[UNIX] Linux Kernel do_mremap Local Privilege Escalation Vulnerability

From: SecuriTeam (support_at_securiteam.com)
Date: 01/05/04

  • Next message: SecuriTeam: "[EXPL] Webcam Watchdog Stack Overflow" 
    To: list@securiteam.com
Date: 5 Jan 2004 15:49:33 +0200

    The following security advisory is sent to the securiteam mailing list, and can be found at the SecuriTeam web site: http://www.securiteam.com
    - - promotion

    The SecuriTeam alerts list - Free, Accurate, Independent.

    Get your security news from a reliable source.
    http://www.securiteam.com/mailinglist.html

    - - - - - - - - -

      Linux Kernel do_mremap Local Privilege Escalation Vulnerability
    ------------------------------------------------------------------------

    SUMMARY

    A critical security vulnerability has been found in the Linux kernel
    memory management code in mremap(2) system call due to incorrect bound
    checks.

    DETAILS

    The mremap system call provides functionality of resizing (shrinking or
    growing) as well as moving across process's addressable space of existing
    virtual memory areas (VMAs) or any of its parts.

    A typical VMA covers at least one memory page (which is exactly 4kB on the
    i386 architecture). An incorrect bound check discovered inside the
    do_mremap() kernel code performing remapping of a virtual memory area may
    lead to creation of a virtual memory area of 0 bytes length.

    The problem bases on the general mremap flaw that remapping of 2 pages
    from inside a VMA creates a memory hole of only one page in length but an
    additional VMA of two pages. In the case of a zero sized remapping request
    no VMA hole is created but an additional VMA descriptor of 0 bytes in
    length is created.

    Such a malicious virtual memory area may disrupt the operation of other
    parts of the kernel memory management subroutines finally leading to
    unexpected behavior.

    A typical process's memory layout showing invalid VMA created with mremap
    system call:
        08048000-0804c000 r-xp 00000000 03:05 959142 /tmp/test
        0804c000-0804d000 rw-p 00003000 03:05 959142 /tmp/test
        0804d000-0804e000 rwxp 00000000 00:00 0
        40000000-40014000 r-xp 00000000 03:05 1544523 /lib/ld-2.3.2.so
        40014000-40015000 rw-p 00013000 03:05 1544523 /lib/ld-2.3.2.so
        40015000-40016000 rw-p 00000000 00:00 0
        4002c000-40158000 r-xp 00000000 03:05 1544529 /lib/libc.so.6
        40158000-4015d000 rw-p 0012b000 03:05 1544529 /lib/libc.so.6
        4015d000-4015f000 rw-p 00000000 00:00 0
    [*] 60000000-60000000 rwxp 00000000 00:00 0
        bfffe000-c0000000 rwxp fffff000 00:00 0

    The broken VMA in the above example has been marked with a [*].

    Impact:
    Since no special privileges are required to use the mremap(2) system call
    any process may misuse its unexpected behavior to disrupt the kernel
    memory management subsystem. Proper exploitation of this vulnerability may
    lead to local privilege escalation including execution of arbitrary code
    with kernel level access. Proof-of-concept exploit code has been created
    and successfully tested giving UID 0 shell on vulnerable systems.

    The exploitability of the discovered vulnerability is possible, although
    not a trivial one. Paul has identified at least two different attack
    vectors for the 2.4 kernel series. All users are encouraged to patch all
    vulnerable systems as soon as appropriate vendor patches are released.

    ADDITIONAL INFORMATION

    The original advisory is available at:
    <http://isec.pl/vulnerabilities/isec-0012-mremap.txt>
    http://isec.pl/vulnerabilities/isec-0012-mremap.txt.

    The information has been provided by <mailto:ihaquer@isec.pl> Paul
    Starzetz.

    ========================================

    This bulletin is sent to members of the SecuriTeam mailing list.
    To unsubscribe from the list, send mail with an empty subject line and body to: list-unsubscribe@securiteam.com
    In order to subscribe to the mailing list, simply forward this email to: list-subscribe@securiteam.com

    ====================
    ====================

    DISCLAIMER:
    The information in this bulletin is provided "AS IS" without warranty of any kind.
    In no event shall we be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages.

  • Next message: SecuriTeam: "[EXPL] Webcam Watchdog Stack Overflow"

    Relevant Pages