contrib/fuzz/pyutil.cc

dirstate-v2: add check of parent/child nodes being related when writing

This stems from a corruption seen in a private repository. We're not sure
of the source of the corruption, and it's very possible that we're seeing
compounded effects of multiple writes on a corrupted dirstate.

Adding this check is not expensive in itself and large writes of the dirstate
are not common.

This change does not catch this problem at the root node, the next one will.

#include "pyutil.h"

#include <iostream>
#include <string>

namespace contrib
{

#if PY_MAJOR_VERSION >= 3
#define HG_FUZZER_PY3 1
PyMODINIT_FUNC PyInit_parsers(void);
#else
PyMODINIT_FUNC initparsers(void);
#endif

static char cpypath[8192] = "\0";

static PyObject *mainmod;
static PyObject *globals;

void initpy(const char *cselfpath)
{
#ifdef HG_FUZZER_PY3
	const std::string subdir = "/sanpy/lib/python3.8";
#else
	const std::string subdir = "/sanpy/lib/python2.7";
#endif

	/* HACK ALERT: we need a full Python installation built without
	   pymalloc and with ASAN, so we dump one in
	   $OUT/sanpy/lib/python2.7. This helps us wire that up. */
	std::string selfpath(cselfpath);
	std::string pypath;
	auto pos = selfpath.rfind("/");
	if (pos == std::string::npos) {
		char wd[8192];
		if (!getcwd(wd, 8192)) {
			std::cerr << "Failed to call getcwd: errno " << errno
			          << std::endl;
			exit(1);
		}
		pypath = std::string(wd) + subdir;
	} else {
		pypath = selfpath.substr(0, pos) + subdir;
	}
	strncpy(cpypath, pypath.c_str(), pypath.size());
	setenv("PYTHONPATH", cpypath, 1);
	setenv("PYTHONNOUSERSITE", "1", 1);
	/* prevent Python from looking up users in the fuzz environment */
	setenv("PYTHONUSERBASE", cpypath, 1);
#ifdef HG_FUZZER_PY3
	std::wstring wcpypath(pypath.begin(), pypath.end());
	Py_SetPythonHome(wcpypath.c_str());
#else
	Py_SetPythonHome(cpypath);
#endif
	Py_InitializeEx(0);
	mainmod = PyImport_AddModule("__main__");
	globals = PyModule_GetDict(mainmod);

#ifdef HG_FUZZER_PY3
	PyObject *mod = PyInit_parsers();
#else
	initparsers();
	PyObject *mod = PyImport_ImportModule("parsers");
#endif

	PyDict_SetItemString(globals, "parsers", mod);
}

PyObject *pyglobals()
{
	return globals;
}

} // namespace contrib