NetBSD Problem Report #46872

From  Wed Aug 29 14:31:10 2012
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Date: Wed, 29 Aug 2012 16:30:55 +0200 (CEST)
Subject: mtrr_i686.c may access uninitialized data
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>Number:         46872
>Category:       kern
>Synopsis:       mtrr_i686.c may access uninitialized data
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Aug 29 14:35:00 +0000 2012
>Originator:     Wolfgang Stukenbrock
>Release:        NetBSD 5_1_STABLE - current is affected too
Dr. Nagler & Company GmbH

System: NetBSD test-s0 4.0 NetBSD 4.0 (NSW-WS) #0: Tue Aug 17 17:28:09 CEST 2010 wgstuken@test-s0:/usr/src/sys/arch/amd64/compile/NSW-WS amd64
Architecture: x86_64
Machine: amd64
	The kernel uses a static allocated array "mttr_raw[]" that is initialized with some default values.
	In i686_mtrr_init_first() the message is printed if the actual CPU has more MTRR's as supported.
	In i686_raw2soft() there is a loop with the actual number of MTRR's that accesses an allocated array
	of the correct size, but it also accesses "mttr_raw[]" via the pointer "mtrr_var_raw" that is initialized
	with "mtrr_var_raw = &mtrr_raw[0];"
	If there are more MTRR's as supported, the "other" entries in "mttr_raw[]" are accesed or if there are much
	more MTRR's, we access memory behind the array.
	I've not looked if there are even more places where this happens.
	I've a crash during boot and saw the messages that there are too much MTRR's for the kernel.
	Then I've looked into the sources. I do not know if this is related or not, but it is a bug in any case.
	Not known, because I do not know much about the MTRR's - sorry.
	If possible, eliminate the static array and do a complete dynamic initialisation. A comment in mttr.h assumes,
	that there may be up to 255 MTRR's on a CPU.


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