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                         AUSCERT Security Bulletin

                               ASB-2009.1023
            Linux Kernel NULL Pointer Dereference Vulnerability
                               22 July 2009

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:              Linux kernel
Operating System:     Linux variants
Impact/Access:        Root Compromise     -- Existing Account
                      Denial of Service   -- Existing Account
                      Unauthorised Access -- Existing Account
                      Reduced Security    -- Existing Account
Resolution:           Patch
CVE Names:            CVE-2009-1897 CVE-2009-1895 
Member content until: Friday, August 21 2009

OVERVIEW

        A number of vulnerabilities in the Linux kernel before 2.6.30.2 have 
        been reported which could allow local security bypass, code 
        execution or a denial of service.


IMPACT

        (CVE-2009-1897)
        A NULL pointer dereference in the tun_chr_poll() function allows
        for a denial of service condition or the execution of arbitrary code 
        with root privileges if a local attacker were to open and poll a tun 
        device. [1]
        
        (CVE-2009-1895)
        A PER_CLEAR_ON_SETID mask in the the personality subsystem of the 
        Linux kernel does not include the ADDR_COMPAT_LAYOUT and MMAP_PAGE_ZERO 
        flags when executing a setuid or setgid program, allowing for memory 
        usage details to be procured. Local NULL pointer dereference attacks, 
        mmap_min_addr bypass and address space layout randomisation (ASLR)
        circumvention. [2]


MITIGATION

        A patch is available to download from the Linux Kernel Archives. [3]


REFERENCES

        [1] Linux Kernel tun_chr_poll() code execution
            http://xforce.iss.net/xforce/xfdb/51803

        [2] Linux 2.6.30.2 Changelog
            http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=3c8a9c63d5fd738c261bd0ceece04d9c8357ca13

        [3] The Linux Kernel Archives
            http://kernel.org/

AusCERT has made every effort to ensure that the information contained
in this document is accurate.  However, the decision to use the information
described is the responsibility of each user or organisation. The decision to
follow or act on information or advice contained in this security bulletin is
the responsibility of each user or organisation, and should be considered in
accordance with your organisation's site policies and procedures. AusCERT
takes no responsibility for consequences which may arise from following or
acting on information or advice contained in this security bulletin.

If you believe that your computer system has been compromised or attacked in 
any way, we encourage you to let us know by completing the secure National IT 
Incident Reporting Form at:

        http://www.auscert.org.au/render.html?it=3192

===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072

Internet Email: auscert@auscert.org.au
Facsimile:      (07) 3365 7031
Telephone:      (07) 3365 4417 (International: +61 7 3365 4417)
                AusCERT personnel answer during Queensland business hours 
                which are GMT+10:00 (AEST).
                On call after hours for member emergencies only.
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