capability: Remove unused has_capability

The vanilla has_capability() function has been unused since 2018's
commit dcb569c ("Smack: ptrace capability use fixes")

Remove it.

Fixup a comment in security/commoncap.c that referenced it.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Reviewed-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Serge Hallyn <sergeh@kernel.org>

include/linux/capability.h

@@ -139,7 +139,6 @@ static inline kernel_cap_t cap_raise_nfsd_set(const kernel_cap_t a,
 }
 
 #ifdef CONFIG_MULTIUSER
-extern bool has_capability(struct task_struct *t, int cap);
 extern bool has_ns_capability(struct task_struct *t,
 			      struct user_namespace *ns, int cap);
 extern bool has_capability_noaudit(struct task_struct *t, int cap);
@@ -150,10 +149,6 @@ extern bool ns_capable(struct user_namespace *ns, int cap);
 extern bool ns_capable_noaudit(struct user_namespace *ns, int cap);
 extern bool ns_capable_setid(struct user_namespace *ns, int cap);
 #else
-static inline bool has_capability(struct task_struct *t, int cap)
-{
-	return true;
-}
 static inline bool has_ns_capability(struct task_struct *t,
 			      struct user_namespace *ns, int cap)
 {

kernel/capability.c

@@ -285,22 +285,6 @@ bool has_ns_capability(struct task_struct *t,
 	return (ret == 0);
 }
 
-/**
- * has_capability - Does a task have a capability in init_user_ns
- * @t: The task in question
- * @cap: The capability to be tested for
- *
- * Return true if the specified task has the given superior capability
- * currently in effect to the initial user namespace, false if not.
- *
- * Note that this does not set PF_SUPERPRIV on the task.
- */
-bool has_capability(struct task_struct *t, int cap)
-{
-	return has_ns_capability(t, &init_user_ns, cap);
-}
-EXPORT_SYMBOL(has_capability);
-
 /**
  * has_ns_capability_noaudit - Does a task have a capability (unaudited)
  * in a specific user ns.

security/commoncap.c

@@ -115,10 +115,11 @@ static inline int cap_capable_helper(const struct cred *cred,
  * Determine whether the nominated task has the specified capability amongst
  * its effective set, returning 0 if it does, -ve if it does not.
  *
- * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
- * and has_capability() functions.  That is, it has the reverse semantics:
- * cap_has_capability() returns 0 when a task has a capability, but the
- * kernel's capable() and has_capability() returns 1 for this case.
+ * NOTE WELL: cap_capable() has reverse semantics to the capable() call
+ * and friends. That is cap_capable() returns an int 0 when a task has
+ * a capability, while the kernel's capable(), has_ns_capability(),
+ * has_ns_capability_noaudit(), and has_capability_noaudit() return a
+ * bool true (1) for this case.
  */
 int cap_capable(const struct cred *cred, struct user_namespace *target_ns,
 		int cap, unsigned int opts)