Re: (ITS#7364) mdb: clean up POSIX semaphores on environment close.

[hyc@symas.com]

cmikk@qwest.net wrote:
> Full_Name: Chris Mikkelson
> Version: 2.4.32
> OS: FreeBSD
> URL: ftp://ftp.openldap.org/incoming/
> Submission from: (NULL) (204.147.85.37)
> 
> 
> When a back-mdb database is closed, the POSIX semaphores created when the mdb
> database was opened are left behind. This prevents a different user from opening
> the database.
> 
> For example, if you run slapd as an unprivileged user, stop slapd, and do an
> offline slapcat as root, slapd will not start up again as that unprivileged
> user. The only ways to recover I've found are:

This sounds like a bug in your platform's sem_open() syscall. If you first
started slapd as an unprivileged user, the semaphore should be owned by that
user. Running slapcat as root should not change the semaphore owner uid, and
the unprivileged owner should still be able to access the semaphore later.

Either that, or your description of the bug scenario is incomplete. I won't
commit your patch without a more complete understanding of the bug.

> a) reboot the machine
> b) restore the database from the slapcat, ensuring that slapadd runs as the
> correct user, or
> c) write a small program to re-generate the semaphore names an remove them.
> 
> The patch at:
> 
> http://mikk.net/~chris/patches/0002-Remove-POSIX-semaphores-when-the-last-user-closes-th.patch
> 
> Attempts to upgrade the lockfile lock to exclusive when closing the environment.
> If that upgrade succeeds, it removes the semaphores.
> 
> Patch has been tested on a BSD system. WIN32 has not been tested.

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