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Gentoo Linux Security Advisory GLSA 200401-01 |
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~ http://security.gentoo.org |
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|
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~ Severity: High |
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~ Title: Linux kernel do_mremap() privilege escalation vulnerability |
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~ Date: January 08, 2004 |
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~ Bugs: #37292, #37317 |
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~ ID: 200401-01 |
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Synopsis |
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======== |
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|
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A critical security vulnerability has been found in recent Linux kernels |
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which allows for local privilege escalation. |
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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 memory management in a working |
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system - to allow this, processes are allowed to allocate and unallocate |
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memory. |
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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 Version / Manual Update? |
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~ ------------------------------------------------------------------- |
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|
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~ aa-sources................2.4.23-r1...................YES.......... |
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~ alpha-sources.............2.4.21-r2...................YES.......... |
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~ arm-sources...............2.4.19-r2................................ |
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~ ck-sources................2.4.23-r1...................YES.......... |
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~ compaq-sources............2.4.9.32.7-r1............................ |
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~ development-sources.......2.6.1_rc3................................ |
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~ gaming-sources............2.4.20-r7................................ |
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~ gentoo-dev-sources........2.6.1_rc3................................ |
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~ gentoo-sources............2.4.20-r10............................... |
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~ gentoo-sources............2.4.22-r3................................ |
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~ grsec-sources.............2.4.23.1.9.13-r1......................... |
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~ grsec-sources.............2.4.23.2.0_rc4-r1........................ |
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~ gs-sources................2.4.23_pre8-r2........................... |
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~ hardened-sources..........2.4.22-r2................................ |
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~ hppa-sources..............2.4.23_p4-r2........................... |
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~ ia64-sources..............2.4.22-r2................................ |
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~ mips-prepatch-sources.....2.4.24_pre2-r1........................... |
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~ mips-sources..............2.4.23-r2................................ |
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~ mm-sources................2.6.1_rc1-r2................YES.......... |
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~ openmosix-sources.........2.4.22-r3................................ |
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~ pac-sources...............2.4.23-r1................................ |
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~ pfeifer-sources...........2.4.21.1_pre4-r1......................... |
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~ planet-ccrma-sources......2.4.21-r4................................ |
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~ ppc-development-sources...2.6.1_rc1-r1................YES.......... |
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~ ppc-sources...............2.4.23-r1................................ |
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~ ppc-sources-benh..........2.4.22-r4................................ |
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~ ppc-sources-crypto........2.4.20-r2................................ |
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~ ppc-sources-dev...........2.4.22-r1................................ |
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~ selinux-sources...........2.4.24................................... |
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~ sparc-dev-sources.........2.6.1_rc2................................ |
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~ sparc-sources.............2.4.24................................... |
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~ usermode-sources..........2.4.23-r1................................ |
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~ vanilla-prepatch-sources..2.4.25_pre4.............................. |
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~ vanilla-sources...........2.4.24................................... |
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~ win4lin-sources...........2.6.0-r1................................. |
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~ wolk-sources..............4.9-r3................................... |
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~ wolk-sources..............4.10_pre7-r2............................. |
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~ xfs-sources...............2.4.23-r1................................ |
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|
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~ IMPORTANT: IF YOUR KERNEL IS MARKED AS "YES" ABOVE, THEN YOU SHOULD |
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~ UPDATE YOUR KERNEL EVEN IF PORTAGE REPORTS THAT THE SAME |
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~ VERSION IS INSTALLED. |
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|
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Description |
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=========== |
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|
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The memory subsystem allows for shrinking, growing, and moving of chunks |
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of memory along any of the allocated memory areas which the kernel |
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possesses. |
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|
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A typical virtual memory area covers at least one memory page. An |
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incorrect bound check discovered inside the do_mremap() kernel code |
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performing remapping of a virtual memory area may lead to creation of a |
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virtual memory area of 0 bytes length. |
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|
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The problem is based on the general mremap flaw that remapping 2 pages |
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from inside a VMA creates a memory hole of only one page in length but |
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an additional VMA of two pages. In the case of a zero sized remapping |
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request no VMA hole is created but an additional VMA descriptor of 0 |
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bytes in length is created. |
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This advisory also addresses an information leak in the Linux RTC system. |
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Impact |
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====== |
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|
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Arbitrary code may be able to exploit this vulnerability and may disrupt |
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the operation of other parts of the kernel memory management subroutines |
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finally leading to unexpected behavior. |
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|
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Since no special privileges are required to use the mremap() system call |
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any process may misuse its unexpected behavior to disrupt the kernel |
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memory management subsystem. Proper exploitation of this vulnerability |
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may lead to local privilege escalation including execution of arbitrary |
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code with kernel level access. |
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|
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Proof-of-concept exploit code [ 1 ] has been created and successfully |
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tested, permitting root escalation on vulnerable systems. As a result, |
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all users should upgrade their kernels to new or patched versions. |
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|
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Workaround |
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========== |
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There is no temporary workaround - a kernel upgrade is required. A list |
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of unaffected kernels is provided along with this announcement. |
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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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|
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~ $> # IMPORTANT: IF YOUR KERNEL IS MARKED AS "Manual Update" THEN |
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~ $> # THE PORTAGE MAY REPORT THAT YOU HAVE THE SAME KERNEL ON |
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~ $> # YOUR SYSTEM. YOU SHOULD STILL UPDATE YOUR KERNEL! |
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|
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~ $> emerge your-favorite-sources |
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|
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~ $> # Follow usual procedures 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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~ $> # See http://www.gentoo.org/doc/en/handbook/handbook.xml for help. |
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|
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References |
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========== |
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|
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~ [ 1 ] : http://isec.pl/vulnerabilities/isec-0012-mremap.txt |
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Concerns? |
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========= |
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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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