From c250d10145d6ca61bf104c3475ccab78be5585bd Mon Sep 17 00:00:00 2001 From: Petr Viktorin Date: Tue, 16 Jun 2026 16:04:10 +0200 Subject: [PATCH 1/5] Break loop at EOF --- Lib/tarfile.py | 4 +++- Lib/test/test_tarfile.py | 16 ++++++++++++++++ 2 files changed, 19 insertions(+), 1 deletion(-) diff --git a/Lib/tarfile.py b/Lib/tarfile.py index a293a049247274..c947492d40a200 100644 --- a/Lib/tarfile.py +++ b/Lib/tarfile.py @@ -520,7 +520,9 @@ def seek(self, pos=0): if pos - self.pos >= 0: blocks, remainder = divmod(pos - self.pos, self.bufsize) for i in range(blocks): - self.read(self.bufsize) + size = self.read(self.bufsize) + if not size: + break self.read(remainder) else: raise StreamError("seeking backwards is not allowed") diff --git a/Lib/test/test_tarfile.py b/Lib/test/test_tarfile.py index 62a262740a7efa..e19df43718f414 100644 --- a/Lib/test/test_tarfile.py +++ b/Lib/test/test_tarfile.py @@ -4831,6 +4831,22 @@ def valueerror_filter(tarinfo, path): with self.check_context(arc.open(errorlevel='boo!'), filtererror_filter): self.expect_exception(TypeError) # errorlevel is not int + @support.subTests('format', [tarfile.GNU_FORMAT, tarfile.PAX_FORMAT]) + def test_getmembers_big_size(self, format): + # gh-NNNNN: A loop in seek() for streaming files tried to read the + # declared number of blocks even at EOF + tinfo = tarfile.TarInfo("huge-file") + tinfo.size = 1 << 64 + bio = io.BytesIO() + # Write header without data + bio.write(tinfo.tobuf(format)) + + # Reset & try to get contents + bio.seek(0) + with tarfile.open(fileobj=bio, mode="r|") as tar: + with self.assertRaises(tarfile.ReadError): + tar.getmembers() + class OverwriteTests(archiver_tests.OverwriteTests, unittest.TestCase): testdir = os.path.join(TEMPDIR, "testoverwrite") From 38d6c4f628f8bf0ac238ef1a7381280a9fbbc1fe Mon Sep 17 00:00:00 2001 From: Petr Viktorin Date: Tue, 23 Jun 2026 13:23:44 +0200 Subject: [PATCH 2/5] Assign issue number --- Lib/test/test_tarfile.py | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/Lib/test/test_tarfile.py b/Lib/test/test_tarfile.py index eb7ac0115f5896..fd6e3ce9654618 100644 --- a/Lib/test/test_tarfile.py +++ b/Lib/test/test_tarfile.py @@ -4880,7 +4880,7 @@ def valueerror_filter(tarinfo, path): @support.subTests('format', [tarfile.GNU_FORMAT, tarfile.PAX_FORMAT]) def test_getmembers_big_size(self, format): - # gh-NNNNN: A loop in seek() for streaming files tried to read the + # gh-151981: A loop in seek() for streaming files tried to read the # declared number of blocks even at EOF tinfo = tarfile.TarInfo("huge-file") tinfo.size = 1 << 64 From 0d5ceb5708acc78e5f0cebc96a27942120b34f69 Mon Sep 17 00:00:00 2001 From: Petr Viktorin Date: Tue, 23 Jun 2026 13:28:18 +0200 Subject: [PATCH 3/5] Add a blurb --- .../next/Library/2026-06-23-13-28-16.gh-issue-151981.xBHEcU.rst | 2 ++ 1 file changed, 2 insertions(+) create mode 100644 Misc/NEWS.d/next/Library/2026-06-23-13-28-16.gh-issue-151981.xBHEcU.rst diff --git a/Misc/NEWS.d/next/Library/2026-06-23-13-28-16.gh-issue-151981.xBHEcU.rst b/Misc/NEWS.d/next/Library/2026-06-23-13-28-16.gh-issue-151981.xBHEcU.rst new file mode 100644 index 00000000000000..2123ab8e081b1d --- /dev/null +++ b/Misc/NEWS.d/next/Library/2026-06-23-13-28-16.gh-issue-151981.xBHEcU.rst @@ -0,0 +1,2 @@ +In :mod:`tarfile`, seeking a stream now stops when end of the stream is +reached. From 49dac62b78a55efdbf75fb6585d803ab7a8c8301 Mon Sep 17 00:00:00 2001 From: Petr Viktorin Date: Tue, 23 Jun 2026 14:11:17 +0200 Subject: [PATCH 4/5] Move to Security --- .../2026-06-23-13-28-16.gh-issue-151981.xBHEcU.rst | 0 1 file changed, 0 insertions(+), 0 deletions(-) rename Misc/NEWS.d/next/{Library => Security}/2026-06-23-13-28-16.gh-issue-151981.xBHEcU.rst (100%) diff --git a/Misc/NEWS.d/next/Library/2026-06-23-13-28-16.gh-issue-151981.xBHEcU.rst b/Misc/NEWS.d/next/Security/2026-06-23-13-28-16.gh-issue-151981.xBHEcU.rst similarity index 100% rename from Misc/NEWS.d/next/Library/2026-06-23-13-28-16.gh-issue-151981.xBHEcU.rst rename to Misc/NEWS.d/next/Security/2026-06-23-13-28-16.gh-issue-151981.xBHEcU.rst From 4a5cbce3dcd36b4a80819e295d534edb3b02d135 Mon Sep 17 00:00:00 2001 From: Petr Viktorin Date: Tue, 23 Jun 2026 14:11:54 +0200 Subject: [PATCH 5/5] Update Lib/tarfile.py Co-authored-by: Stan Ulbrych --- Lib/tarfile.py | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/Lib/tarfile.py b/Lib/tarfile.py index fb5f71025e4832..58061b3e8c1ca4 100644 --- a/Lib/tarfile.py +++ b/Lib/tarfile.py @@ -546,8 +546,8 @@ def seek(self, pos=0): if pos - self.pos >= 0: blocks, remainder = divmod(pos - self.pos, self.bufsize) for i in range(blocks): - size = self.read(self.bufsize) - if not size: + data = self.read(self.bufsize) + if not data: break self.read(remainder) else: