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.
>
> I believe the attached patch should solve this problem.
Thanks a lot for reporting that and writing a patch.
I've taken a slightly different approach to fixing it:
don't accept -S '' ever.
And don't recommend using gunzip -S '' in the documentation.
>From 00d2c126d60bae3bdf1a64e3fcc70355dee8f475 Mon Sep 17 00:00:00 2001
From: Jim Meyering <meyer...@redhat.com>
Date: Sat, 20 Feb 2010 11:07:55 +0100
Subject: [PATCH] gzip: fix a data-loss bug when decompressing with --suffix=''
* gzip.c (main): Disallow an empty --suffix=S also with -d.
Otherwise, "gzip -d -S '' F.gz" would ask if it's ok to remove the
existing file, "F.gz"; if you reply "yes", you'd lose all of that data.
Use of an empty suffix was already rejected in compression mode.
* gzip.1 (--suffix (-S)): Do not recommend to use "gunzip -S '' *".
Describe how the suffix is used when decompressing, too.
* NEWS (Bug fixes): mention the fix.
Reported by Ripduman Sohan.
---
NEWS | 6 ++++++
THANKS | 1 +
gzip.1 | 11 +++++------
gzip.c | 6 +++---
4 files changed, 15 insertions(+), 9 deletions(-)
diff --git a/NEWS b/NEWS
index 9c248f1..7a98c49 100644
--- a/NEWS
+++ b/NEWS
@@ -4,6 +4,12 @@ GNU gzip NEWS -*- outline
-*-
** Bug fixes
+ "gzip -d -S '' precious.gz" is now rejected immediately. Before,
+ that command would emulate "rm -i precious.gz", but with an easily-
+ misunderstood prompt. I.e., gzip would ask if it's ok to remove the
+ existing file, "precious.gz". If you made the mistake of saying "yes",
+ it would remove that input file before attempting to uncompress it.
+
gzip -cdf now properly handles input consisting of gzip'd data followed
by uncompressed data. Before it would output raw compressed input, too.
For example, now "(printf x|gzip; echo y)|gzip -dcf" prints "xy\n",
diff --git a/THANKS b/THANKS
index 183d39c..b0833e5 100644
--- a/THANKS
+++ b/THANKS
@@ -237,6 +237,7 @@ Amos Shapira am...@cs.huji.ac.il
Rick Sladkey j...@world.std.com
Daniel L Smith d...@autodesk.com
Fred Smith fredex%fcsh...@merk.merk.com
+Ripduman Sohan ripduman.so...@cl.cam.ac.uk
Stephen Soliday soli...@ncat.edu
Paul Southworth pa...@css.itd.umich.edu
Rob Spencer rob...@winkle.bhpese.oz.au
diff --git a/gzip.1 b/gzip.1
index bdf6943..8db327d 100644
--- a/gzip.1
+++ b/gzip.1
@@ -291,15 +291,14 @@ will descend into the directory and compress all the
files it finds there
).
.TP
.B \-S .suf --suffix .suf
-Use suffix .suf instead of .gz. Any suffix can be given, but suffixes
+When compressing, use suffix .suf instead of .gz.
+Any non-empty suffix can be given, but suffixes
other than .z and .gz should be avoided to avoid confusion when files
-are transferred to other systems. A null suffix forces gunzip to try
-decompression on all given files regardless of suffix, as in:
+are transferred to other systems.
- gunzip -S "" * (*.* for MSDOS)
+When decompressing, add .suf to the beginning of the list of
+suffixes to try, when deriving an output file name from an input file name.
-Previous versions of gzip used
-the .z suffix. This was changed to avoid a conflict with
.IR pack "(1)".
.TP
.B \-t --test
diff --git a/gzip.c b/gzip.c
index 8f36bcc..9d893b3 100644
--- a/gzip.c
+++ b/gzip.c
@@ -543,11 +543,11 @@ int main (int argc, char **argv)
program_name);
}
#endif
- if ((z_len == 0 && !decompress) || z_len > MAX_SUFFIX) {
- fprintf(stderr, "%s: incorrect suffix '%s'\n",
- program_name, z_suffix);
+ if (z_len == 0 || z_len > MAX_SUFFIX) {
+ fprintf(stderr, "%s: invalid suffix '%s'\n", program_name, z_suffix);
do_exit(ERROR);
}
+
if (do_lzw && !decompress) work = lzw;
/* Allocate all global buffers (for DYN_ALLOC option) */
--
1.7.0.233.g05e1a
