selinux: Streamline type determination in security_compute_sid

Simplifies the logic for determining the security context type in
security_compute_sid, enhancing readability and efficiency.

Consolidates default type assignment logic next to type transition
checks, removing redundancy and improving code flow.

Signed-off-by: Canfeng Guo <guocanfeng@uniontech.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

Author: Canfeng Guo

security/selinux/ss/services.c

@@ -1804,22 +1804,9 @@ static int security_compute_sid(u32 ssid,
 			newcontext.role = OBJECT_R_VAL;
 	}
 
-	/* Set the type to default values. */
-	if (cladatum && cladatum->default_type == DEFAULT_SOURCE) {
-		newcontext.type = scontext->type;
-	} else if (cladatum && cladatum->default_type == DEFAULT_TARGET) {
-		newcontext.type = tcontext->type;
-	} else {
-		if ((tclass == policydb->process_class) || sock) {
-			/* Use the type of process. */
-			newcontext.type = scontext->type;
-		} else {
-			/* Use the type of the related object. */
-			newcontext.type = tcontext->type;
-		}
-	}
-
-	/* Look for a type transition/member/change rule. */
+	/* Set the type.
+	 * Look for a type transition/member/change rule.
+	 */
 	avkey.source_type = scontext->type;
 	avkey.target_type = tcontext->type;
 	avkey.target_class = tclass;
@@ -1837,9 +1824,24 @@ static int security_compute_sid(u32 ssid,
 		}
 	}
 
+	/* If a permanent rule is found, use the type from
+	 * the type transition/member/change rule. Otherwise,
+	 * set the type to its default values.
+	 */
 	if (avnode) {
-		/* Use the type from the type transition/member/change rule. */
 		newcontext.type = avnode->datum.u.data;
+	} else if (cladatum && cladatum->default_type == DEFAULT_SOURCE) {
+		newcontext.type = scontext->type;
+	} else if (cladatum && cladatum->default_type == DEFAULT_TARGET) {
+		newcontext.type = tcontext->type;
+	} else {
+		if ((tclass == policydb->process_class) || sock) {
+			/* Use the type of process. */
+			newcontext.type = scontext->type;
+		} else {
+			/* Use the type of the related object. */
+			newcontext.type = tcontext->type;
+		}
 	}
 
 	/* if we have a objname this is a file trans check so check those rules */