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Check the GIL in PyObject_Malloc() 

Issue #26558: The debug hook of PyObject_Malloc() now checks that the GIL is
held when the function is called.
This commit is contained in:
Victor Stinner 2016-03-14 22:26:53 +01:00
parent 8a1be61849
commit c4aec3628b
6 changed files with 119 additions and 34 deletions
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9
Doc/c-api/memory.rst
View File

@ -341,10 +341,13 @@ Customize Memory Allocators
Newly allocated memory is filled with the byte ``0xCB``, freed memory is
filled with the byte ``0xDB``. Additional checks:
- detect API violations, ex: :c:func:`PyObject_Free` called on a buffer
- Detect API violations, ex: :c:func:`PyObject_Free` called on a buffer
allocated by :c:func:`PyMem_Malloc`
- detect write before the start of the buffer (buffer underflow)
- detect write after the end of the buffer (buffer overflow)
- Detect write before the start of the buffer (buffer underflow)
- Detect write after the end of the buffer (buffer overflow)
- Check that the :term:`GIL <global interpreter lock>` is held when
allocator functions of the :c:data:`PYMEM_DOMAIN_OBJ` domain (ex:
:c:func:`PyObject_Malloc`) are called
These hooks are installed by default if Python is compiled in debug
mode. The :envvar:`PYTHONMALLOC` environment variable can be used to install

3
Doc/whatsnew/3.6.rst
View File

@ -117,6 +117,9 @@ compiled in release mode using ``PYTHONMALLOC=debug``. Effects of debug hooks:
:c:func:`PyMem_Malloc`.
* Detect write before the start of the buffer (buffer underflow)
* Detect write after the end of the buffer (buffer overflow)
* Check that the :term:`GIL <global interpreter lock>` is held when allocator
functions of the :c:data:`PYMEM_DOMAIN_OBJ` domain (ex:
:c:func:`PyObject_Malloc`) are called
See the :c:func:`PyMem_SetupDebugHooks` function for debug hooks on Python
memory allocators.

30
Lib/test/test_capi.py
View File

@ -441,6 +441,7 @@ class EmbeddingTests(unittest.TestCase):
self.maxDiff = None
self.assertEqual(out.strip(), expected_output)
class SkipitemTest(unittest.TestCase):
def test_skipitem(self):
@ -558,14 +559,15 @@ class Test_testcapi(unittest.TestCase):
test()
class MallocTests(unittest.TestCase):
ENV = 'debug'
class PyMemDebugTests(unittest.TestCase):
PYTHONMALLOC = 'debug'
# '0x04c06e0' or '04C06E0'
PTR_REGEX = r'(?:0x)?[0-9a-fA-F]+'
def check(self, code):
with support.SuppressCrashReport():
out = assert_python_failure('-c', code, PYTHONMALLOC=self.ENV)
out = assert_python_failure('-c', code,
PYTHONMALLOC=self.PYTHONMALLOC)
stderr = out.err
return stderr.decode('ascii', 'replace')
@ -598,20 +600,30 @@ class MallocTests(unittest.TestCase):
regex = regex.format(ptr=self.PTR_REGEX)
self.assertRegex(out, regex)
def test_pyobject_malloc_without_gil(self):
# Calling PyObject_Malloc() without holding the GIL must raise an
# error in debug mode.
code = 'import _testcapi; _testcapi.pyobject_malloc_without_gil()'
out = self.check(code)
expected = ('Fatal Python error: Python memory allocator called '
'without holding the GIL')
self.assertIn(expected, out)
class MallocDebugTests(MallocTests):
ENV = 'malloc_debug'
class PyMemMallocDebugTests(PyMemDebugTests):
PYTHONMALLOC = 'malloc_debug'
@unittest.skipUnless(sysconfig.get_config_var('WITH_PYMALLOC') == 1,
'need pymalloc')
class PymallocDebugTests(MallocTests):
ENV = 'pymalloc_debug'
class PyMemPymallocDebugTests(PyMemDebugTests):
PYTHONMALLOC = 'pymalloc_debug'
@unittest.skipUnless(Py_DEBUG, 'need Py_DEBUG')
class DefaultMallocDebugTests(MallocTests):
ENV = ''
class PyMemDefaultTests(PyMemDebugTests):
# test default allocator of Python compiled in debug mode
PYTHONMALLOC = ''
if __name__ == "__main__":

4
Misc/NEWS
View File

@ -10,6 +10,10 @@ Release date: tba
Core and Builtins
-----------------
- Issue #26558: The debug hooks on Python memory allocator
:c:func:`PyObject_Malloc` now detect when functions are called without
holding the GIL.
- Issue #26516: Add :envvar`PYTHONMALLOC` environment variable to set the
Python memory allocators and/or install debug hooks.

15
Modules/_testcapimodule.c
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@ -3643,6 +3643,20 @@ pymem_api_misuse(PyObject *self, PyObject *args)
Py_RETURN_NONE;
}
static PyObject*
pyobject_malloc_without_gil(PyObject *self, PyObject *args)
{
char *buffer;
Py_BEGIN_ALLOW_THREADS
buffer = PyObject_Malloc(10);
Py_END_ALLOW_THREADS
PyObject_Free(buffer);
Py_RETURN_NONE;
}
static PyMethodDef TestMethods[] = {
{"raise_exception", raise_exception, METH_VARARGS},
@ -3827,6 +3841,7 @@ static PyMethodDef TestMethods[] = {
{"get_recursion_depth", get_recursion_depth, METH_NOARGS},
{"pymem_buffer_overflow", pymem_buffer_overflow, METH_NOARGS},
{"pymem_api_misuse", pymem_api_misuse, METH_NOARGS},
{"pyobject_malloc_without_gil", pyobject_malloc_without_gil, METH_NOARGS},
{NULL, NULL} /* sentinel */
};

92
Objects/obmalloc.c
View File

@ -16,10 +16,15 @@
#define uptr Py_uintptr_t
/* Forward declaration */
static void* _PyMem_DebugRawMalloc(void *ctx, size_t size);
static void* _PyMem_DebugRawCalloc(void *ctx, size_t nelem, size_t elsize);
static void* _PyMem_DebugRawRealloc(void *ctx, void *ptr, size_t size);
static void _PyMem_DebugRawFree(void *ctx, void *p);
static void* _PyMem_DebugMalloc(void *ctx, size_t size);
static void* _PyMem_DebugCalloc(void *ctx, size_t nelem, size_t elsize);
static void _PyMem_DebugFree(void *ctx, void *p);
static void* _PyMem_DebugRealloc(void *ctx, void *ptr, size_t size);
static void _PyMem_DebugFree(void *ctx, void *p);
static void _PyObject_DebugDumpAddress(const void *p);
static void _PyMem_DebugCheckAddress(char api_id, const void *p);
@ -173,11 +178,14 @@ static struct {
{'o', {NULL, PYOBJ_FUNCS}}
};
#define PYDBG_FUNCS _PyMem_DebugMalloc, _PyMem_DebugCalloc, _PyMem_DebugRealloc, _PyMem_DebugFree
#define PYRAWDBG_FUNCS \
_PyMem_DebugRawMalloc, _PyMem_DebugRawCalloc, _PyMem_DebugRawRealloc, _PyMem_DebugRawFree
#define PYDBG_FUNCS \
_PyMem_DebugMalloc, _PyMem_DebugCalloc, _PyMem_DebugRealloc, _PyMem_DebugFree
static PyMemAllocatorEx _PyMem_Raw = {
#ifdef Py_DEBUG
&_PyMem_Debug.raw, PYDBG_FUNCS
&_PyMem_Debug.raw, PYRAWDBG_FUNCS
#else
NULL, PYRAW_FUNCS
#endif
@ -185,7 +193,7 @@ static PyMemAllocatorEx _PyMem_Raw = {
static PyMemAllocatorEx _PyMem = {
#ifdef Py_DEBUG
&_PyMem_Debug.mem, PYDBG_FUNCS
&_PyMem_Debug.mem, PYRAWDBG_FUNCS
#else
NULL, PYMEM_FUNCS
#endif
@ -260,6 +268,7 @@ _PyMem_SetupAllocators(const char *opt)
#undef PYRAW_FUNCS
#undef PYMEM_FUNCS
#undef PYOBJ_FUNCS
#undef PYRAWDBG_FUNCS
#undef PYDBG_FUNCS
static PyObjectArenaAllocator _PyObject_Arena = {NULL,
@ -296,27 +305,28 @@ PyMem_SetupDebugHooks(void)
{
PyMemAllocatorEx alloc;
/* hooks already installed */
if (_PyMem_DebugEnabled())
return;
alloc.malloc = _PyMem_DebugRawMalloc;
alloc.calloc = _PyMem_DebugRawCalloc;
alloc.realloc = _PyMem_DebugRawRealloc;
alloc.free = _PyMem_DebugRawFree;
alloc.malloc = _PyMem_DebugMalloc;
alloc.calloc = _PyMem_DebugCalloc;
alloc.realloc = _PyMem_DebugRealloc;
alloc.free = _PyMem_DebugFree;
if (_PyMem_Raw.malloc != _PyMem_DebugMalloc) {
if (_PyMem_Raw.malloc != _PyMem_DebugRawMalloc) {
alloc.ctx = &_PyMem_Debug.raw;
PyMem_GetAllocator(PYMEM_DOMAIN_RAW, &_PyMem_Debug.raw.alloc);
PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &alloc);
}
if (_PyMem.malloc != _PyMem_DebugMalloc) {
if (_PyMem.malloc != _PyMem_DebugRawMalloc) {
alloc.ctx = &_PyMem_Debug.mem;
PyMem_GetAllocator(PYMEM_DOMAIN_MEM, &_PyMem_Debug.mem.alloc);
PyMem_SetAllocator(PYMEM_DOMAIN_MEM, &alloc);
}
alloc.malloc = _PyMem_DebugMalloc;
alloc.calloc = _PyMem_DebugCalloc;
alloc.realloc = _PyMem_DebugRealloc;
alloc.free = _PyMem_DebugFree;
if (_PyObject.malloc != _PyMem_DebugMalloc) {
alloc.ctx = &_PyMem_Debug.obj;
PyMem_GetAllocator(PYMEM_DOMAIN_OBJ, &_PyMem_Debug.obj.alloc);
@ -1869,7 +1879,7 @@ p[2*S+n+S: 2*S+n+2*S]
*/
static void *
_PyMem_DebugAlloc(int use_calloc, void *ctx, size_t nbytes)
_PyMem_DebugRawAlloc(int use_calloc, void *ctx, size_t nbytes)
{
debug_alloc_api_t *api = (debug_alloc_api_t *)ctx;
uchar *p; /* base address of malloc'ed block */
@ -1906,18 +1916,18 @@ _PyMem_DebugAlloc(int use_calloc, void *ctx, size_t nbytes)
}
static void *
_PyMem_DebugMalloc(void *ctx, size_t nbytes)
_PyMem_DebugRawMalloc(void *ctx, size_t nbytes)
{
return _PyMem_DebugAlloc(0, ctx, nbytes);
return _PyMem_DebugRawAlloc(0, ctx, nbytes);
}
static void *
_PyMem_DebugCalloc(void *ctx, size_t nelem, size_t elsize)
_PyMem_DebugRawCalloc(void *ctx, size_t nelem, size_t elsize)
{
size_t nbytes;
assert(elsize == 0 || nelem <= PY_SSIZE_T_MAX / elsize);
nbytes = nelem * elsize;
return _PyMem_DebugAlloc(1, ctx, nbytes);
return _PyMem_DebugRawAlloc(1, ctx, nbytes);
}
/* The debug free first checks the 2*SST bytes on each end for sanity (in
@ -1926,7 +1936,7 @@ _PyMem_DebugCalloc(void *ctx, size_t nelem, size_t elsize)
Then calls the underlying free.
*/
static void
_PyMem_DebugFree(void *ctx, void *p)
_PyMem_DebugRawFree(void *ctx, void *p)
{
debug_alloc_api_t *api = (debug_alloc_api_t *)ctx;
uchar *q = (uchar *)p - 2*SST; /* address returned from malloc */
@ -1943,7 +1953,7 @@ _PyMem_DebugFree(void *ctx, void *p)
}
static void *
_PyMem_DebugRealloc(void *ctx, void *p, size_t nbytes)
_PyMem_DebugRawRealloc(void *ctx, void *p, size_t nbytes)
{
debug_alloc_api_t *api = (debug_alloc_api_t *)ctx;
uchar *q = (uchar *)p, *oldq;
@ -1953,7 +1963,7 @@ _PyMem_DebugRealloc(void *ctx, void *p, size_t nbytes)
int i;
if (p == NULL)
return _PyMem_DebugAlloc(0, ctx, nbytes);
return _PyMem_DebugRawAlloc(0, ctx, nbytes);
_PyMem_DebugCheckAddress(api->api_id, p);
bumpserialno();
@ -1996,6 +2006,44 @@ _PyMem_DebugRealloc(void *ctx, void *p, size_t nbytes)
return q;
}
static void
_PyMem_DebugCheckGIL(void)
{
#ifdef WITH_THREAD
if (!PyGILState_Check())
Py_FatalError("Python memory allocator called "
"without holding the GIL");
#endif
}
static void *
_PyMem_DebugMalloc(void *ctx, size_t nbytes)
{
_PyMem_DebugCheckGIL();
return _PyMem_DebugRawMalloc(ctx, nbytes);
}
static void *
_PyMem_DebugCalloc(void *ctx, size_t nelem, size_t elsize)
{
_PyMem_DebugCheckGIL();
return _PyMem_DebugRawCalloc(ctx, nelem, elsize);
}
static void
_PyMem_DebugFree(void *ctx, void *ptr)
{
_PyMem_DebugCheckGIL();
return _PyMem_DebugRawFree(ctx, ptr);
}
static void *
_PyMem_DebugRealloc(void *ctx, void *ptr, size_t nbytes)
{
_PyMem_DebugCheckGIL();
return _PyMem_DebugRawRealloc(ctx, ptr, nbytes);
}
/* Check the forbidden bytes on both ends of the memory allocated for p.
* If anything is wrong, print info to stderr via _PyObject_DebugDumpAddress,
* and call Py_FatalError to kill the program.