On 2020-12-28 Sebastian Andrzej Siewior wrote:
> xz refuses to decompress a file which has more than one hard link. It
> can be reproduced by (as per Vincent):
> |$ echo foo > file1
> |$ xz file1
> |$ ln file1.xz file2.xz
> |$ xz -dk file1.xz
> |xz: file1.xz: Input file has more than one hard link, skipping
>
> This behaviour is consistent with `gzip' and `bzip2' but it is not
> documented. The `--force' option would ignore this restriction.
The behavior is documented on the xz man page:
Unless writing to standard output, xz will display a warning
and skip the file if any of the following applies:
o File is not a regular file. Symbolic links are not followed,
and thus they are not considered to be regular files.
o File has more than one hard link.
o File has setuid, setgid, or sticky bit set.
The reason why it's done is indeed missing. I don't have any better
guesses than what you already listed in other messages.
> Ignore hard link count on input.
I'm fine with the patch since the suggested behavior makes sense to me
too. There's always a risk that some specific use case can break due to
this change but I guess that is acceptably low risk.
I wonder if it were more logical if --keep also allowed processing of
files with setuid, setgid, or sticky bit set. The same reasoning
applies to all these cases, I suppose, and they are all within the same
if-block in the code so it would still be a single-line change.
What about symlinks or files that aren't regular files (like block
devices)? I guess requiring --force for non-regular files makes sense
still but perhaps symlinks that point to regular files are OK to
process with --keep.
Any thoughts on this patch?
diff --git a/src/xz/file_io.c b/src/xz/file_io.c
index e1a37d5..80b56d3 100644
--- a/src/xz/file_io.c
+++ b/src/xz/file_io.c
@@ -536,8 +536,9 @@ io_open_src_real(file_pair *pair)
}
// Symlinks are not followed unless writing to stdout or --force
- // was used.
- const bool follow_symlinks = opt_stdout || opt_force;
+ // or --keep was used.
+ const bool follow_symlinks
+ = opt_stdout || opt_force || opt_keep_original;
// We accept only regular files if we are writing the output
// to disk too. bzip2 allows overriding this with --force but
@@ -674,7 +675,7 @@ io_open_src_real(file_pair *pair)
}
#ifndef TUKLIB_DOSLIKE
- if (reg_files_only && !opt_force) {
+ if (reg_files_only && !opt_force && !opt_keep_original) {
if (pair->src_st.st_mode & (S_ISUID | S_ISGID)) {
// gzip rejects setuid and setgid files even
// when --force was used. bzip2 doesn't check
@@ -683,7 +684,7 @@ io_open_src_real(file_pair *pair)
// and setgid bits there.
//
// We accept setuid and setgid files if
- // --force was used. We drop these bits
+ // --force or --keep was used. We drop these bits
// explicitly in io_copy_attr().
message_warning(_("%s: File has setuid or "
"setgid bit set, skipping"),
diff --git a/src/xz/xz.1 b/src/xz/xz.1
index db9de4f..e50e762 100644
--- a/src/xz/xz.1
+++ b/src/xz/xz.1
@@ -392,6 +392,20 @@ should be used.
.TP
.BR \-k ", " \-\-keep
Don't delete the input files.
+.IP ""
+Since
+.B xz
+5.4.0,
+this option also makes
+.B xz
+compress or decompress even if the input is
+a symbolic link to a regular file,
+has more than one hard link,
+or has the setuid, setgid, or sticky bit set.
+The setuid, setgid, and sticky bits are not copied
+to the target file.
+In earlier versions this was only done with
+.BR \-\-force .
.TP
.BR \-f ", " \-\-force
This option has several effects:
--
Lasse Collin | IRC: Larhzu @ IRCnet & Freenode
