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Hash: SHA1 |
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Gentoo Linux Security Advisory GLSA 200403-02 |
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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 local privilege escalation |
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~ vulnerability |
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~ Date: March 06, 2004 |
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~ Bugs: #42024 |
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~ ID: 200403-02 |
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|
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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 |
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kernels by Paul Starzetz of iSEC Security Research which allows for |
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local privilege escalations. |
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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 |
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unallocate 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-r4................................ |
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~ ck-sources................2.4.24-r1...................YES.......... |
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~ ck-sources................2.6.2-r1....................YES.......... |
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~ compaq-sources............2.4.9.32.7-r2............................ |
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~ development-sources.......2.6.3_rc1................................ |
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~ gaming-sources............2.4.20-r8................................ |
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~ gentoo-dev-sources........2.6.3_rc1................................ |
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~ gentoo-sources............2.4.19-r11............................... |
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~ gentoo-sources............2.4.20-r12............................... |
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~ gentoo-sources............2.4.22-r7................................ |
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~ grsec-sources.............2.4.24.1.9.13-r1......................... |
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~ gs-sources................2.4.25_pre7-r2........................... |
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~ hardened-sources..........2.4.24-r1................................ |
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~ hppa-dev-sources..........2.6.2_p3-r1.............................. |
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~ hppa-sources..............2.4.24_p0-r1............................. |
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~ ia64-sources..............2.4.24-r1................................ |
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~ mips-prepatch-sources.....2.4.25_pre6-r1........................... |
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~ mips-sources..............2.4.25_rc4............................... |
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~ mm-sources................2.6.3_rc1-r1............................. |
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~ openmosix-sources.........2.4.22-r4................................ |
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~ pac-sources...............2.4.23-r3................................ |
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~ planet-ccrma-sources......2.4.21-r5................................ |
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~ ppc-development-sources...2.6.3_rc1-r1............................. |
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~ ppc-sources...............2.4.24-r1................................ |
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~ ppc-sources-benh..........2.4.22-r5................................ |
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~ ppc-sources-crypto........2.4.20-r3................................ |
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~ ppc-sources-dev...........2.4.24-r2................................ |
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~ selinux-sources...........2.4.24-r2................................ |
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~ sparc-dev-sources.........2.6.3_rc1................................ |
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~ sparc-sources.............2.4.24-r2................................ |
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~ usermode-sources..........2.4.24-r1................................ |
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~ usermode-sources..........2.6.3-r1................................. |
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~ vanilla-prepatch-sources..2.4.25_rc4............................... |
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~ vanilla-sources...........2.4.25................................... |
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~ win4lin-sources...........2.4.23-r2................................ |
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~ win4lin-sources...........2.6.2-r1................................. |
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~ wolk-sources..............4.9-r4................................... |
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~ wolk-sources..............4.10_pre7-r3............................. |
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~ xfs-sources...............2.4.24-r2................................ |
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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 |
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chunks of memory along any of the allocated memory areas which the |
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kernel posesses. |
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|
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To accomplish this, the do_mremap code calls the do_munmap() kernel |
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function to remove any old memory mappings in the new location - but, |
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the code doesn't check the return value of the do_munmap() function |
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which may fail if the maximum number of available virtual memory area |
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descriptors has been exceeded. |
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|
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Due to the missing return value check after trying to unmap the middle |
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of the first memory area, the corresponding page table entries from |
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the second new area are inserted into the page table locations |
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described by the first old one, thus they are subject to page |
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protection flags of the first area. As a result, arbitrary code can be |
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executed. |
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|
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Impact |
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====== |
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|
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Arbitrary code with normal non-superuser privelerges may be able to |
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exploit this vulnerability and may disrupt the operation of other |
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parts of the kernel memory management subroutines finally leading to |
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unexpected behavior. |
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|
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Since no special privileges are required to use the mremap() and |
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mummap() system calls any process may misuse this unexpected behavior |
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to disrupt the kernel memory management subsystem. Proper exploitation |
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of this vulnerability may lead to local privilege escalation allowing |
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for the execution of arbitrary code with kernel level root access. |
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|
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Proof-of-concept exploit code 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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|
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Users who are unable to upgrade their kernels may attempt to use "sysctl |
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- -w vm.max_map_count=1000000", however, this is a temporary fix which |
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only solves the problem by increasing the number of memory areas that |
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can be created by each process. Because of the static nature of this |
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workaround, it is not recommended and users are urged to upgrade their |
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systems to the latest avaiable patched sources. |
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|
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Resolution |
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========== |
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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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|
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~ # emerge sync |
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~ # emerge -pv your-favourite-sources |
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~ # emerge your-favourite-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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~ # # IF YOUR KERNEL IS MARKED as "remerge required!" THEN |
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~ # # YOU SHOULD UPDATE YOUR KERNEL EVEN IF PORTAGE |
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~ # # REPORTS THAT THE SAME VERSION IS INSTALLED. |
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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-0014-mremap-unmap.txt |
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|
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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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|
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