mm);
-	if (!dumpable && !task_ns_capable(task, CAP_SYS_PTRACE))
+	if (!dumpable && !ns_capable(task_user_ns(task), CAP_SYS_PTRACE))
 		return -EPERM;
 
 	return security_ptrace_access_check(task, mode);
@@ -266,7 +266,7 @@ static int ptrace_attach(struct task_struct *task, long request,
 	task->ptrace = PT_PTRACED;
 	if (seize)
 		task->ptrace |= PT_SEIZED;
-	if (task_ns_capable(task, CAP_SYS_PTRACE))
+	if (ns_capable(task_user_ns(task), CAP_SYS_PTRACE))
 		task->ptrace |= PT_PTRACE_CAP;
 
 	__ptrace_link(task, current);

kernel/sched.c

@@ -5409,7 +5409,7 @@ long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
 		goto out_free_cpus_allowed;
 	}
 	retval = -EPERM;
-	if (!check_same_owner(p) && !task_ns_capable(p, CAP_SYS_NICE))
+	if (!check_same_owner(p) && !ns_capable(task_user_ns(p), CAP_SYS_NICE))
 		goto out_unlock;
 
 	retval = security_task_setscheduler(p);