Data flow: Do not require stores to have matching reads in flow exploration

Author: hvitved

shared/dataflow/codeql/dataflow/internal/DataFlowImpl.qll

@@ -452,18 +452,22 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
     private predicate notExpectsContent(NodeEx n) { not expectsContentCached(n.asNode(), _) }
 
     pragma[nomagic]
-    private predicate hasReadStep(Content c) { read(_, c, _) }
-
-    pragma[nomagic]
-    private predicate storeEx(
+    private predicate storeExUnrestricted(
       NodeEx node1, Content c, NodeEx node2, DataFlowType contentType, DataFlowType containerType
     ) {
       store(pragma[only_bind_into](node1.asNode()), c, pragma[only_bind_into](node2.asNode()),
         contentType, containerType) and
-      hasReadStep(c) and
       stepFilter(node1, node2)
     }
 
+    pragma[nomagic]
+    private predicate storeEx(
+      NodeEx node1, Content c, NodeEx node2, DataFlowType contentType, DataFlowType containerType
+    ) {
+      storeExUnrestricted(node1, c, node2, contentType, containerType) and
+      read(_, c, _)
+    }
+
     pragma[nomagic]
     private predicate viableReturnPosOutEx(DataFlowCall call, ReturnPosition pos, NodeEx out) {
       viableReturnPosOut(call, pos, out.asNode())
@@ -5141,7 +5145,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
           midNode = mid.getNodeEx() and
           t1 = mid.getType() and
           ap1 = mid.getAp() and
-          storeEx(midNode, c, node, contentType, t2) and
+          storeExUnrestricted(midNode, c, node, contentType, t2) and
           ap2.getHead() = c and
           ap2.len() = unbindInt(ap1.len() + 1) and
           compatibleTypes(t1, contentType)
@@ -5318,7 +5322,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
           not outBarrier(node, state) and
           // if a node is not the target of a store, we can check `clearsContent` immediately
           (
-            storeEx(_, _, node, _, _)
+            storeExUnrestricted(_, _, node, _, _)
             or
             not clearsContentEx(node, ap.getHead())
           )
@@ -5459,7 +5463,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
         exists(NodeEx midNode |
           midNode = mid.getNodeEx() and
           ap = mid.getAp() and
-          storeEx(node, c, midNode, _, _) and
+          storeExUnrestricted(node, c, midNode, _, _) and
           ap.getHead() = c
         )
       }