From: Ma Lin <animalize@users.noreply.github.com>
Date: Mon, 26 Apr 2021 19:50:33 +0000 (+0800)
Subject: Fix thread locks in zlib module may go wrong in rare case (#22130)
X-Git-Tag: v3.9.5~34
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=ba7338a46038bdb55159bf37e7ad83f177e5257b;p=thirdparty%2FPython%2Fcpython.git

Fix thread locks in zlib module may go wrong in rare case (#22130)

Setting `next_in` before acquiring the thread lock may mix up compress/decompress state in other threads.
---

diff --git a/Misc/NEWS.d/next/Library/2020-09-07-21-40-07.bpo-41735.NKqGKy.rst b/Misc/NEWS.d/next/Library/2020-09-07-21-40-07.bpo-41735.NKqGKy.rst
new file mode 100644
index 000000000000..9e36435a364e
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-09-07-21-40-07.bpo-41735.NKqGKy.rst
@@ -0,0 +1 @@
+Fix thread locks in zlib module may go wrong in rare case. Patch by Ma Lin.
diff --git a/Modules/zlibmodule.c b/Modules/zlibmodule.c
index fe27909ae8a7..6c14c3adbf26 100644
--- a/Modules/zlibmodule.c
+++ b/Modules/zlibmodule.c
@@ -667,11 +667,11 @@ zlib_Compress_compress_impl(compobject *self, Py_buffer *data)
     Py_ssize_t ibuflen, obuflen = DEF_BUF_SIZE;
     int err;
 
+    ENTER_ZLIB(self);
+
     self->zst.next_in = data->buf;
     ibuflen = data->len;
 
-    ENTER_ZLIB(self);
-
     do {
         arrange_input_buffer(&self->zst, &ibuflen);
 
@@ -785,6 +785,8 @@ zlib_Decompress_decompress_impl(compobject *self, Py_buffer *data,
     else
         hard_limit = max_length;
 
+    ENTER_ZLIB(self);
+
     self->zst.next_in = data->buf;
     ibuflen = data->len;
 
@@ -792,8 +794,6 @@ zlib_Decompress_decompress_impl(compobject *self, Py_buffer *data,
     if (max_length && obuflen > max_length)
         obuflen = max_length;
 
-    ENTER_ZLIB(self);
-
     do {
         arrange_input_buffer(&self->zst, &ibuflen);