Ruby: Prevent flow into self in trackBlock

Author: hvitved

ruby/ql/lib/codeql/ruby/dataflow/internal/DataFlowDispatch.qll

@@ -191,13 +191,7 @@ private predicate moduleFlowsToMethodCallReceiver(RelevantCall call, Module m, s
   flowsToMethodCallReceiver(call, trackModuleAccess(m), method)
 }
 
-private Block yieldCall(RelevantCall call) {
-  call.getExpr() instanceof YieldCall and
-  exists(BlockParameterNode node |
-    node = trackBlock(result) and
-    node.getMethod() = call.getExpr().getEnclosingMethod()
-  )
-}
+private Block blockCall(RelevantCall call) { lambdaSourceCall(call, _, trackBlock(result)) }
 
 pragma[nomagic]
 private predicate superCall(RelevantCall call, Module cls, string method) {
@@ -297,7 +291,7 @@ predicate isUserDefinedNew(SingletonMethod new) {
 
 private Callable viableSourceCallableNonInit(RelevantCall call) {
   result = getTarget(call) and
-  not call.getExpr() instanceof YieldCall // handled by `lambdaCreation`/`lambdaCall`
+  not result = blockCall(call) // handled by `lambdaCreation`/`lambdaCall`
 }
 
 private Callable viableSourceCallableInit(RelevantCall call) { result = getInitializeTarget(call) }
@@ -394,7 +388,7 @@ private module Cached {
       result = lookupMethod(cls.getAnImmediateAncestor(), method)
     )
     or
-    result = yieldCall(call)
+    result = blockCall(call)
   }
 
   /** Gets a viable run-time target for the call `call`. */
@@ -700,13 +694,19 @@ private DataFlow::LocalSourceNode trackBlock(Block block, TypeTracker t) {
   t.start() and result.asExpr().getExpr() = block
   or
   exists(TypeTracker t2, StepSummary summary |
-    result = trackBlockRec(block, t2, summary) and t = t2.append(summary)
+    result = trackBlockRec(block, t2, summary) and
+    t = t2.append(summary)
   )
 }
 
+/**
+ * We exclude steps into `self` parameters, which may happen when the code
+ * base contains implementations of `call`.
+ */
 pragma[nomagic]
 private DataFlow::LocalSourceNode trackBlockRec(Block block, TypeTracker t, StepSummary summary) {
-  StepSummary::step(trackBlock(block, t), result, summary)
+  StepSummary::step(trackBlock(block, t), result, summary) and
+  not result instanceof SelfParameterNode
 }
 
 pragma[nomagic]

ruby/ql/lib/codeql/ruby/dataflow/internal/DataFlowPrivate.qll

@@ -1377,18 +1377,28 @@ predicate lambdaCreation(Node creation, LambdaCallKind kind, DataFlowCallable c)
   )
 }
 
-/** Holds if `call` is a lambda call of kind `kind` where `receiver` is the lambda expression. */
-predicate lambdaCall(DataFlowCall call, LambdaCallKind kind, Node receiver) {
+/**
+ * Holds if `call` is a from-source lambda call of kind `kind` where `receiver`
+ * is the lambda expression.
+ */
+predicate lambdaSourceCall(CfgNodes::ExprNodes::CallCfgNode call, LambdaCallKind kind, Node receiver) {
   kind = TYieldCallKind() and
-  receiver.(BlockParameterNode).getMethod() =
-    call.asCall().getExpr().(YieldCall).getEnclosingMethod()
+  receiver.(BlockParameterNode).getMethod() = call.getExpr().(YieldCall).getEnclosingMethod()
   or
   kind = TLambdaCallKind() and
-  call.asCall() =
+  call =
     any(CfgNodes::ExprNodes::MethodCallCfgNode mc |
       receiver.asExpr() = mc.getReceiver() and
       mc.getExpr().getMethodName() = "call"
     )
+}
+
+/**
+ * Holds if `call` is a (from-source or from-summary) lambda call of kind `kind`
+ * where `receiver` is the lambda expression.
+ */
+predicate lambdaCall(DataFlowCall call, LambdaCallKind kind, Node receiver) {
+  lambdaSourceCall(call.asCall(), kind, receiver)
   or
   receiver = call.(SummaryCall).getReceiver() and
   if receiver.(ParameterNodeImpl).isParameterOf(_, any(ParameterPosition pos | pos.isBlock()))