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==========================================================================
              AUSCERT External Security Bulletin Redistribution
                             
                      ESB-1999.135 -- FreeBSD-SA-99:02
                         Profiling Across Exec Calls
                              09 September 1999

===========================================================================

The FreeBSD Security Team has released the following advisory concerning
a vulnerability in the kernel's profiling implementation.  This
vulnerability may allow local users to gain root access.  No attacks using
this vulnerability are known at this time.

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=============================================================================
FreeBSD-SA-99:02                                            Security Advisory
                                                                FreeBSD, Inc.

Topic:          Profiling Across Exec Calls

Category:       core
Module:         kernel
Announced:      1999-09-04
Affects:        FreeBSD 3.2 (and earlier)
		FreeBSD-current before the correction date.
Corrected:      FreeBSD-3.3 RELEASE
		FreeBSD-current as of August 11, 1999
		FreeBSD-3.2-stable as of August 22, 1999
FreeBSD only:   No

Patches:        ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-99:02/

I.   Background

FreeBSD provides a mechanism to profile a running executable to aid in
performance tuning.  This can be accomplished via a kernel mechanism
to statistically sample the program counter of the program under
profile.

II.  Problem Description

A flaw exists in the implementation which allows an attacker to cause
arbitrary locations in program executed by the attacker.

III. Impact

No attacks against using this vulnerability this are known at this
time.  An attacker could theoretically gain root access from a
carefully crafted attack.

IV.  Workaround

Since profiling is done in the kernel via the profil(2) system call,
one must patch the kernel so no workaround is possible.

V.   Solution

Apply the following patch.  It will apply to both FreeBSD-current before
the resolution date and to 3.2-stable before the resolution date.

    Index: kern_exec.c
    ===================================================================
    RCS file: /home/imp/FreeBSD/CVS/src/sys/kern/kern_exec.c,v
    retrieving revision 1.99
    retrieving revision 1.100
    diff -u -r1.99 -r1.100
    --- kern_exec.c	1999/04/27 11:15:55	1.99
    +++ kern_exec.c	1999/08/11 20:35:38	1.100
    @@ -228,6 +228,9 @@
     		fdfree(p);
     		p->p_fd = tmp;
     	}
    +
    +	/* Stop profiling */
    +	stopprofclock(p);
     
     	/* close files on exec */
     	fdcloseexec(p);


=============================================================================
FreeBSD, Inc.

Web Site:                       http://www.freebsd.org/
Confidential contacts:          security-officer@freebsd.org
Security notifications:         security-notifications@freebsd.org
Security public discussion:     freebsd-security@freebsd.org
PGP Key:                ftp://ftp.freebsd.org/pub/FreeBSD/CERT/public_key.asc

Notice: Any patches in this document may not apply cleanly due to
        modifications caused by digital signature or mailer software.
        Please reference the URL listed at the top of this document
        for original copies of all patches if necessary.
=============================================================================

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