[ASM] Fix our legacy encoder benchmarks memory leak

tracer/missing-nullability-files.csv

@@ -297,8 +297,6 @@ src/Datadog.Trace/AppSec/Concurrency/ReaderWriterLock.Framework.cs
 src/Datadog.Trace/AppSec/Waf/IWaf.cs
 src/Datadog.Trace/AppSec/Waf/WafConstants.cs
 src/Datadog.Trace/AppSec/Waf/WafReturnCode.cs
-src/Datadog.Trace/AppSec/WafEncoding/Obj.cs
-src/Datadog.Trace/AppSec/WafEncoding/ObjType.cs
 src/Datadog.Trace/Ci/Agent/ApmAgentWriter.cs
 src/Datadog.Trace/Ci/Agent/CIVisibilityProtocolWriter.cs
 src/Datadog.Trace/Ci/Agent/CIWriterFileSender.cs

tracer/src/Datadog.Trace/AppSec/Waf/Context.cs

@@ -25,7 +25,7 @@ internal class Context : IContext
 
         private readonly Waf _waf;
 
-        private readonly List<IEncodeResult> _argCache;
+        private readonly List<IEncodeResult> _encodeResults;
         private readonly Stopwatch _stopwatch;
         private readonly WafLibraryInvoker _wafLibraryInvoker;
         private readonly IEncoder _encoder;
@@ -41,7 +41,7 @@ private Context(IntPtr contextHandle, Waf waf, WafLibraryInvoker wafLibraryInvok
             _wafLibraryInvoker = wafLibraryInvoker;
             _encoder = encoder;
             _stopwatch = new Stopwatch();
-            _argCache = new(64);
+            _encodeResults = new(64);
         }
 
         ~Context() => Dispose(false);
@@ -64,7 +64,7 @@ private Context(IntPtr contextHandle, Waf waf, WafLibraryInvoker wafLibraryInvok
         public IResult? RunWithEphemeral(IDictionary<string, object> ephemeralAddressData, ulong timeoutMicroSeconds)
             => RunInternal(null, ephemeralAddressData, timeoutMicroSeconds);
 
-        private IResult? RunInternal(IDictionary<string, object>? persistentAddressData, IDictionary<string, object>? ephemeralAddressData, ulong timeoutMicroSeconds)
+        private unsafe IResult? RunInternal(IDictionary<string, object>? persistentAddressData, IDictionary<string, object>? ephemeralAddressData, ulong timeoutMicroSeconds)
         {
             if (_disposed)
             {
@@ -100,29 +100,35 @@ private Context(IntPtr contextHandle, Waf waf, WafLibraryInvoker wafLibraryInvok
                 // Calling _encoder.Encode(null) results in a null object that will cause the WAF to error
                 // The WAF can be called with an empty dictionary (though we should avoid doing this).
 
-                var pwPersistentArgs = IntPtr.Zero;
-                if (persistentAddressData != null)
+                DdwafObjectStruct pwPersistentArgs = default;
+                DdwafObjectStruct pwEphemeralArgsValue = default;
+
+                if (persistentAddressData is not null)
                 {
                     var persistentArgs = _encoder.Encode(persistentAddressData, applySafetyLimits: true);
-                    pwPersistentArgs = persistentArgs.Result;
-                    _argCache.Add(persistentArgs);
+                    pwPersistentArgs = persistentArgs.ResultDdwafObject;
+                    _encodeResults.Add(persistentArgs);
                 }
 
                 // pwEphemeralArgs follow a different lifecycle and should be disposed immediately
-                using var ephemeralArgs =
-                    ephemeralAddressData is { Count: > 0 }
-                    ? _encoder.Encode(ephemeralAddressData, applySafetyLimits: true)
-                    : null;
-                var pwEphemeralArgs = ephemeralArgs?.Result ?? IntPtr.Zero;
+                using var ephemeralArgs = ephemeralAddressData is { Count: > 0 }
+                                              ? _encoder.Encode(ephemeralAddressData, applySafetyLimits: true)
+                                              : null;
 
-                if (pwPersistentArgs == IntPtr.Zero && pwEphemeralArgs == IntPtr.Zero)
+                if (persistentAddressData is null && ephemeralArgs is null)
                 {
                     Log.Error("Both pwPersistentArgs and pwEphemeralArgs are null");
                     return null;
                 }
 
+                if (ephemeralArgs is not null)
+                {
+                    // WARNING: Don't use ref here, we need to make a copy because ephemeralArgs is on the heap
+                    pwEphemeralArgsValue = ephemeralArgs.ResultDdwafObject;
+                }
+
                 // WARNING: DO NOT DISPOSE pwPersistentArgs until the end of this class's lifecycle, i.e in the dispose. Otherwise waf might crash with fatal exception.
-                code = _waf.Run(_contextHandle, pwPersistentArgs, pwEphemeralArgs,  ref retNative, timeoutMicroSeconds);
+                code = _waf.Run(_contextHandle, persistentAddressData != null ? &pwPersistentArgs : null, ephemeralArgs != null ? &pwEphemeralArgsValue : null, ref retNative, timeoutMicroSeconds);
             }
 
             _stopwatch.Stop();
@@ -151,9 +157,9 @@ public void Dispose(bool disposing)
             _disposed = true;
 
             // WARNING do not move this above, this should only be disposed in the end of the context's life
-            foreach (var arg in _argCache)
+            foreach (var encodeResult in _encodeResults)
             {
-                arg.Dispose();
+                encodeResult.Dispose();
             }
 
             lock (_stopwatch)

tracer/src/Datadog.Trace/AppSec/Waf/IWaf.cs

@@ -19,7 +19,7 @@ internal interface IWaf : IDisposable
 
         public IContext CreateContext();
 
-        internal WafReturnCode Run(IntPtr contextHandle, IntPtr rawPersistentData, IntPtr rawEphemeralData, ref DdwafResultStruct retNative, ulong timeoutMicroSeconds);
+        internal unsafe WafReturnCode Run(IntPtr contextHandle, DdwafObjectStruct* rawPersistentData, DdwafObjectStruct* rawEphemeralData, ref DdwafResultStruct retNative, ulong timeoutMicroSeconds);
 
         UpdateResult UpdateWafFromConfigurationStatus(ConfigurationStatus configurationStatus);
     }

tracer/src/Datadog.Trace/AppSec/Waf/Initialization/WafConfigurator.cs

@@ -112,9 +112,9 @@ private static void LogRuleDetailsIfDebugEnabled(JToken root)
             return root;
         }
 
-        internal InitResult Configure(IntPtr rulesObj, IEncoder encoder, DdwafConfigStruct configStruct, ref DdwafObjectStruct diagnostics, string? rulesFile)
+        internal InitResult Configure(ref DdwafObjectStruct rulesObj, IEncoder encoder, DdwafConfigStruct configStruct, ref DdwafObjectStruct diagnostics, string? rulesFile)
         {
-            var wafHandle = _wafLibraryInvoker.Init(rulesObj, ref configStruct, ref diagnostics);
+            var wafHandle = _wafLibraryInvoker.Init(ref rulesObj, ref configStruct, ref diagnostics);
             if (wafHandle == IntPtr.Zero)
             {
                 Log.Warning("DDAS-0005-00: WAF initialization failed.");