[PATCH 1/3] libselinux: refactor wrapper in sestatus.c for safe shared memory access

[Christian Göttsche <cgzones@xxxxxxxxxxxxxx>]

Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
---
 libselinux/src/sestatus.c | 35 +++++++++++------------------------
 1 file changed, 11 insertions(+), 24 deletions(-)

diff --git a/libselinux/src/sestatus.c b/libselinux/src/sestatus.c
index 814e86ee..925e6079 100644
--- a/libselinux/src/sestatus.c
+++ b/libselinux/src/sestatus.c
@@ -80,6 +80,14 @@ static inline uint32_t read_sequence(struct selinux_status_t *status)
 	return seqno;
 }
 
+/* sequence must not be changed during references */
+#define sestatus_save_access(name, result)                          \
+	uint32_t _seqno;                                            \
+	do {                                                        \
+		_seqno = read_sequence(selinux_status);             \
+		(result) = selinux_status->name;                    \
+	} while (_seqno != read_sequence(selinux_status))           \
+
 /*
  * selinux_status_updated
  *
@@ -142,7 +150,6 @@ int selinux_status_updated(void)
  */
 int selinux_status_getenforce(void)
 {
-	uint32_t	seqno;
 	uint32_t	enforcing;
 
 	if (selinux_status == NULL) {
@@ -157,13 +164,7 @@ int selinux_status_getenforce(void)
 		return fallback_enforcing;
 	}
 
-	/* sequence must not be changed during references */
-	do {
-		seqno = read_sequence(selinux_status);
-
-		enforcing = selinux_status->enforcing;
-
-	} while (seqno != read_sequence(selinux_status));
+	sestatus_save_access(enforcing, enforcing);
 
 	return enforcing ? 1 : 0;
 }
@@ -179,7 +180,6 @@ int selinux_status_getenforce(void)
  */
 int selinux_status_policyload(void)
 {
-	uint32_t	seqno;
 	uint32_t	policyload;
 
 	if (selinux_status == NULL) {
@@ -194,13 +194,7 @@ int selinux_status_policyload(void)
 		return fallback_policyload;
 	}
 
-	/* sequence must not be changed during references */
-	do {
-		seqno = read_sequence(selinux_status);
-
-		policyload = selinux_status->policyload;
-
-	} while (seqno != read_sequence(selinux_status));
+	sestatus_save_access(policyload, policyload);
 
 	return policyload;
 }
@@ -214,7 +208,6 @@ int selinux_status_policyload(void)
  */
 int selinux_status_deny_unknown(void)
 {
-	uint32_t	seqno;
 	uint32_t	deny_unknown;
 
 	if (selinux_status == NULL) {
@@ -225,13 +218,7 @@ int selinux_status_deny_unknown(void)
 	if (selinux_status == MAP_FAILED)
 		return security_deny_unknown();
 
-	/* sequence must not be changed during references */
-	do {
-		seqno = read_sequence(selinux_status);
-
-		deny_unknown = selinux_status->deny_unknown;
-
-	} while (seqno != read_sequence(selinux_status));
+	sestatus_save_access(deny_unknown, deny_unknown);
 
 	return deny_unknown ? 1 : 0;
 }
-- 
2.28.0