symlink loop detected in path 'usr/share/doc/module-init-tools/changelog.Debian.gz'

(TBH I've no idea what debsums is nattering about, /usr/share/doc/module-init-tools/changelog.Debian.gz is a regular file, and no parent directory is a symlink.)

Status changed to 'Confirmed' because the bug affects multiple users.

strace -f debsums module-init-tools:

lstat("/usr/share/doc/module-init-tools", {st_mode=S_IFLNK|0777, st_size=23, ...}) = 0
readlink("/usr/share/doc/module-init-tools", "/usr/share/doc/libkmod2", 4095) = 23
write(2, "debsums: Error: symlink loop det"..., 146debsums: Error: symlink loop detected in path 'usr/share/doc/module-init-tools/changelog.Debian.gz'. Please file a bug against module-init-tools.

So it seems this is a bug in debsums, probably it assumes that there are no symlinked files in the relevant md5sums files.

/var/lib/dpkg/info/module-init-tools.md5sums file is just one line:

c629c0d493d1b6559648de3f63d398d9 usr/share/doc/module-init-tools/changelog.Debian.gz

But /usr/share/doc/module-init-tools is a symlink. And module-init-tools (24-1ubuntu3.2) itself is a pretty empty package, it just has that one file anyhow, and nothing depends on it, it can be removed. (It's only available in bionic anyway.)

It is debsums bug. Uninstalling module-init-tools lets debsums pass first error, but it throws same error on another package:

```
debsums: Error: symlink loop detected in path 'usr/share/doc/openoffice.org-calc/changelog.Debian.gz'. Please file a bug again openoffice.org-calc.
```

Not a problem with mentioned package, but with the tool "debsums"

I inspected perl code in /usr/bin/debsums...

The logic around catchink symlink loop is a bit flawed. Its in a function resolve_path() and it is only called from method .check() which intends to verify if the file can be opened. Since its goal is to find any bad files, symlink loop should be reported as any other file open errors, and the tool should not die, even if there is a legitimate symlink loop.

So I changed perl code - instead of 'die ...' -> 'return "";', and after 'my $resolved = resolve_path(...) added an if block:

         my $resolved = resolve_path($path,$pack);
+ if ($resolved eq "") {
+ warn "$self: symlink loop - can't open $pack file $root/$path ($@)\n";
+ return 2;
+ }

With that change debsums does not fail on the symlink loops and reports them with all other problem files.

BTW:
openoffice.org-calc package did not have symlink loop, but it linked to a file from uno-libs3 package, which did have a loop, reinstalling uno-libs3 package fixed/removed the loop.