MySQL Bugs: #2631: mlockall called after dropping root permissions

Bug #2631	mlockall called after dropping root permissions
Submitted:	3 Feb 2004 10:55	Modified:	7 Sep 2004 8:28
Reporter:	[ name withheld ]	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server	Severity:	S3 (Non-critical)
Version:	4.0	OS:
Assigned to:	Ramil Kalimullin	CPU Architecture:	Any

Description:
The memlock option does not work if --user is also used to run the daemon as non-root.  The call to mlockall needs to be made before doing setuid to become non-root, else it fails for lack of permissions.

This bug was filed in Red Hat's bugzilla and I'm just passing it upstream:
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=81378
AFAICS the issue is still present in MySQL 4.0.17, but the patch proposed by the original submitter no longer applies.

How to repeat:
See above link for details.

Verified, and additionally as written it would appear that mlockall() is not even called unless running as root, yet locked_in_memory remains true.

Fx on dev-bugs
Subj: Fix for bug2631: mlockall called after dropping root permissions
Date: 2004-03-19

The problem is becasue of how the database layer is designed we can only use mlockall if you are running the mysqld server as root.

The reason is that we must call mlockall() after all databases has been initialized and have allocated their memory. We can't however call set_user() after the databases has been initialized becasue then the databases & log files would be owned by the wrong user.

The MySQL documentation already states that to use this the --memlock option you must run the MySQL server as root.

another solution is being considered

Sergei, please review my fix:
ChangeSet
  1.2008 04/09/03 19:26:11 ram@gw.mysql.r18.ru

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