There are many reasons for these types of defects. The programmer(s) in
these cases to the best of my knowledge were actually very experienced
z/OS developers. Very competent people. In my experience it is a matter
of when not if these type of issues occur when you are responsible for
developing and maintaining this type of code. It requires a constant
vigilance to make sure these types of errors don't get out into the
field. Even then it only takes a single "error" that could compromise
the system integrity. It is a difficult job.
Ray Overby
Key Resources, Inc.
Ensuring System Integrity for z/Series^(TM)
www.zassure.com
(312)574-0007
On 3/27/2012 19:30 PM, Gerhard Postpischil wrote:
On 3/27/2012 7:27 PM, Ray Overby wrote:
Like any SVC when invoked it will get control in an authorized
state (PSW Key 0). Further this SVC issues a STM instruction
very early in the SVC code storing into where ever R13 points
to. This type of defect is easily exploited writing a simple
program (could have been posted on the web) that would issue the
SVC and:
Defect is the correct description; your SVC sounds as though written
by an incompetent programmer. User's registers are preserved in the RB
(PRB, SVRB), where they are protected, rather than the save area.
Off-hand I can't recall any SVC that needs R13 to point to a save
area, rather there are cases where R13 is destroyed.
Gerhard Postpischil
Bradford, VT
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