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gh-140815: Fix faulthandler for invalid/freed frame (#140921)

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faulthandler now detects if a frame or a code object is invalid or
freed.

Add helper functions:

* _PyCode_SafeAddr2Line()
* _PyFrame_SafeGetCode()
* _PyFrame_SafeGetLasti()

_PyMem_IsPtrFreed() now detects pointers in [-0xff, 0xff] range
as freed.
This commit is contained in:
Victor Stinner 2025-11-04 11:48:28 +01:00 • committed by GitHub
parent 08115d241a
commit a84181c31b
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GPG key ID: B5690EEEBB952194
6 changed files with 128 additions and 33 deletions
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55
Include/internal/pycore_interpframe.h
View file

@ -24,6 +24,36 @@ static inline PyCodeObject *_PyFrame_GetCode(_PyInterpreterFrame *f) {
return (PyCodeObject *)executable;
}
// Similar to _PyFrame_GetCode(), but return NULL if the frame is invalid or
// freed. Used by dump_frame() in Python/traceback.c. The function uses
// heuristics to detect freed memory, it's not 100% reliable.
static inline PyCodeObject*
_PyFrame_SafeGetCode(_PyInterpreterFrame *f)
{
// globals and builtins may be NULL on a legit frame, but it's unlikely.
// It's more likely that it's a sign of an invalid frame.
if (f->f_globals == NULL || f->f_builtins == NULL) {
return NULL;
}
if (PyStackRef_IsNull(f->f_executable)) {
return NULL;
}
void *ptr;
memcpy(&ptr, &f->f_executable, sizeof(f->f_executable));
if (_PyMem_IsPtrFreed(ptr)) {
return NULL;
}
PyObject *executable = PyStackRef_AsPyObjectBorrow(f->f_executable);
if (_PyObject_IsFreed(executable)) {
return NULL;
}
if (!PyCode_Check(executable)) {
return NULL;
}
return (PyCodeObject *)executable;
}
static inline _Py_CODEUNIT *
_PyFrame_GetBytecode(_PyInterpreterFrame *f)
{
@ -37,6 +67,31 @@ _PyFrame_GetBytecode(_PyInterpreterFrame *f)
#endif
}
// Similar to PyUnstable_InterpreterFrame_GetLasti(), but return NULL if the
// frame is invalid or freed. Used by dump_frame() in Python/traceback.c. The
// function uses heuristics to detect freed memory, it's not 100% reliable.
static inline int
_PyFrame_SafeGetLasti(struct _PyInterpreterFrame *f)
{
// Code based on _PyFrame_GetBytecode() but replace _PyFrame_GetCode()
// with _PyFrame_SafeGetCode().
PyCodeObject *co = _PyFrame_SafeGetCode(f);
if (co == NULL) {
return -1;
}
_Py_CODEUNIT *bytecode;
#ifdef Py_GIL_DISABLED
_PyCodeArray *tlbc = _PyCode_GetTLBCArray(co);
assert(f->tlbc_index >= 0 && f->tlbc_index < tlbc->size);
bytecode = (_Py_CODEUNIT *)tlbc->entries[f->tlbc_index];
#else
bytecode = _PyCode_CODE(co);
#endif
return (int)(f->instr_ptr - bytecode) * sizeof(_Py_CODEUNIT);
}
static inline PyFunctionObject *_PyFrame_GetFunction(_PyInterpreterFrame *f) {
PyObject *func = PyStackRef_AsPyObjectBorrow(f->f_funcobj);
assert(PyFunction_Check(func));