KSR[T] #009: Non Privileged Halt

From: Dave G. (dhgat_private)
Date: Fri Feb 05 1999 - 14:39:53 PST

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    KSR[T] Security Advisories
    http://www.ksrt.org
    ksrtat_private
    
    ---
    
                                                        KSR[T] Advisory #009
                                                        Date:  Feb. 5th 1999
                                                        ID #:  NonPrivdHALT
    
    Affected Program:    MILO/Alpha Linux
    
    Operating System(s): Linux (Redhat 5.x)
    
    Summary:             Any local user can cause an Alpha Linux machine to
                         reboot, lock up or become unstable.
    
    Problem Description: During the beta-testing of an instruction set
                         auditor, the KSR[T] team found several instructions
                         that caused an Alpha Linux machine to generate an
                         'Oops' or to reboot/hang.  This involves the call_pal
                         instruction with different immediate arguments.
    
                         The PALcode currently used in the MILO that comes
                         with Redhat 5.x and below has two additional
                         debugging PAL calls, DBGSTOP (0xAD) and NPHALT
                         (0xBF).  NPHALT is a non-privileged HALT
                         instruction, which brings the machine straight
                         back to the console even from user space.
    
                         These calls were used during the development of
                         MILO and were not intended for production use.
    
    Notes:               We would like to thank Richard Henderson,
                         Alan Cox for their help with this advisory.
    
                         Special thanks to Nikita Schmidt for the
                         problem description.
    
    Patch/Fix:           The copies of MILO distributed at
                         ftp://genie.ucd.ie/pub/alpha/milo/milo-latest
                         are not vulnerable to this attack.
    



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