From: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>
Date: Fri, 24 Jan 2020 20:10:42 +0000 (-0800)
Subject: bpo-39430: Fix race condition in lazy imports in tarfile. (GH-18161)
X-Git-Tag: v3.8.2rc1~45
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=ea4a61fec842c94107eef46e5030b89a086f94bb;p=thirdparty%2FPython%2Fcpython.git

bpo-39430: Fix race condition in lazy imports in tarfile. (GH-18161)


Use `from ... import ...` to ensure module is fully loaded before accessing its attributes.
(cherry picked from commit 9017e0bd5e124ae6d2ed94b9e9cacb2e86270980)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
---

diff --git a/Lib/tarfile.py b/Lib/tarfile.py
index 2c06f9160c65..d31b9cbb51d6 100755
--- a/Lib/tarfile.py
+++ b/Lib/tarfile.py
@@ -1655,13 +1655,12 @@ class TarFile(object):
             raise ValueError("mode must be 'r', 'w' or 'x'")
 
         try:
-            import gzip
-            gzip.GzipFile
-        except (ImportError, AttributeError):
+            from gzip import GzipFile
+        except ImportError:
             raise CompressionError("gzip module is not available")
 
         try:
-            fileobj = gzip.GzipFile(name, mode + "b", compresslevel, fileobj)
+            fileobj = GzipFile(name, mode + "b", compresslevel, fileobj)
         except OSError:
             if fileobj is not None and mode == 'r':
                 raise ReadError("not a gzip file")
@@ -1689,12 +1688,11 @@ class TarFile(object):
             raise ValueError("mode must be 'r', 'w' or 'x'")
 
         try:
-            import bz2
+            from bz2 import BZ2File
         except ImportError:
             raise CompressionError("bz2 module is not available")
 
-        fileobj = bz2.BZ2File(fileobj or name, mode,
-                              compresslevel=compresslevel)
+        fileobj = BZ2File(fileobj or name, mode, compresslevel=compresslevel)
 
         try:
             t = cls.taropen(name, mode, fileobj, **kwargs)
@@ -1718,15 +1716,15 @@ class TarFile(object):
             raise ValueError("mode must be 'r', 'w' or 'x'")
 
         try:
-            import lzma
+            from lzma import LZMAFile, LZMAError
         except ImportError:
             raise CompressionError("lzma module is not available")
 
-        fileobj = lzma.LZMAFile(fileobj or name, mode, preset=preset)
+        fileobj = LZMAFile(fileobj or name, mode, preset=preset)
 
         try:
             t = cls.taropen(name, mode, fileobj, **kwargs)
-        except (lzma.LZMAError, EOFError):
+        except (LZMAError, EOFError):
             fileobj.close()
             if mode == 'r':
                 raise ReadError("not an lzma file")
diff --git a/Misc/NEWS.d/next/Library/2020-01-24-11-05-21.bpo-39430.I0UQzM.rst b/Misc/NEWS.d/next/Library/2020-01-24-11-05-21.bpo-39430.I0UQzM.rst
new file mode 100644
index 000000000000..712fc5d34bbe
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-01-24-11-05-21.bpo-39430.I0UQzM.rst
@@ -0,0 +1 @@
+Fixed race condition in lazy imports in :mod:`tarfile`.