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CVS: cvs.openbsd.org: src

Module name:	src
Changes by:	djm_(_at_)_cvs_(_dot_)_openbsd_(_dot_)_org	2008/12/29 15:25:50

Modified files:
	lib/libc/stdlib: malloc.3 malloc.c 

Log message:
extra paranoia for malloc(3):

Move all runtime options into a structure that is made read-only
(via mprotect) after initialisation to protect against attacks that
overwrite options to turn off malloc protections (e.g. use-after-free)

Allocate the main bookkeeping data (struct dir_info) using mmap(),
thereby giving it an unpredictable address. Place a PROT_NONE guard
page on either side to further frustrate attacks on it.

Add a new 'L' option that maps struct dir_info PROT_NONE except when
in the allocator code itself. Makes attacks on it basically impossible.

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