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bpo-40826: Fix GIL usage in PyOS_Readline() #20579

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Merged
merged 1 commit into from
Jun 1, 2020
Merged

bpo-40826: Fix GIL usage in PyOS_Readline() #20579

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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core and Builtins/2020-06-01-20-31-07.bpo-40826.XCI4M2.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Fix GIL usage in :c:func:`PyOS_Readline`: lock the GIL to set an exception.
101 changes: 72 additions & 29 deletions Parser/myreadline.c
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Original file line number Diff line number Diff line change
Expand Up @@ -27,22 +27,24 @@ int (*PyOS_InputHook)(void) = NULL;
except if PyOS_InterruptOccurred() returns true. */

static int
my_fgets(char *buf, int len, FILE *fp)
my_fgets(PyThreadState* tstate, char *buf, int len, FILE *fp)
{
#ifdef MS_WINDOWS
HANDLE hInterruptEvent;
#endif
char *p;
int err;
while (1) {
if (PyOS_InputHook != NULL)
if (PyOS_InputHook != NULL) {
(void)(PyOS_InputHook)();
}

errno = 0;
clearerr(fp);
p = fgets(buf, len, fp);
if (p != NULL)
char *p = fgets(buf, len, fp);
if (p != NULL) {
return 0; /* No error */
err = errno;
}
int err = errno;

#ifdef MS_WINDOWS
/* Ctrl-C anywhere on the line or Ctrl-Z if the only character
on a line will set ERROR_OPERATION_ABORTED. Under normal
Expand All @@ -68,22 +70,26 @@ my_fgets(char *buf, int len, FILE *fp)
}
}
#endif /* MS_WINDOWS */

if (feof(fp)) {
clearerr(fp);
return -1; /* EOF */
}

#ifdef EINTR
if (err == EINTR) {
int s;
PyEval_RestoreThread(_PyOS_ReadlineTState);
s = PyErr_CheckSignals();
PyEval_RestoreThread(tstate);
int s = PyErr_CheckSignals();
PyEval_SaveThread();
if (s < 0)
return 1;
/* try again */

if (s < 0) {
return 1;
}
/* try again */
continue;
}
#endif

if (PyOS_InterruptOccurred()) {
return 1; /* Interrupt */
}
Expand All @@ -98,7 +104,7 @@ my_fgets(char *buf, int len, FILE *fp)
extern char _get_console_type(HANDLE handle);

char *
_PyOS_WindowsConsoleReadline(HANDLE hStdIn)
_PyOS_WindowsConsoleReadline(PyThreadState *tstate, HANDLE hStdIn)
{
static wchar_t wbuf_local[1024 * 16];
const DWORD chunk_size = 1024;
Expand Down Expand Up @@ -133,11 +139,12 @@ _PyOS_WindowsConsoleReadline(HANDLE hStdIn)
if (WaitForSingleObjectEx(hInterruptEvent, 100, FALSE)
== WAIT_OBJECT_0) {
ResetEvent(hInterruptEvent);
PyEval_RestoreThread(_PyOS_ReadlineTState);
PyEval_RestoreThread(tstate);
s = PyErr_CheckSignals();
PyEval_SaveThread();
if (s < 0)
if (s < 0) {
goto exit;
}
}
break;
}
Expand All @@ -150,17 +157,22 @@ _PyOS_WindowsConsoleReadline(HANDLE hStdIn)
if (wbuf == wbuf_local) {
wbuf[total_read] = '\0';
wbuf = (wchar_t*)PyMem_RawMalloc(wbuflen * sizeof(wchar_t));
if (wbuf)
if (wbuf) {
wcscpy_s(wbuf, wbuflen, wbuf_local);
}
else {
PyEval_RestoreThread(tstate);
PyErr_NoMemory();
PyEval_SaveThread();
goto exit;
}
}
else {
wchar_t *tmp = PyMem_RawRealloc(wbuf, wbuflen * sizeof(wchar_t));
if (tmp == NULL) {
PyEval_RestoreThread(tstate);
PyErr_NoMemory();
PyEval_SaveThread();
goto exit;
}
wbuf = tmp;
Expand All @@ -169,33 +181,45 @@ _PyOS_WindowsConsoleReadline(HANDLE hStdIn)

if (wbuf[0] == '\x1a') {
buf = PyMem_RawMalloc(1);
if (buf)
if (buf) {
buf[0] = '\0';
}
else {
PyEval_RestoreThread(tstate);
PyErr_NoMemory();
PyEval_SaveThread();
}
goto exit;
}

u8len = WideCharToMultiByte(CP_UTF8, 0, wbuf, total_read, NULL, 0, NULL, NULL);
u8len = WideCharToMultiByte(CP_UTF8, 0,
wbuf, total_read,
NULL, 0,
NULL, NULL);
buf = PyMem_RawMalloc(u8len + 1);
if (buf == NULL) {
PyEval_RestoreThread(tstate);
PyErr_NoMemory();
PyEval_SaveThread();
goto exit;
}
u8len = WideCharToMultiByte(CP_UTF8, 0, wbuf, total_read, buf, u8len, NULL, NULL);

u8len = WideCharToMultiByte(CP_UTF8, 0,
wbuf, total_read,
buf, u8len,
NULL, NULL);
buf[u8len] = '\0';

exit:
if (wbuf != wbuf_local)
if (wbuf != wbuf_local) {
PyMem_RawFree(wbuf);
}

if (err) {
PyEval_RestoreThread(_PyOS_ReadlineTState);
PyEval_RestoreThread(tstate);
PyErr_SetFromWindowsErr(err);
PyEval_SaveThread();
}

return buf;
}

Expand All @@ -209,6 +233,8 @@ PyOS_StdioReadline(FILE *sys_stdin, FILE *sys_stdout, const char *prompt)
{
size_t n;
char *p, *pr;
PyThreadState *tstate = _PyOS_ReadlineTState;
assert(tstate != NULL);

#ifdef MS_WINDOWS
if (!Py_LegacyWindowsStdioFlag && sys_stdin == stdin) {
Expand All @@ -230,7 +256,9 @@ PyOS_StdioReadline(FILE *sys_stdin, FILE *sys_stdout, const char *prompt)
if (wlen) {
wbuf = PyMem_RawMalloc(wlen * sizeof(wchar_t));
if (wbuf == NULL) {
PyEval_RestoreThread(tstate);
PyErr_NoMemory();
PyEval_SaveThread();
return NULL;
}
wlen = MultiByteToWideChar(CP_UTF8, 0, prompt, -1,
Expand All @@ -249,24 +277,27 @@ PyOS_StdioReadline(FILE *sys_stdin, FILE *sys_stdout, const char *prompt)
}
}
clearerr(sys_stdin);
return _PyOS_WindowsConsoleReadline(hStdIn);
return _PyOS_WindowsConsoleReadline(tstate, hStdIn);
}
}
#endif

n = 100;
p = (char *)PyMem_RawMalloc(n);
if (p == NULL) {
PyEval_RestoreThread(tstate);
PyErr_NoMemory();
PyEval_SaveThread();
return NULL;
}

fflush(sys_stdout);
if (prompt)
if (prompt) {
fprintf(stderr, "%s", prompt);
}
fflush(stderr);

switch (my_fgets(p, (int)n, sys_stdin)) {
switch (my_fgets(tstate, p, (int)n, sys_stdin)) {
case 0: /* Normal case */
break;
case 1: /* Interrupt */
Expand All @@ -278,29 +309,40 @@ PyOS_StdioReadline(FILE *sys_stdin, FILE *sys_stdout, const char *prompt)
*p = '\0';
break;
}

n = strlen(p);
while (n > 0 && p[n-1] != '\n') {
size_t incr = n+2;
if (incr > INT_MAX) {
PyMem_RawFree(p);
PyEval_RestoreThread(tstate);
PyErr_SetString(PyExc_OverflowError, "input line too long");
PyEval_SaveThread();
return NULL;
}

pr = (char *)PyMem_RawRealloc(p, n + incr);
if (pr == NULL) {
PyMem_RawFree(p);
PyEval_RestoreThread(tstate);
PyErr_NoMemory();
PyEval_SaveThread();
return NULL;
}
p = pr;
if (my_fgets(p+n, (int)incr, sys_stdin) != 0)

if (my_fgets(tstate, p+n, (int)incr, sys_stdin) != 0) {
break;
}
n += strlen(p+n);
}

pr = (char *)PyMem_RawRealloc(p, n+1);
if (pr == NULL) {
PyMem_RawFree(p);
PyEval_RestoreThread(tstate);
PyErr_NoMemory();
PyEval_SaveThread();
return NULL;
}
return pr;
Expand All @@ -323,7 +365,8 @@ PyOS_Readline(FILE *sys_stdin, FILE *sys_stdout, const char *prompt)
char *rv, *res;
size_t len;

if (_PyOS_ReadlineTState == _PyThreadState_GET()) {
PyThreadState *tstate = _PyThreadState_GET();
if (_PyOS_ReadlineTState == tstate) {
PyErr_SetString(PyExc_RuntimeError,
"can't re-enter readline");
return NULL;
Expand All @@ -342,7 +385,7 @@ PyOS_Readline(FILE *sys_stdin, FILE *sys_stdout, const char *prompt)
}
}

_PyOS_ReadlineTState = _PyThreadState_GET();
_PyOS_ReadlineTState = tstate;
Py_BEGIN_ALLOW_THREADS
PyThread_acquire_lock(_PyOS_ReadlineLock, 1);

Expand Down