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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2007.0393 -- [Linux] Linux Kernel cpuset tasks Information Disclosure Vulnerability 11 June 2007 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Linux Kernel Publisher: iDefense Operating System: Linux variants Impact: Access Privileged Data Access: Existing Account CVE Names: CVE-2007-2875 Original Bulletin: http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=541 - --------------------------BEGIN INCLUDED TEXT-------------------- Linux Kernel cpuset tasks Information Disclosure Vulnerability iDefense Security Advisory 06.07.07 http://labs.idefense.com/intelligence/vulnerabilities/ Jun 07, 2007 I. BACKGROUND Linux is a clone of the UNIX operating system, written from scratch by Linus Torvalds with assistance from a loosely-knit team of hackers across the Internet. The cpuset functionality allows process to be assigned to processors on multi-processor machines. II. DESCRIPTION Local exploitation of an information disclosure vulnerability within the Linux Kernel allows attackers to obtain sensitive information from kernel memory. This vulnerability specifically exists in the "cpuset_tasks_read" function. This function is responsible for supplying user-land processes with data when they read from the /dev/cpuset/tasks file. The code excerpt below shows the problem area. 1754 if (*ppos + nbytes > ctr->bufsz) 1755 nbytes = ctr->bufsz - *ppos; 1756 if (copy_to_user(buf, ctr->buf + *ppos, nbytes)) By reading from an offset (*ppos) larger than the contents of the file, an attacker can cause an integer underflow to occur in the subtraction on line 1755. This will result in the "copy_to_user" function on line 1756 to be called with a memory address located at a lower address than the start of the intended buffer. This memory could potentially contain sensitive information such as security tokens or passwords. III. ANALYSIS Exploitation of this vulnerability allows attackers to obtain sensitive information from kernel memory. In order to exploit this vulnerability, an attacker would need access to open the /dev/cpuset/tasks file. It is important to note that this file does not exist unless the cpuset file system has been mounted. Additionally, this functionality is not included by default in a vanilla kernel build. Furthermore, because of checks at the VFS layer and in the 'copy_to_user()' function, an attacker cannot use arbitrary values. However, on 32-bit systems it is easily exploitable. IV. DETECTION iDefense has confirmed the existence of this vulnerability in version 2.6.20 of the Linux Kernel as installed with Fedora CORE 6. It is suspected that previous versions, at least until 2.6.12, are also vulnerable. V. WORKAROUND In order to prevent exploitation of this vulnerability, discontinue use of the cpuset file system. This can be accomplished by un-mounting the file system using the "umount" command. VI. VENDOR RESPONSE The Linux kernel team has released versions 2.6.20.13 and 2.6.21.4 to address this vulnerability. More information can be found via the following URLs. http://kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.20.13 http://kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.21.4 VII. CVE INFORMATION The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2007-2875 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org/), which standardizes names for security problems. VIII. DISCLOSURE TIMELINE 04/27/2007 Initial vendor notification 06/04/2007 Second vendor notification 06/04/2007 Initial vendor response 06/07/2007 Coordinated public disclosure IX. CREDIT The discoverer of this vulnerability wishes to remain anonymous. Get paid for vulnerability research http://labs.idefense.com/methodology/vulnerability/vcp.php Free tools, research and upcoming events http://labs.idefense.com/ X. LEGAL NOTICES Copyright © 2007 iDefense, Inc. Permission is granted for the redistribution of this alert electronically. It may not be edited in any way without the express written consent of iDefense. If you wish to reprint the whole or any part of this alert in any other medium other than electronically, please e-mail customerservice@idefense.com for permission. Disclaimer: The information in the advisory is believed to be accurate at the time of publishing based on currently available information. Use of the information constitutes acceptance for use in an AS IS condition. There are no warranties with regard to this information. Neither the author nor the publisher accepts any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information. - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. 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. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/render.html?cid=1980 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. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQCVAwUBRmypdCh9+71yA2DNAQIm5QP/bBUdva/cftIsbYb5a8RYEzE0uYACpPv7 JlFWgcAMJxbqtaS5su8ppkrU0NbFhH8PEyiN2t1gDtvb3DuCqm2hDmWz8KVZ1JfN KuOtkqnp/VB+PQlvWI90n4qxX3asBgrJgaoia1Hr/JwbbENBoDdCSE4mq9XS1cAb eGK2eTmQvsU= =ZZWm -----END PGP SIGNATURE-----