[PATCH 5/4] Clean up capability.h and capability.c

[Serge E. Hallyn]

Convert macros to functions to let type safety do its thing.  Switch
some functions from ints to more appropriate bool.  Move all forward
declarations together to top of the #ifdef __KERNEL__ section.  Use
kernel-doc format for comments.

Some macros couldn't be converted because they use functions from
security.h which sometimes are extern and sometimes static inline,
and we don't want to #include security.h in capability.h.

Also add a real current_user_ns function (and convert the existing
macro to _current_user_ns() so we can use it in capability.h
without #including cred.h.

Signed-off-by: Serge E. Hallyn <serge.hallyn@xxxxxxxxxxxxx>
---
 include/linux/capability.h |   38 ++++++++++++++++++++++++++------------
 include/linux/cred.h       |    4 +++-
 kernel/capability.c        |   20 ++++++++++++--------
 kernel/cred.c              |    5 +++++
 4 files changed, 46 insertions(+), 21 deletions(-)

diff --git a/include/linux/capability.h b/include/linux/capability.h
index bc0f262..688462f 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -368,6 +368,17 @@ struct cpu_vfs_cap_data {
 
 #ifdef __KERNEL__
 
+struct dentry;
+struct user_namespace;
+
+extern struct user_namespace init_user_ns;
+
+struct user_namespace *current_user_ns(void);
+
+extern const kernel_cap_t __cap_empty_set;
+extern const kernel_cap_t __cap_full_set;
+extern const kernel_cap_t __cap_init_eff_set;
+
 /*
  * Internal kernel functions only
  */
@@ -530,10 +541,6 @@ static inline kernel_cap_t cap_raise_nfsd_set(const kernel_cap_t a,
 			   cap_intersect(permitted, __cap_nfsd_set));
 }
 
-extern const kernel_cap_t __cap_empty_set;
-extern const kernel_cap_t __cap_full_set;
-extern const kernel_cap_t __cap_init_eff_set;
-
 /**
  * has_capability - Determine if a task has a superior capability available
  * @t: The task in question
@@ -560,18 +567,25 @@ extern const kernel_cap_t __cap_init_eff_set;
  * Note that this does not set PF_SUPERPRIV on the task.
  */
 #define has_capability_noaudit(t, cap) \
-	(security_real_capable_noaudit((t), &init_user_ns, (cap)) == 0)
+       (security_real_capable_noaudit((t), &init_user_ns, (cap)) == 0)
 
-struct user_namespace;
-extern struct user_namespace init_user_ns;
-extern int capable(int cap);
-extern int ns_capable(struct user_namespace *ns, int cap);
-extern int task_ns_capable(struct task_struct *t, 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);
 
-#define nsown_capable(cap) (ns_capable(current_user_ns(), (cap)))
+/**
+ * nsown_capable - Check superior capability to one's own user_ns
+ * @cap: The capability in question
+ *
+ * Return true if the current task has the given superior capability
+ * targeted at its own user namespace.
+ */
+static inline bool nsown_capable(int cap)
+{
+	return ns_capable(current_user_ns(), cap);
+}
 
 /* audit system wants to get cap info from files as well */
-struct dentry;
 extern int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps);
 
 #endif /* __KERNEL__ */
diff --git a/include/linux/cred.h b/include/linux/cred.h
index 4aaeab3..9aeeb0b 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -354,9 +354,11 @@ static inline void put_cred(const struct cred *_cred)
 #define current_fsgid() 	(current_cred_xxx(fsgid))
 #define current_cap()		(current_cred_xxx(cap_effective))
 #define current_user()		(current_cred_xxx(user))
-#define current_user_ns()	(current_cred_xxx(user)->user_ns)
+#define _current_user_ns()	(current_cred_xxx(user)->user_ns)
 #define current_security()	(current_cred_xxx(security))
 
+extern struct user_namespace *current_user_ns(void);
+
 #define current_uid_gid(_uid, _gid)		\
 do {						\
 	const struct cred *__cred;		\
diff --git a/kernel/capability.c b/kernel/capability.c
index 916658c..0a3d2c8 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -300,7 +300,7 @@ error:
  * This sets PF_SUPERPRIV on the task if the capability is available on the
  * assumption that it's about to be used.
  */
-int capable(int cap)
+bool capable(int cap)
 {
 	return ns_capable(&init_user_ns, cap);
 }
@@ -317,7 +317,7 @@ EXPORT_SYMBOL(capable);
  * This sets PF_SUPERPRIV on the task if the capability is available on the
  * assumption that it's about to be used.
  */
-int ns_capable(struct user_namespace *ns, int cap)
+bool ns_capable(struct user_namespace *ns, int cap)
 {
 	if (unlikely(!cap_valid(cap))) {
 		printk(KERN_CRIT "capable() called with invalid cap=%u\n", cap);
@@ -326,17 +326,21 @@ int ns_capable(struct user_namespace *ns, int cap)
 
 	if (security_capable(ns, current_cred(), cap) == 0) {
 		current->flags |= PF_SUPERPRIV;
-		return 1;
+		return true;
 	}
-	return 0;
+	return false;
 }
 EXPORT_SYMBOL(ns_capable);
 
-/*
- * does current have capability 'cap' to the user namespace of task
- * 't'.  Return true if it does, false otherwise.
+/**
+ * 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.
  */
-int task_ns_capable(struct task_struct *t, int cap)
+bool task_ns_capable(struct task_struct *t, int cap)
 {
 	return ns_capable(task_cred_xxx(t, user)->user_ns, cap);
 }
diff --git a/kernel/cred.c b/kernel/cred.c
index 3a9d6dd..e447fa2 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -741,6 +741,11 @@ int set_create_files_as(struct cred *new, struct inode *inode)
 }
 EXPORT_SYMBOL(set_create_files_as);
 
+struct user_namespace *current_user_ns(void)
+{
+	return _current_user_ns();
+}
+
 #ifdef CONFIG_DEBUG_CREDENTIALS
 
 bool creds_are_invalid(const struct cred *cred)
-- 
1.7.0.4

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