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Gentoo Linux Security Advisory GLSA 200407-16 |
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http://security.gentoo.org/ |
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Severity: High |
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Title: Linux Kernel: Multiple DoS and permission vulnerabilities |
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Date: July 22, 2004 |
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Bugs: #56171, #56479 |
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ID: 200407-16 |
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Synopsis |
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======== |
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|
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Multiple permission vulnerabilities have been found in the Linux |
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kernel, allowing an attacker to change the group IDs of files mounted |
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on a remote filesystem (CAN-2004-0497), as well as an issue in 2.6 |
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series kernels which allows /proc permissions to be bypassed. |
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|
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A context sharing vulnerability in vserver-sources is also handled by |
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this advisory as well as CAN-2004-0447, CAN-2004-0496 and |
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CAN-2004-0565. Patched, or updated versions of these kernels have been |
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released and details are included along with this advisory. |
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|
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Background |
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========== |
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|
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The Linux kernel is responsible for managing the core aspects of a |
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GNU/Linux system, providing an interface for core system applications |
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as well as providing the essential structure and capability to access |
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hardware that is needed for a running system. |
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|
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Affected packages |
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================= |
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|
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------------------------------------------------------------------- |
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Kernel / Unaffected / Remerge |
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------------------------------------------------------------------- |
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1 aa-sources ................. *>= 2.4.23-r2 .................. YES |
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............................. >= 2.6.5-r5 ................... YES |
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2 alpha-sources .............. >= 2.4.21-r9 ....................... |
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3 ck-sources ................. *>= 2.4.26-r1 .................. YES |
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............................. >= 2.6.7-r5 ................... YES |
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4 compaq-sources ........... >= 2.4.9.32.7-r8 ..................... |
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5 development-sources ........ >= 2.6.8_rc1 ....................... |
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6 gentoo-dev-sources .......... >= 2.6.7-r8 ....................... |
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7 gentoo-sources ............ *>= 2.4.19-r18 ...................... |
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........................... *>= 2.4.20-r21 ...................... |
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........................... *>= 2.4.22-r13 ...................... |
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............................ *>= 2.4.25-r6 ...................... |
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............................ >= 2.4.26-r5 ....................... |
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8 grsec-sources ............ >= 2.4.26.2.0-r6 ..................... |
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9 gs-sources ............... >= 2.4.25_pre7-r8 .................... |
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10 hardened-dev-sources ........ >= 2.6.7-r2 ....................... |
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11 hardened-sources ........... >= 2.4.26-r3 ....................... |
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12 hppa-dev-sources .......... >= 2.6.7_p1-r2 ...................... |
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13 hppa-sources .............. >= 2.4.26_p6-r1 ..................... |
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14 ia64-sources ............... >= 2.4.24-r7 ....................... |
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15 mm-sources .................. >= 2.6.7-r6 ....................... |
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16 openmosix-sources .......... >= 2.4.22-r11 ...................... |
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17 pac-sources ................ >= 2.4.23-r9 ....................... |
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18 planet-ccrma-sources ....... >= 2.4.21-r11 ...................... |
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19 pegasos-dev-sources ......... >= 2.6.7-r2 ....................... |
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20 pegasos-sources ............ >= 2.4.26-r3 ....................... |
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21 ppc-sources ................ >= 2.4.26-r3 ....................... |
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22 rsbac-sources .............. >= 2.4.26-r3 ....................... |
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23 rsbac-dev-sources ........... >= 2.6.7-r2 ....................... |
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24 selinux-sources ............ >= 2.4.26-r2 ................... YES |
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25 sparc-sources .............. >= 2.4.26-r3 ....................... |
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26 uclinux-sources .......... *>= 2.4.26_p0-r3 ..................... |
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........................... >= 2.6.7_p0-r2 ...................... |
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27 usermode-sources ........... *>= 2.4.24-r6 ...................... |
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............................ *>= 2.4.26-r3 ...................... |
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............................. >= 2.6.6-r4 ....................... |
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28 vserver-sources .......... >= 2.4.26.1.28-r1 .................... |
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29 win4lin-sources ............ *>= 2.4.26-r3 ...................... |
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............................. >= 2.6.7-r2 ....................... |
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30 wolk-sources ................ *>= 4.9-r10 ....................... |
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............................. *>= 4.11-r7 ....................... |
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............................. >= 4.14-r4 ........................ |
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31 xbox-sources ............... *>= 2.4.26-r3 ...................... |
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............................. >= 2.6.7-r2 ....................... |
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32 mips-sources ................ Vulnerable! ....................... |
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33 vanilla-sources ............. Vulnerable! ....................... |
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------------------------------------------------------------------- |
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NOTE: Some kernels are still vulnerable. Users should migrate to |
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another kernel if one is available or seek another |
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solution such as patching their existing kernel. |
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------------------------------------------------------------------- |
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NOTE: Packages marked with "Remerge" as "YES" require a re-merge |
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even though Portage does not indicate a newer version! |
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------------------------------------------------------------------- |
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33 affected packages on all of their supported architectures. |
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------------------------------------------------------------------- |
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|
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Description |
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=========== |
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|
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The Linux kernel allows a local attacker to mount a remote file system |
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on a vulnerable Linux host and modify files' group IDs. On 2.4 series |
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kernels this vulnerability only affects shared NFS file systems. This |
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vulnerability has been assigned CAN-2004-0497 by the Common |
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Vulnerabilities and Exposures project. |
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|
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Also, a flaw in the handling of /proc attributes has been found in 2.6 |
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series kernels; allowing the unauthorized modification of /proc |
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entries, especially those which rely solely on file permissions for |
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security to vital kernel parameters. |
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|
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An issue specific to the VServer Linux sources has been found, by which |
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/proc related changes in one virtual context are applied to other |
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contexts as well, including the host system. |
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|
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CAN-2004-0447 resolves a local DoS vulnerability on IA64 platforms |
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which can cause unknown behavior and CAN-2004-0565 resolves a floating |
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point information leak on IA64 platforms by which registers of other |
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processes can be read by a local user. |
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Finally, CAN-2004-0496 addresses some more unknown vulnerabilities in |
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2.6 series Linux kernels older than 2.6.7 which were found by the |
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Sparse source code checking tool. |
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|
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Impact |
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====== |
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|
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Bad Group IDs can possibly cause a Denial of Service on parts of a host |
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if the changed files normally require a special GID to properly |
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operate. By exploiting this vulnerability, users in the original file |
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group would also be blocked from accessing the changed files. |
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|
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The /proc attribute vulnerability allows local users with previously no |
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permissions to certain /proc entries to exploit the vulnerability and |
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then gain read, write and execute access to entries. |
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These new privileges can be used to cause unknown behaviour ranging |
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from reduced system performance to a Denial of Service by manipulating |
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various kernel options which are usually reserved for the superuser. |
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This flaw might also be used for opening restrictions set through /proc |
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entries, allowing further attacks to take place through another |
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possibly unexpected attack vector. |
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|
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The VServer issue can also be used to induce similar unexpected |
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behaviour to other VServer contexts, including the host. By successful |
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exploitation, a Denial of Service for other contexts can be caused |
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allowing only root to read certain /proc entries. Such a change would |
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also be replicated to other contexts, forbidding normal users on those |
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contexts to read /proc entries which could contain details needed by |
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daemons running as a non-root user, for example. |
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|
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Additionally, this vulnerability allows an attacker to read information |
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from another context, possibly hosting a different server, gaining |
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critical information such as what processes are running. This may be |
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used for furthering the exploitation of either context. |
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CAN-2004-0447 and CAN-2004-0496 permit various local unknown Denial of |
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Service vulnerabilities with unknown impacts - these vulnerabilities |
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can be used to possibly elevate privileges or access reserved kernel |
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memory which can be used for further exploitation of the system. |
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|
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CAN-2004-0565 allows FPU register values of other processes to be read |
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by a local user setting the MFH bit during a floating point operation - |
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since no check was in place to ensure that the FPH bit was owned by the |
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requesting process, but only an MFH bit check, an attacker can simply |
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set the MFH bit and access FPU registers of processes running as other |
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users, possibly those running as root. |
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Workaround |
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========== |
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2.4 users may not be affected by CAN-2004-0497 if they do not use |
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remote network filesystems and do not have support for any such |
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filesystems in their kernel configuration. All 2.6 users are affected by |
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the /proc attribute issue and the only known workaround is to disable |
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/proc support. |
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The VServer flaw applies only to vserver-sources, and no workaround is |
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currently known for the issue. There is no known fix to CAN-2004-0447, |
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CAN-2004-0496 or CAN-2004-0565 other than to upgrade the kernel to a |
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patched version. |
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As a result, all users affected by any of these vulnerabilities should |
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upgrade their kernels to ensure the integrity of their systems. |
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Resolution |
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========== |
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Users are encouraged to upgrade to the latest available sources for |
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their system: |
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# emerge sync |
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# emerge -pv your-favorite-sources |
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# emerge your-favorite-sources |
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# # Follow usual procedure for compiling and installing a kernel. |
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# # If you use genkernel, run genkernel as you would do normally. |
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|
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References |
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========== |
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|
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[ 1 ] CAN-2004-0447 |
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http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0447 |
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[ 2 ] CAN-2004-0496 |
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http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0496 |
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[ 3 ] CAN-2004-0497 |
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http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0497 |
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[ 4 ] CAN-2004-0565 |
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http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0565 |
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[ 5 ] VServer /proc Context Vulnerability |
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http://www.securityfocus.com/archive/1/367977 |
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|
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Availability |
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============ |
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|
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This GLSA and any updates to it are available for viewing at |
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the Gentoo Security Website: |
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|
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http://security.gentoo.org/glsa/glsa-200407-16.xml |
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Concerns? |
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========= |
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Security is a primary focus of Gentoo Linux and ensuring the |
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confidentiality and security of our users machines is of utmost |
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importance to us. Any security concerns should be addressed to |
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security@g.o or alternatively, you may file a bug at |
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http://bugs.gentoo.org. |
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|
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License |
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======= |
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|
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Copyright 2004 Gentoo Foundation, Inc; referenced text |
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belongs to its owner(s). |
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|
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The contents of this document are licensed under the |
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Creative Commons - Attribution / Share Alike license. |
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|
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http://creativecommons.org/licenses/by-sa/1.0 |
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