bin/115631: make dlclose atexit-aware (patch)

[Mikhail T.]

>Number:         115631
>Category:       bin
>Synopsis:       make dlclose atexit-aware (patch)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          change-request
>Submitter-Id:   current-users
>Arrival-Date:   Sun Aug 19 21:00:03 GMT 2007
>Closed-Date:
>Last-Modified:
>Originator:     Mikhail T.
>Release:        FreeBSD 6.2-STABLE amd64
>Organization:
Virtual Estates, Inc.
>Environment:
System: FreeBSD 6.2-STABLE

>Description:
	Currently, an application can shoot itself in the tail by
	registering a symbol with atexit and then dlclose-ing the
	library, which provides the symbol.

	Programs aren't supposed to that, but sometimes they do --
	most notably ImageMagick, which dlopens libjasper, which
	registers its own clean-up routine with atexit.

	The proposed patch will make such bugs easier to diagnose --
	the ImageMagick problem (crash upon exiting) was mystifying
	people for years...

>How-To-Repeat:

>Fix:
	The up-to-date version of the patch can be found here:

		http://aldan.algebra.com/~mi/dlclose-atexit.patch

	It exposes the __atexit pointer defined in atexit.c and its
	type and modifies dlclose to scan through all listed functions
	looking for those, that belong to the object being dlclosed.

	The method to check whether a symbol belongs to an object
	is to check, whether the address is between mapbase and
	mapbase+mapsize of the entry.

	What could be improved is the addition of a an addr_to_name
	lookup -- to print the _name_ of the function found to be
	registered with atexit, rather than merely the function's
	address.
>Release-Note:
>Audit-Trail:
>Unformatted: