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Re: slap_known_controls is unsafe (ITS#3291)

hyc@OpenLDAP.org wrote:

>Full_Name: Howard Chu
>Version: HEAD/2.2
>URL: ftp://ftp.openldap.org/incoming/
>Submission from: (NULL) (
>Submitted by: hyc
>back-ldap and back-meta initialize their bi->bi_controls (AKA be_controls) field
>using slap_known_controls during their backend initialization step. Also in HEAD
>the frontend does the same thing. Unfortunately this array is realloc'd when new
>controls are registered, which will invalidate the pointer that these
>backends/frontends are holding. Any subsequent reference to the bi_controls will
>likely result in a segfault.
>Since back-monitor examines this field during its startup, back-monitor will
>segfault if the controls array has changed between initialization and backend
>The controls array can be changed by modules loaded with moduleload in
>slapd.conf. For example, loading the ppolicy overlay will trigger this segfault.
>For back-ldap/back-meta we can probably move the initialization of bi_controls
>to a later point in the startup sequence.

Well, this was coded when controls could not be registered ddynamically;
 maybe all we need to do is turn slap_known_controls into a function;
moreover, the call that regsters new controls (as well as most of the calls
that register anything, which will likely be callable any time via protocol
and not just at startup) should be back-monitor aware, and call the 
hooks to add new entries/modify attribute values in existing entries.


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