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Merged
merged 3 commits into from
May 14, 2025
Merged

gh-127081: add critical sections to dbm objects #132749

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83a05d5
gh-127081: add critical sections to dbm objects
duaneg Apr 17, 2025
0774870
Switch to calling a *_lock_held variant while holding the critical se…
duaneg Apr 20, 2025
a1d76d6
Merge branch 'main' into gh-127081-dbm
kumaraditya303 May 8, 2025
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2025-04-21-01-05-14.gh-issue-127081.Egrpq7.rst
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fix libc thread safety issues with :mod:`dbm` by performing stateful
operations in critical sections.
102 changes: 73 additions & 29 deletions Modules/_dbmmodule.c
View file
Original file line number Diff line number Diff line change
@@ -68,6 +68,7 @@ typedef struct {

#include "clinic/_dbmmodule.c.h"

/* NOTE: Must be used within a critical section! */
#define check_dbmobject_open(v, err) \
if ((v)->di_dbm == NULL) { \
PyErr_SetString(err, "DBM object has already been closed"); \
@@ -118,12 +119,15 @@ dbm_dealloc(PyObject *self)
static Py_ssize_t
dbm_length(PyObject *self)
{
Py_ssize_t result = -1;
dbmobject *dp = dbmobject_CAST(self);
_dbm_state *state = PyType_GetModuleState(Py_TYPE(dp));
assert(state != NULL);

Py_BEGIN_CRITICAL_SECTION(self);
if (dp->di_dbm == NULL) {
PyErr_SetString(state->dbm_error, "DBM object has already been closed");
return -1;
goto done;
}
if ( dp->di_size < 0 ) {
datum key;
@@ -135,73 +139,95 @@ dbm_length(PyObject *self)
size++;
dp->di_size = size;
}
return dp->di_size;
result = dp->di_size;
done:;
Py_END_CRITICAL_SECTION();
return result;
}

static int
dbm_bool(PyObject *self)
{
int result;
dbmobject *dp = dbmobject_CAST(self);
_dbm_state *state = PyType_GetModuleState(Py_TYPE(dp));
assert(state != NULL);

Py_BEGIN_CRITICAL_SECTION(self);
if (dp->di_dbm == NULL) {
PyErr_SetString(state->dbm_error, "DBM object has already been closed");
return -1;
result = -1;
goto done;
}

if (dp->di_size > 0) {
/* Known non-zero size. */
return 1;
result = 1;
goto done;
}
if (dp->di_size == 0) {
/* Known zero size. */
return 0;
result = 0;
goto done;
}

/* Unknown size. Ensure DBM object has an entry. */
datum key = dbm_firstkey(dp->di_dbm);
if (key.dptr == NULL) {
/* Empty. Cache this fact. */
dp->di_size = 0;
return 0;
result = dp->di_size = 0;
goto done;
}

/* Non-empty. Don't cache the length since we don't know. */
return 1;
result = 1;
done:;
Py_END_CRITICAL_SECTION();
return result;
}

static PyObject *
dbm_subscript(PyObject *self, PyObject *key)
{
datum drec, krec;
Py_ssize_t tmp_size;
PyObject *result = NULL;
dbmobject *dp = dbmobject_CAST(self);
_dbm_state *state = PyType_GetModuleState(Py_TYPE(dp));
assert(state != NULL);
if (!PyArg_Parse(key, "s#", &krec.dptr, &tmp_size)) {
return NULL;
}

krec.dsize = tmp_size;
check_dbmobject_open(dp, state->dbm_error);

Py_BEGIN_CRITICAL_SECTION(self);
/* Can't use the macro here as it returns. */
if (dp->di_dbm == NULL) {
PyErr_SetString(state->dbm_error, "DBM object has already been closed");
goto done;
}
drec = dbm_fetch(dp->di_dbm, krec);
if ( drec.dptr == 0 ) {
PyErr_SetObject(PyExc_KeyError, key);
return NULL;
goto done;
}
if ( dbm_error(dp->di_dbm) ) {
dbm_clearerr(dp->di_dbm);
PyErr_SetString(state->dbm_error, "");
return NULL;
goto done;
}
return PyBytes_FromStringAndSize(drec.dptr, drec.dsize);
result = PyBytes_FromStringAndSize(drec.dptr, drec.dsize);
done:;
Py_END_CRITICAL_SECTION();
return result;
}

static int
dbm_ass_sub(PyObject *self, PyObject *v, PyObject *w)
{
datum krec, drec;
Py_ssize_t tmp_size;
int result = -1;
dbmobject *dp = dbmobject_CAST(self);

if ( !PyArg_Parse(v, "s#", &krec.dptr, &tmp_size) ) {
@@ -212,10 +238,13 @@ dbm_ass_sub(PyObject *self, PyObject *v, PyObject *w)
_dbm_state *state = PyType_GetModuleState(Py_TYPE(dp));
assert(state != NULL);
krec.dsize = tmp_size;

Py_BEGIN_CRITICAL_SECTION(self);
if (dp->di_dbm == NULL) {
PyErr_SetString(state->dbm_error, "DBM object has already been closed");
return -1;
PyErr_SetString(state->dbm_error, "DBM object has already been closed");
goto done;
}

dp->di_size = -1;
if (w == NULL) {
if ( dbm_delete(dp->di_dbm, krec) < 0 ) {
@@ -228,39 +257,44 @@ dbm_ass_sub(PyObject *self, PyObject *v, PyObject *w)
else {
PyErr_SetString(state->dbm_error, "cannot delete item from database");
}
return -1;
goto done;
}
} else {
if ( !PyArg_Parse(w, "s#", &drec.dptr, &tmp_size) ) {
PyErr_SetString(PyExc_TypeError,
"dbm mappings have bytes or string elements only");
return -1;
goto done;
}
drec.dsize = tmp_size;
if ( dbm_store(dp->di_dbm, krec, drec, DBM_REPLACE) < 0 ) {
dbm_clearerr(dp->di_dbm);
PyErr_SetString(state->dbm_error,
"cannot add item to database");
return -1;
goto done;
}
}
if ( dbm_error(dp->di_dbm) ) {
dbm_clearerr(dp->di_dbm);
PyErr_SetString(state->dbm_error, "");
return -1;
goto done;
}
return 0;

result = 0;
done:;
Py_END_CRITICAL_SECTION();
return result;
}

/*[clinic input]
@critical_section
_dbm.dbm.close

Close the database.
[clinic start generated code]*/

static PyObject *
_dbm_dbm_close_impl(dbmobject *self)
/*[clinic end generated code: output=c8dc5b6709600b86 input=046db72377d51be8]*/
/*[clinic end generated code: output=c8dc5b6709600b86 input=4a94f79facbc28ca]*/
{
if (self->di_dbm) {
dbm_close(self->di_dbm);
@@ -270,6 +304,7 @@ _dbm_dbm_close_impl(dbmobject *self)
}

/*[clinic input]
@critical_section
_dbm.dbm.keys

cls: defining_class
@@ -279,7 +314,7 @@ Return a list of all keys in the database.

static PyObject *
_dbm_dbm_keys_impl(dbmobject *self, PyTypeObject *cls)
/*[clinic end generated code: output=f2a593b3038e5996 input=d3706a28fc051097]*/
/*[clinic end generated code: output=f2a593b3038e5996 input=6ddefeadf2a80156]*/
{
PyObject *v, *item;
datum key;
@@ -315,35 +350,42 @@ dbm_contains(PyObject *self, PyObject *arg)
dbmobject *dp = dbmobject_CAST(self);
datum key, val;
Py_ssize_t size;
int result = -1;

_dbm_state *state = PyType_GetModuleState(Py_TYPE(dp));
assert(state != NULL);

Py_BEGIN_CRITICAL_SECTION(self);
if ((dp)->di_dbm == NULL) {
PyErr_SetString(state->dbm_error,
"DBM object has already been closed");
return -1;
goto done;
}
if (PyUnicode_Check(arg)) {
key.dptr = (char *)PyUnicode_AsUTF8AndSize(arg, &size);
key.dsize = size;
if (key.dptr == NULL)
return -1;
goto done;
}
else if (!PyBytes_Check(arg)) {
PyErr_Format(PyExc_TypeError,
"dbm key must be bytes or string, not %.100s",
Py_TYPE(arg)->tp_name);
return -1;
goto done;
}
else {
key.dptr = PyBytes_AS_STRING(arg);
key.dsize = PyBytes_GET_SIZE(arg);
}
val = dbm_fetch(dp->di_dbm, key);
return val.dptr != NULL;
result = val.dptr != NULL;
done:;
Py_END_CRITICAL_SECTION();
return result;
}

/*[clinic input]
@critical_section
_dbm.dbm.get
cls: defining_class
key: str(accept={str, robuffer}, zeroes=True)
@@ -356,7 +398,7 @@ Return the value for key if present, otherwise default.
static PyObject *
_dbm_dbm_get_impl(dbmobject *self, PyTypeObject *cls, const char *key,
Py_ssize_t key_length, PyObject *default_value)
/*[clinic end generated code: output=b4e55f8b6d482bc4 input=66b993b8349fa8c1]*/
/*[clinic end generated code: output=b4e55f8b6d482bc4 input=1d88a22bb5e55202]*/
{
datum dbm_key, val;
_dbm_state *state = PyType_GetModuleState(cls);
@@ -373,6 +415,7 @@ _dbm_dbm_get_impl(dbmobject *self, PyTypeObject *cls, const char *key,
}

/*[clinic input]
@critical_section
_dbm.dbm.setdefault
cls: defining_class
key: str(accept={str, robuffer}, zeroes=True)
@@ -387,7 +430,7 @@ If key is not in the database, it is inserted with default as the value.
static PyObject *
_dbm_dbm_setdefault_impl(dbmobject *self, PyTypeObject *cls, const char *key,
Py_ssize_t key_length, PyObject *default_value)
/*[clinic end generated code: output=9c2f6ea6d0fb576c input=126a3ff15c5f8232]*/
/*[clinic end generated code: output=9c2f6ea6d0fb576c input=c01510ef7571e13b]*/
{
datum dbm_key, val;
Py_ssize_t tmp_size;
@@ -427,6 +470,7 @@ _dbm_dbm_setdefault_impl(dbmobject *self, PyTypeObject *cls, const char *key,
}

/*[clinic input]
@critical_section
_dbm.dbm.clear
cls: defining_class
/
@@ -436,7 +480,7 @@ Remove all items from the database.

static PyObject *
_dbm_dbm_clear_impl(dbmobject *self, PyTypeObject *cls)
/*[clinic end generated code: output=8d126b9e1d01a434 input=43aa6ca1acb7f5f5]*/
/*[clinic end generated code: output=8d126b9e1d01a434 input=a1aa5d99adfb9656]*/
{
_dbm_state *state = PyType_GetModuleState(cls);
assert(state != NULL);
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