Adduser devel - Mar 2006 - Bug#355708: adduser: symlinks in /etc/skel sometimes break adduser

Package: adduser
Version: 3.80
Severity: normal
Tags: patch

The presence of symlinks in /etc/skel sometimes breaks adduser as
follows:

  Adding user `test''...
  Adding new group `test'' (1000).
  Adding new user `test'' (1000) with group `test''.
  Creating home directory `/home/test''.
  Copying files from `/etc/skel''
  symlink: Bad file descriptor
  Cleaning up.
  Removing directory `/home/test''
  Removing user `test''.
  Removing group `test''.
  groupdel: group test does not exist
  adduser: `groupdel test` returned error code 6.  Aborting.

Unfortunately the only environment in which I''ve been able to reproduce
this reliably is in the Ubuntu live CD installer, which isn''t something
I can expect you to be able to randomly test. :-( I don''t know why it
shows up in this environment but not in others. However, on looking at
the code, the cause is clear: copy_to_dir() looks at $! after calling
symlink() without checking symlink()''s return code first, and in the
event that symlink() succeeds $! is essentially random.

Here''s a patch (against 3.80 since that''s what we have in
Ubuntu, but
the surrounding code doesn''t seem to have changed between that and
3.85). Changelog entry: "Only check $! after calling symlink() if
symlink() fails.":

diff -Nru /tmp/WwKkNgpSc2/adduser-3.80/adduser
/tmp/eVp2gJwz5F/adduser-3.80ubuntu1/adduser
--- /tmp/WwKkNgpSc2/adduser-3.80/adduser	2005-11-18 17:15:59.000000000 +0000
+++ /tmp/eVp2gJwz5F/adduser-3.80ubuntu1/adduser	2006-03-07 11:38:39.000000000
+0000
@@ -680,8 +680,7 @@
 	my $error="";
 	$)="$newg";
 	$>="$newu";
-	symlink("$target", "$todir/$file");
-	$error="$!";
+	symlink("$target", "$todir/$file") or
$error="$!";
         $>="$curuid";
         $)="$curgid";
 	if( "$error" ne "" ) {

Thanks,

-- 
Colin Watson                                       [cjwatson@debian.org]

Processing commands for control@bugs.debian.org:
> tags #355708 confirmed pending
Bug#355708: adduser: symlinks in /etc/skel sometimes break adduser
Tags were: patch
Tags added: confirmed, pending
> thanks
Stopping processing here.

Please contact me if you need assistance.

Debian bug tracking system administrator
(administrator, Debian Bugs database)

tags #355708 confirmed pending
thanks

On Tue, Mar 07, 2006 at 02:26:31PM +0000, Colin Watson
wrote:
> Here''s a patch (against 3.80 since that''s what we have in
Ubuntu, but
> the surrounding code doesn''t seem to have changed between that and
> 3.85). Changelog entry: "Only check $! after calling symlink() if
> symlink() fails.":
Applied in svn, thanks.

Greetings
Marc

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Your message dated Sat, 15 Apr 2006 13:47:13 -0700
with message-id <E1FUrfl-0001Gf-1N@spohr.debian.org>
and subject line Bug#355708: fixed in adduser 3.86
has caused the attached Bug report to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.

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Debian bug tracking system administrator
(administrator, Debian Bugs database)

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