fix(internal): closure bytecode wrapping for Python 3.11 [backport #7044 to 1.20] (#7065)

Backport of #7044 to 1.20

We fix the bytecode wrapping for closures to ensure that the frame
objects don't end up referencing missing data, ultimately resulting in a
segmentation fault in profiling tools.

Fixes #6701.

## Checklist

- [x] Change(s) are motivated and described in the PR description.
- [x] Testing strategy is described if automated tests are not included
in the PR.
- [x] Risk is outlined (performance impact, potential for breakage,
maintainability, etc).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] [Library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
are followed. If no release note is required, add label
`changelog/no-changelog`.
- [x] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/)).
- [x] Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist

- [x] Title is accurate.
- [x] No unnecessary changes are introduced.
- [x] Description motivates each change.
- [x] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes unless absolutely necessary.
- [x] Testing strategy adequately addresses listed risk(s).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] Release note makes sense to a user of the library.
- [x] Reviewer has explicitly acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment.
- [x] Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)
- [x] If this PR touches code that signs or publishes builds or
packages, or handles credentials of any kind, I've requested a review
from `@DataDog/security-design-and-guidance`.
- [x] This PR doesn't touch any of that.

Co-authored-by: Emmett Butler <[email protected]>

Author: P403n1x87

ddtrace/internal/wrapping/__init__.py

@@ -115,15 +115,30 @@ def wrap_bytecode(wrapper, wrapped):
         Instr("LOAD_CONST", wrapped, lineno=lineno),
     ]
     if PY >= (3, 11):
-        # THis is required to start a new frame
+        # From insert_prefix_instructions
         instrs[0:0] = [
             Instr("RESUME", 0, lineno=lineno - 1),
             Instr("PUSH_NULL", lineno=lineno),
         ]
 
+        if code.co_cellvars:
+            from bytecode import CellVar
+
+            instrs[0:0] = [Instr("MAKE_CELL", CellVar(_), lineno=lineno) for _ in code.co_cellvars]
+
+        if code.co_freevars:
+            instrs.insert(0, Instr("COPY_FREE_VARS", len(code.co_freevars), lineno=lineno))
+
     # Build the tuple of all the positional arguments
     if nargs:
-        instrs.extend([Instr("LOAD_FAST", argname, lineno=lineno) for argname in argnames])
+        instrs.extend(
+            [
+                Instr("LOAD_DEREF", CellVar(argname), lineno=lineno)
+                if PY >= (3, 11) and argname in code.co_cellvars
+                else Instr("LOAD_FAST", argname, lineno=lineno)
+                for argname in argnames
+            ]
+        )
         instrs.append(Instr("BUILD_TUPLE", nargs, lineno=lineno))
         if varargs:
             instrs.extend(
@@ -198,6 +213,8 @@ def wrap(f, wrapper):
 
     code = wrap_bytecode(wrapper, wrapped)
     code.freevars = f.__code__.co_freevars
+    if PY >= (3, 11):
+        code.cellvars = f.__code__.co_cellvars
     code.name = f.__code__.co_name
     code.filename = f.__code__.co_filename
     code.flags = f.__code__.co_flags

releasenotes/notes/fix-py311-closure-wrapping-fed33b584d65a844.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fix an issue that could have caused some tracing integrations to create
+    invalid references to objects in Python frames, ultimately causing profiling
+    tools to potentially induce a segmentation fault.

tests/internal/test_wrapping.py

@@ -202,3 +202,27 @@ def f():
     wrap(f, wrapper)
 
     assert [frame.f_code.co_name for frame in f()[:4]] == ["f", "wrapper", "f", "test_wrap_stack"]
+
+
+def test_wrap_closure():
+    channel = []
+
+    def wrapper(f, args, kwargs):
+        channel.append((args, kwargs))
+        retval = f(*args, **kwargs)
+        channel.append(retval)
+        return retval
+
+    def outer(answer=42):
+        def f(a, b, c=None):
+            return (a, b, c, answer)
+
+        return f
+
+    wrap(outer, wrapper)
+
+    closure = outer()
+    wrap(closure, wrapper)
+
+    assert closure(1, 2, 3) == (1, 2, 3, 42)
+    assert channel == [((42,), {}), closure, ((1, 2, 3), {}), (1, 2, 3, 42)]