Comment the locking mechanisms in ContextInfoManager

[lttng-ust.git] / liblttng-ust-java-agent / java / lttng-ust-agent-common / org / lttng / ust / agent / context / ContextInfoManager.java

diff --git a/liblttng-ust-java-agent/java/lttng-ust-agent-common/org/lttng/ust/agent/context/ContextInfoManager.java b/liblttng-ust-java-agent/java/lttng-ust-agent-common/org/lttng/ust/agent/context/ContextInfoManager.java
index c3999b5d83883637be881352e9359a898b7fbcee..7a8c80e9a83d6040f1ed630b2932870e65f4eb66 100644 (file)
--- a/liblttng-ust-java-agent/java/lttng-ust-agent-common/org/lttng/ust/agent/context/ContextInfoManager.java
+++ b/liblttng-ust-java-agent/java/lttng-ust-agent-common/org/lttng/ust/agent/context/ContextInfoManager.java
@@ -21,6 +21,8 @@ import java.io.IOException;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 /**
  * The singleton manager of {@link IContextInfoRetriever} objects.
@@ -31,11 +33,17 @@ public final class ContextInfoManager {
 
        private static final String SHARED_LIBRARY_NAME = "lttng-ust-context-jni";
 
+       private static final Pattern VALID_CONTEXT_NAME_PATTERN = Pattern.compile("^[a-zA-Z0-9_\\.]+$");
+
        private static ContextInfoManager instance;
 
        private final Map<String, IContextInfoRetriever> contextInfoRetrievers = new ConcurrentHashMap<String, IContextInfoRetriever>();
        private final Map<String, Long> contextInforRetrieverRefs = new HashMap<String, Long>();
 
+       /**
+        * Lock used to keep the two maps above in sync when retrievers are
+        * registered or unregistered.
+        */
        private final Object retrieverLock = new Object();
 
        /** Singleton class, constructor should not be accessed directly */
@@ -95,6 +103,10 @@ public final class ContextInfoManager {
         */
        public boolean registerContextInfoRetriever(String retrieverName, IContextInfoRetriever contextInfoRetriever) {
                synchronized (retrieverLock) {
+                       if (!validateRetrieverName(retrieverName)) {
+                               return false;
+                       }
+
                        if (contextInfoRetrievers.containsKey(retrieverName)) {
                                /*
                                 * There is already a retriever registered with that name,
@@ -155,6 +167,33 @@ public final class ContextInfoManager {
         *         was none
         */
        public IContextInfoRetriever getContextInfoRetriever(String retrieverName) {
+               /*
+                * Note that this method does not take the retrieverLock, it lets
+                * concurrent threads access the ConcurrentHashMap directly.
+                *
+                * It's fine for a get() to happen during a registration or
+                * unregistration, it's first-come-first-serve.
+                */
                return contextInfoRetrievers.get(retrieverName);
        }
+
+       /**
+        * Validate that the given retriever name contains only the allowed
+        * characters, which are alphanumerical characters, period "." and
+        * underscore "_". The name must also not start with a number.
+        */
+       private static boolean validateRetrieverName(String contextName) {
+               if (contextName.isEmpty()) {
+                       return false;
+               }
+
+               /* First character must not be a number */
+               if (Character.isDigit(contextName.charAt(0))) {
+                       return false;
+               }
+
+               /* Validate the other characters of the string */
+               Matcher matcher = VALID_CONTEXT_NAME_PATTERN.matcher(contextName);
+               return matcher.matches();
+       }
 }