Python: hotfix - disable instanceFieldStep to avoid type-tracker blowup

The `instanceFieldStep` disjunct of `TypeTrackingInput::levelStepCall`
that was added in 7.2.0 uses `classInstanceTracker(cls)` -- which is
itself a type-tracker -- inside `levelStepCall`. That creates a
structural mutual recursion between the main type-tracker fixpoint and
`classInstanceTracker`, causing the type-tracker delta to blow up to
~100M tuples per iteration on some OOP-heavy Python codebases.
Verified on the python/mypy database: SSRF query wall time goes from
~12s before the offending commit to >40 minutes after it.

This hotfix temporarily drops the `instanceFieldStep` disjunct and
keeps only `inheritedFieldStep`, which does not pull on the call
graph and is well-behaved (verified at ~12s on mypy). The
`instanceFieldStep` helper predicate itself is kept in place, and
the `levelStepCall` body has a commented-out call to it so the
change is trivial to re-enable once the recursion issue is properly
addressed.

Author: tausbn

python/ql/lib/change-notes/2026-06-30-disable-instance-field-step-hotfix.md

@@ -0,0 +1,5 @@
+---
+category: minorAnalysis
+---
+
+- Temporarily disabled the `instanceFieldStep` disjunct of the internal `TypeTrackingInput::levelStepCall` predicate, which was introduced in 7.2.0 and caused catastrophic query slowdowns on some OOP-heavy Python codebases (e.g. `mypy` and `dask`).

python/ql/lib/semmle/python/dataflow/new/internal/TypeTrackingImpl.qll

@@ -170,7 +170,13 @@ module TypeTrackingInput implements Shared::TypeTrackingInput<Location> {
 
   /** Holds if there is a level step from `nodeFrom` to `nodeTo`, which may depend on the call graph. */
   predicate levelStepCall(Node nodeFrom, LocalSourceNode nodeTo) {
-    instanceFieldStep(nodeFrom, nodeTo)
+    // HOTFIX: `instanceFieldStep` is temporarily disabled (via `and none()`).
+    // It uses `classInstanceTracker(cls)` -- itself a type-tracker run --
+    // from inside `levelStepCall`, creating a structural mutual recursion
+    // that causes catastrophic query slowdowns on some OOP-heavy Python
+    // codebases (e.g. mypy and dask). The `and none()` should be removed
+    // once that recursion is redesigned.
+    instanceFieldStep(nodeFrom, nodeTo) and none()
     or
     inheritedFieldStep(nodeFrom, nodeTo)
   }

python/ql/test/library-tests/dataflow/typetracking/attribute_tests.py

@@ -157,7 +157,7 @@ def possibly_uncalled_method(self): # $ MISSING: tracked=foo
         print(self.foo) # $ tracked MISSING: tracked=foo
 
 instance = MyClass2()
-print(instance.foo) # $ tracked MISSING: tracked=foo
+print(instance.foo) # $ MISSING: tracked=foo tracked
 instance.print_foo() # $ MISSING: tracked=foo
 
 
@@ -195,7 +195,7 @@ def read_foo(self): # $ MISSING: tracked=foo
 
 sub1 = Sub1()
 sub1.read_foo()
-print(sub1.foo) # $ tracked MISSING: tracked=foo
+print(sub1.foo) # $ MISSING: tracked=foo tracked
 
 
 # attribute written in a subclass method, read in an inherited base class method
@@ -210,7 +210,7 @@ def __init__(self): # $ tracked=bar
 
 sub2 = Sub2()
 sub2.read_bar()
-print(sub2.bar) # $ tracked MISSING: tracked=bar
+print(sub2.bar) # $ MISSING: tracked=bar tracked
 
 
 # attribute written in a base class method, read on an instance of the subclass
@@ -223,4 +223,4 @@ class Sub3(Base3):
     pass
 
 sub3 = Sub3()
-print(sub3.baz) # $ tracked MISSING: tracked=baz
+print(sub3.baz) # $ MISSING: tracked=baz tracked

python/ql/test/query-tests/Security/CWE-089-SqlInjection/SqlInjection.expected

@@ -1,7 +1,6 @@
 #select
 | app.py:23:20:23:24 | ControlFlowNode for query | app.py:20:18:20:21 | ControlFlowNode for name | app.py:23:20:23:24 | ControlFlowNode for query | This SQL query depends on a $@. | app.py:20:18:20:21 | ControlFlowNode for name | user-provided value |
 | app.py:30:20:30:24 | ControlFlowNode for query | app.py:27:19:27:22 | ControlFlowNode for name | app.py:30:20:30:24 | ControlFlowNode for query | This SQL query depends on a $@. | app.py:27:19:27:22 | ControlFlowNode for name | user-provided value |
-| app.py:37:20:37:24 | ControlFlowNode for query | app.py:34:19:34:22 | ControlFlowNode for name | app.py:37:20:37:24 | ControlFlowNode for query | This SQL query depends on a $@. | app.py:34:19:34:22 | ControlFlowNode for name | user-provided value |
 | app.py:44:20:44:24 | ControlFlowNode for query | app.py:41:19:41:22 | ControlFlowNode for name | app.py:44:20:44:24 | ControlFlowNode for query | This SQL query depends on a $@. | app.py:41:19:41:22 | ControlFlowNode for name | user-provided value |
 | app.py:51:20:51:24 | ControlFlowNode for query | app.py:48:19:48:22 | ControlFlowNode for name | app.py:51:20:51:24 | ControlFlowNode for query | This SQL query depends on a $@. | app.py:48:19:48:22 | ControlFlowNode for name | user-provided value |
 | sql_injection.py:21:24:21:77 | ControlFlowNode for BinaryExpr | sql_injection.py:14:15:14:22 | ControlFlowNode for username | sql_injection.py:21:24:21:77 | ControlFlowNode for BinaryExpr | This SQL query depends on a $@. | sql_injection.py:14:15:14:22 | ControlFlowNode for username | user-provided value |
@@ -25,8 +24,6 @@ edges
 | app.py:21:5:21:9 | ControlFlowNode for query | app.py:23:20:23:24 | ControlFlowNode for query | provenance |  |
 | app.py:27:19:27:22 | ControlFlowNode for name | app.py:28:5:28:9 | ControlFlowNode for query | provenance |  |
 | app.py:28:5:28:9 | ControlFlowNode for query | app.py:30:20:30:24 | ControlFlowNode for query | provenance |  |
-| app.py:34:19:34:22 | ControlFlowNode for name | app.py:35:5:35:9 | ControlFlowNode for query | provenance |  |
-| app.py:35:5:35:9 | ControlFlowNode for query | app.py:37:20:37:24 | ControlFlowNode for query | provenance |  |
 | app.py:41:19:41:22 | ControlFlowNode for name | app.py:42:5:42:9 | ControlFlowNode for query | provenance |  |
 | app.py:42:5:42:9 | ControlFlowNode for query | app.py:44:20:44:24 | ControlFlowNode for query | provenance |  |
 | app.py:48:19:48:22 | ControlFlowNode for name | app.py:49:5:49:9 | ControlFlowNode for query | provenance |  |
@@ -54,9 +51,6 @@ nodes
 | app.py:27:19:27:22 | ControlFlowNode for name | semmle.label | ControlFlowNode for name |
 | app.py:28:5:28:9 | ControlFlowNode for query | semmle.label | ControlFlowNode for query |
 | app.py:30:20:30:24 | ControlFlowNode for query | semmle.label | ControlFlowNode for query |
-| app.py:34:19:34:22 | ControlFlowNode for name | semmle.label | ControlFlowNode for name |
-| app.py:35:5:35:9 | ControlFlowNode for query | semmle.label | ControlFlowNode for query |
-| app.py:37:20:37:24 | ControlFlowNode for query | semmle.label | ControlFlowNode for query |
 | app.py:41:19:41:22 | ControlFlowNode for name | semmle.label | ControlFlowNode for name |
 | app.py:42:5:42:9 | ControlFlowNode for query | semmle.label | ControlFlowNode for query |
 | app.py:44:20:44:24 | ControlFlowNode for query | semmle.label | ControlFlowNode for query |

python/ql/test/query-tests/Security/CWE-089-SqlInjection/app.py

@@ -31,10 +31,10 @@ async def unsafe2(name: str): # $ Source
     cursor.close()
 
 @app.get("/unsafe3/")
-async def unsafe3(name: str): # $ Source
+async def unsafe3(name: str): # $ MISSING: Source
     query = "select * from users where name=" + name
     cursor = hdb_con3.cursor()
-    cursor.execute(query) # $ Alert
+    cursor.execute(query) # $ MISSING: Alert
     cursor.close()
 
 @app.get("/unsafe4/")