Ripduman Sohan wrote:
> There's a subtle bug in gzip (1.3.13) decompression when no suffixes
> are employed.
>
> The command [gzip -d -S "" <infile>] will, as expected, ask to
> overwrite the output file. However, it goes on to unlink the newly
> created (decompressed file) resulting in data loss through file deletion.
Thanks again.
FYI, here are two more patches to exercise the bug:
-- tests: add ---presume-input-tty option, solely for testing
(note the three hyphens)
-- tests: exercise the fix for the decompression data-loss bug
>From bd0c4e025575180648388b63e7b69c6341fbd892 Mon Sep 17 00:00:00 2001
From: Jim Meyering <meyer...@redhat.com>
Date: Fri, 19 Feb 2010 20:52:04 +0100
Subject: [PATCH 1/2] tests: add ---presume-input-tty option, solely for testing
* gzip.c: Include <stdbool.h>.
(presume_input_tty): New global.
(main): Set it.
(treat_stdin, check_ofname): Use it.
---
gzip.c | 25 +++++++++++++++++++++----
1 files changed, 21 insertions(+), 4 deletions(-)
diff --git a/gzip.c b/gzip.c
index 141397e..8f36bcc 100644
--- a/gzip.c
+++ b/gzip.c
@@ -29,7 +29,7 @@
*/
static char const *const license_msg[] = {
-"Copyright (C) 2007 Free Software Foundation, Inc.",
+"Copyright (C) 2007, 2010 Free Software Foundation, Inc.",
"Copyright (C) 1993 Jean-loup Gailly.",
"This is free software. You may redistribute copies of it under the terms of",
"the GNU General Public License <http://www.gnu.org/licenses/gpl.html>.",
@@ -58,6 +58,7 @@ static char const *const license_msg[] = {
#include <ctype.h>
#include <sys/types.h>
#include <signal.h>
+#include <stdbool.h>
#include <sys/stat.h>
#include <errno.h>
@@ -167,6 +168,10 @@ DECLARE(uch, window, 2L*WSIZE);
/* local variables */
+/* If true, pretend that standard input is a tty. This option
+ is deliberately not documented, and only for testing. */
+static bool presume_input_tty;
+
int ascii = 0; /* convert end-of-lines to local OS conventions */
int to_stdout = 0; /* output to stdout (-c) */
int decompress = 0; /* decompress (-d) */
@@ -243,6 +248,13 @@ static int handled_sig[] =
#endif
};
+/* For long options that have no equivalent short option, use a
+ non-character as a pseudo short option, starting with CHAR_MAX + 1. */
+enum
+{
+ PRESUME_INPUT_TTY_OPTION = CHAR_MAX + 1
+};
+
struct option longopts[] =
{
/* { name has_arg *flag val } */
@@ -259,6 +271,7 @@ struct option longopts[] =
{"license", 0, 0, 'L'}, /* display software license */
{"no-name", 0, 0, 'n'}, /* don't save or restore original name & time */
{"name", 0, 0, 'N'}, /* save or restore original name & time */
+ {"-presume-input-tty", no_argument, NULL, PRESUME_INPUT_TTY_OPTION},
{"quiet", 0, 0, 'q'}, /* quiet mode */
{"silent", 0, 0, 'q'}, /* quiet mode */
{"recursive", 0, 0, 'r'}, /* recurse through directories */
@@ -271,6 +284,7 @@ struct option longopts[] =
{"best", 0, 0, '9'}, /* compress better */
{"lzw", 0, 0, 'Z'}, /* make output compatible with old compress */
{"bits", 1, 0, 'b'}, /* max number of bits per code (implies -Z) */
+
{ 0, 0, 0, 0 }
};
@@ -468,6 +482,8 @@ int main (int argc, char **argv)
no_name = no_time = 1; break;
case 'N':
no_name = no_time = 0; break;
+ case PRESUME_INPUT_TTY_OPTION:
+ presume_input_tty = true; break;
case 'q':
quiet = 1; verbose = 0; break;
case 'r':
@@ -591,8 +607,9 @@ input_eof ()
*/
local void treat_stdin()
{
- if (!force && !list &&
- isatty(fileno((FILE *)(decompress ? stdin : stdout)))) {
+ if (!force && !list
+ && (presume_input_tty
+ || isatty(fileno((FILE *)(decompress ? stdin : stdout))))) {
/* Do not send compressed data to the terminal or read it from
* the terminal. We get here when user invoked the program
* without parameters, so be helpful. According to the GNU standards:
@@ -1617,7 +1634,7 @@ local int check_ofname()
if (!force) {
int ok = 0;
fprintf (stderr, "%s: %s already exists;", program_name, ofname);
- if (foreground && isatty(fileno(stdin))) {
+ if (foreground && (presume_input_tty || isatty(fileno(stdin)))) {
fprintf(stderr, " do you wish to overwrite (y or n)? ");
fflush(stderr);
ok = yesno();
--
1.7.0.233.g05e1a
>From fa627092978b0099297581eb90f09c7ecffc157b Mon Sep 17 00:00:00 2001
From: Jim Meyering <meyer...@redhat.com>
Date: Fri, 19 Feb 2010 20:50:09 +0100
Subject: [PATCH 2/2] tests: exercise the fix for the decompression data-loss bug
* tests/null-suffix-clobber: New file.
* Makefile.am (TESTS): Add it.
---
Makefile.am | 1 +
tests/null-suffix-clobber | 41 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 42 insertions(+), 0 deletions(-)
create mode 100755 tests/null-suffix-clobber
diff --git a/Makefile.am b/Makefile.am
index 816e9f4..3b048b8 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -108,6 +108,7 @@ TESTS = \
tests/hufts \
tests/memcpy-abuse \
tests/mixed \
+ tests/null-suffix-clobber \
tests/stdin \
tests/trailing-nul \
tests/zdiff \
diff --git a/tests/null-suffix-clobber b/tests/null-suffix-clobber
new file mode 100755
index 0000000..e5b52a1
--- /dev/null
+++ b/tests/null-suffix-clobber
@@ -0,0 +1,41 @@
+#!/bin/sh
+# Before gzip-1.5, gzip -d -S '' k.gz would delete F.gz and not create "F"
+
+# Copyright (C) 2010 Free Software Foundation, Inc.
+
+# This program 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.
+
+# This program 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 <http://www.gnu.org/licenses/>.
+# limit so don't run it by default.
+
+if test "$VERBOSE" = yes; then
+ set -x
+ gzip --version
+fi
+
+: ${srcdir=.}
+. "$srcdir/tests/init.sh"
+
+printf anything | gzip > F.gz || framework_failure
+echo y > yes || framework_failure
+echo "gzip: invalid suffix ''" > expected-err || framework_failure
+
+fail=0
+
+gzip ---presume-input-tty -d -S '' F.gz < yes > out 2>err && fail=1
+
+compare out /dev/null || fail=1
+compare err expected-err || fail=1
+
+test -f F.gz || fail=1
+
+Exit $fail
--
1.7.0.233.g05e1a
