You should get the original file somewhere and copy it there. and remove gainroot.old. Unfortunately I have the same situation so I don't know the original file.

You coulld just place empty file as gainroot too.

http://chris.intrepid.cx/N900/gainroot.old

Just scp'd from my phone

If you download it, remember to set it chmod 755

You can use it to replace /usr/sbin/gainroot (which appears to be the rootsh version! rootsh package needs some work

Before you copy it over, it might be worth pasting a copy of the file into a post here.. someone independent can verify I've not put something malicious in it

The md5 hash of the file can be verified using md5sum gainroot.old

8d30ec03fc1b8e6009b2e25c78fbc339

use md5sum gainroot.old to check your downloaded file matches this post

haven't tried but this should work :P

#!/bin/sh -e
trap exit SIGHUP SIGINT SIGTERM
PATH=/bin:/usr/bin:/sbin:/usr/sbin

if [ -x /mnt/initfs/usr/bin/cal-tool ]; then
CALTOOL="/usr/sbin/chroot /mnt/initfs cal-tool"
else
CALTOOL="cal-tool"
fi

MODE=`$CALTOOL --get-rd-mode`
if [ x$MODE = xenabled ]
then
echo "Root shell enabled"
/bin/sh
else
echo "Enable RD mode if you want to break your device"
fi

ok this worked last week perfectly and rootsh was uninstalled + root access disabled.

today i tried to reinstall rootsh, it installed but sudo gainroot is still asking for a password and just like last time the uninstaller through the app manager failed.

Did you figure out how to disable it? I got it to uninstall the same way you did but I still have root access...