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Fix thread locks in zlib module may go wrong in rare case. (#22126)

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Setting `next_in` before acquiring the thread lock may mix up compress/decompress state in other threads.
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Ma Lin 2021-04-27 16:37:11 +08:00 committed by GitHub
parent 878bc8b6c2
commit 93f411838a
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GPG key ID: 4AEE18F83AFDEB23
2 changed files with 11 additions and 9 deletions
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1
Misc/NEWS.d/next/Library/2020-09-07-11-15-15.bpo-41735.NKqGKy.rst Normal file
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@ -0,0 +1 @@
Fix thread locks in zlib module may go wrong in rare case. Patch by Ma Lin.

19
Modules/zlibmodule.c
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@ -10,10 +10,12 @@
#include "zlib.h"
#define ENTER_ZLIB(obj) \
Py_BEGIN_ALLOW_THREADS; \
PyThread_acquire_lock((obj)->lock, 1); \
Py_END_ALLOW_THREADS;
#define ENTER_ZLIB(obj) do { \
if (!PyThread_acquire_lock((obj)->lock, 0)) { \
Py_BEGIN_ALLOW_THREADS \
PyThread_acquire_lock((obj)->lock, 1); \
Py_END_ALLOW_THREADS \
} } while (0)
#define LEAVE_ZLIB(obj) PyThread_release_lock((obj)->lock);
#if defined(ZLIB_VERNUM) && ZLIB_VERNUM >= 0x1221
@ -634,14 +636,13 @@ zlib_Compress_compress_impl(compobject *self, PyTypeObject *cls,
PyObject *RetVal = NULL;
Py_ssize_t obuflen = DEF_BUF_SIZE;
int err;
zlibstate *state = PyType_GetModuleState(cls);
ENTER_ZLIB(self);
self->zst.next_in = data->buf;
Py_ssize_t ibuflen = data->len;
ENTER_ZLIB(self);
do {
arrange_input_buffer(&self->zst, &ibuflen);
@ -761,6 +762,8 @@ zlib_Decompress_decompress_impl(compobject *self, PyTypeObject *cls,
else
hard_limit = max_length;
ENTER_ZLIB(self);
self->zst.next_in = data->buf;
ibuflen = data->len;
@ -768,8 +771,6 @@ zlib_Decompress_decompress_impl(compobject *self, PyTypeObject *cls,
if (max_length && obuflen > max_length)
obuflen = max_length;
ENTER_ZLIB(self);
do {
arrange_input_buffer(&self->zst, &ibuflen);