apparmor: make __begin_current_label_crit_section() indicate whether put is needed

Same as aa_get_newest_cred_label_condref().

This avoids a bunch of work overall and allows the compiler to note when no
clean up is necessary, allowing for tail calls.

This in particular happens in apparmor_file_permission(), which manages to
tail call aa_file_perm() 105 bytes in (vs a regular call 112 bytes in
followed by branches to figure out if clean up is needed).

Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>

1 files changed, 15 insertions, 6 deletions

diff --git a/security/apparmor/include/cred.h b/security/apparmor/include/cred.h
index 674af3175905..de6ec4969598 100644
--- a/security/apparmor/include/cred.h
+++ b/security/apparmor/include/cred.h
@@ -114,7 +114,12 @@ static inline struct aa_label *aa_get_current_label(void)
 	return aa_get_label(l);
 }
 
-#define __end_current_label_crit_section(X) end_current_label_crit_section(X)
+static inline void __end_current_label_crit_section(struct aa_label *label,
+						    bool needput)
+{
+	if (unlikely(needput))
+		aa_put_label(label);
+}
 
 /**
  * end_current_label_crit_section - put a reference found with begin_current_label..
@@ -142,13 +147,16 @@ static inline void end_current_label_crit_section(struct aa_label *label)
  * critical section between __begin_current_label_crit_section() ..
  * __end_current_label_crit_section()
  */
-static inline struct aa_label *__begin_current_label_crit_section(void)
+static inline struct aa_label *__begin_current_label_crit_section(bool *needput)
 {
 	struct aa_label *label = aa_current_raw_label();
 
-	if (label_is_stale(label))
-		label = aa_get_newest_label(label);
+	if (label_is_stale(label)) {
+		*needput = true;
+		return aa_get_newest_label(label);
+	}
 
+	*needput = false;
 	return label;
 }
 
@@ -184,10 +192,11 @@ static inline struct aa_ns *aa_get_current_ns(void)
 {
 	struct aa_label *label;
 	struct aa_ns *ns;
+	bool needput;
 
-	label  = __begin_current_label_crit_section();
+	label  = __begin_current_label_crit_section(&needput);
 	ns = aa_get_ns(labels_ns(label));
-	__end_current_label_crit_section(label);
+	__end_current_label_crit_section(label, needput);
 
 	return ns;
 }