From 67981bbb1587803bb1e029393d2228492cef8c4f Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Sat, 20 Jun 2026 00:28:17 -0700 Subject: [PATCH] tar: ignore nonzero sizes in hard links etc MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Problem reported by Antonio Teixeira. * src/list.c (read_header): When POSIX says a size field must be zero or does not represent a data count, treat it as zero. * tests/extrac32.at: Update to match new behavior. We now treat hard link sizes as zero even when the size fields are nonzero, and this means the “injected” file is treated as valid regardless of whether we list or extract. * tests/extrac34.at: New test. * tests/Makefile.am (TESTSUITE_AT), tests/testsuite.at: Add it. --- NEWS | 7 ++++++- THANKS | 1 + src/list.c | 16 ++++++++++++++++ tests/Makefile.am | 1 + tests/extrac32.at | 2 ++ tests/extrac34.at | 40 ++++++++++++++++++++++++++++++++++++++++ tests/testsuite.at | 1 + 7 files changed, 67 insertions(+), 1 deletion(-) create mode 100644 tests/extrac34.at diff --git a/NEWS b/NEWS index 501cfee3..8e18040d 100644 --- a/NEWS +++ b/NEWS @@ -1,4 +1,4 @@ -GNU tar NEWS - User visible changes. 2026-04-04 +GNU tar NEWS - User visible changes. 2026-06-20 Please send GNU tar bug reports to version 1.35.90 (git) @@ -73,6 +73,11 @@ option. ** tar --ignore-failed-read no longer complains about a file removed before reading. +** tar no longer behaves erratically when reading nonzero size fields + in archive headers representing special files, fifos, and symlinks. + Although these size fields are typically zero, POSIX allows some to + be nonzero, and in practice they do not count data blocks. + * Performance improvements ** Sparse files are now read and written with larger blocksizes. diff --git a/THANKS b/THANKS index 8c5c99d9..fcf35695 100644 --- a/THANKS +++ b/THANKS @@ -39,6 +39,7 @@ Andrey A. Chernov ache@astral.msk.su Andy Gay andy@rdl.co.uk Anthony G. Basile blueness@gentoo.org Antonio Jose Coutinho ajc@di.uminho.pt +Antonio Teixeira antonio.teixeira@suse.com Ariel Faigon ariel@engr.sgi.com Arne Wichmann aw@math.uni-sb.de Arnold Robbins arnold@gnu.org diff --git a/src/list.c b/src/list.c index 5ab6de42..1c992cf4 100644 --- a/src/list.c +++ b/src/list.c @@ -535,6 +535,22 @@ read_header (union block **return_block, struct tar_stat_info *info, struct posix_header const *h = &header->header; char namebuf[sizeof h->prefix + 1 + NAME_FIELD_SIZE + 1]; + switch (h->typeflag) + { + /* For these file types, although POSIX does not specify the + meaning of the size, it does say there should be no data, + so treat the size as zero. */ + case BLKTYPE: case CHRTYPE: case FIFOTYPE: + + /* For these file types, POSIX requires that the size be zero. + Be generous and accept any size as zero, as some + nonconforming programs generate nonzero size fields along + with no data. */ + case LNKTYPE: case SYMTYPE: + + info->stat.st_size = 0; + } + free (recent_long_name); if (next_long_name) diff --git a/tests/Makefile.am b/tests/Makefile.am index 103c6de7..4f666b09 100644 --- a/tests/Makefile.am +++ b/tests/Makefile.am @@ -143,6 +143,7 @@ TESTSUITE_AT = \ extrac31.at\ extrac32.at\ extrac33.at\ + extrac34.at\ filerem01.at\ filerem02.at\ filerem03.at\ diff --git a/tests/extrac32.at b/tests/extrac32.at index d3505fdb..af40916d 100644 --- a/tests/extrac32.at +++ b/tests/extrac32.at @@ -36,11 +36,13 @@ base64 -d < archive.in | xz -c -d > archive.tar AT_CHECK([tar tf archive.tar], [0], [carrier_entry +injected.txt marker.txt ]) AT_CHECK([tar xvf archive.tar], [0], [carrier_entry +injected.txt marker.txt ]) AT_CLEANUP diff --git a/tests/extrac34.at b/tests/extrac34.at new file mode 100644 index 00000000..1cedb463 --- /dev/null +++ b/tests/extrac34.at @@ -0,0 +1,40 @@ +# Check hard link with nonzero size field in tarball. -*- Autotest -*- + +# Copyright 2026 Free Software Foundation, Inc. + +# This file is part of GNU tar. + +# GNU tar is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3 of the License, or +# (at your option) any later version. + +# GNU tar is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. + +# You should have received a copy of the GNU General Public License +# along with this program. If not, see . + +# Check extracting from a nonconforming tarball that has +# a hard link with nonzero size. + +AT_SETUP([hard link with a nonzero size field]) +AT_KEYWORDS([extract extrac34 hard link]) +AT_DATA([archive.in], +[/Td6WFoAAATm1rRGBMBwgFAhARwAAAAAAAAAAAbKrCjgJ/8AaF0AMIAzUBhoiawFdYeRen4lxlj0 +QWRLpUM+28ArRsXVY5bGv4H5kijsqiJ4Z9YIVhZd01+IppF+AkltS60aB8fuUW35Tp/3XzUx9Mq2 +4ypJFzvcgHXsSIvc9L+mmTDuHzhvJQ/oe7ya8QAASbOfD7CgZcIAAYwBgFAAAEWxohaxxGf7AgAA +AAAEWVo= +]) +AT_CHECK([base64 --help >/dev/null 2>&1 || AT_SKIP_TEST +xz --help >/dev/null 2>&1 || AT_SKIP_TEST +base64 -d < archive.in | xz -c -d > archive.tar +]) +AT_CHECK([mkdir dir +]) +AT_CHECK([tar -C dir -xf archive.tar || exit 1 +cmp dir/a dir/b +]) +AT_CLEANUP diff --git a/tests/testsuite.at b/tests/testsuite.at index 70d36a5a..ab30c2ab 100644 --- a/tests/testsuite.at +++ b/tests/testsuite.at @@ -360,6 +360,7 @@ m4_include([extrac30.at]) m4_include([extrac31.at]) m4_include([extrac32.at]) m4_include([extrac33.at]) +m4_include([extrac34.at]) m4_include([backup01.at])