Bug 172775

Description of problem:
I'm using replication and the MySQL servers are occasionally caching the wrong
values for hostnames (see URL). It appears that all the users who reported the
bug to MySQL are Red Hat users.

Version-Release number of selected component (if applicable):
mysql-server-4.1.14-1.FC4.1

How reproducible:
sometimes

Steps to Reproduce:
1.Set up replication
2.access master from many hosts (sorry this is vague)
3.watch for inconsistencies: make a connection from foo.example.com and do
SELECT USER();
  
Actual results:
notice that it says user.com

Expected results:
user.com

Additional info:

Problem goes away when we disable the MySQL host cache.

$ grep hosts /etc/nsswitch.conf
hosts:   dns nis [NOTFOUND=return] files

Nothing freaky in /etc/hosts

$ ypcat hosts
127.0.0.1       localhost loghost
129.234.4.13    timehost
129.234.4.78    nsrhost
127.0.0.1       localhost loghost

The DNS entries don't change (!)

getent hosts foo.example.com and its IP works fine.

Running NSCD but I've had this problem with NSCD turned off too.

ObSecurity:
I assert that this is a possible security problem because many sites use
host-based MySQL access control rules. It certainly caused me a denial of
service when the replication master had the wrong value for the replication slave.