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  • [FreeBSD-Announce] FreeBSD Security Advisory FreeBSD-SA-21:04.jail_remo

    From FreeBSD Security Advisories@21:1/5 to All on Wed Feb 24 07:00:03 2021
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    ============================================================================= FreeBSD-SA-21:04.jail_remove Security Advisory
    The FreeBSD Project

    Topic: jail_remove(2) fails to kill all jailed processes

    Category: core
    Module: jail
    Announced: 2021-02-24
    Credits: Mateusz Guzik
    Affects: All supported versions of FreeBSD.
    Corrected: 2021-02-19 01:22:08 UTC (stable/13, 13.0-STABLE)
    2021-02-19 21:53:07 UTC (releng/13.0, 13.0-BETA3-p1)
    2021-02-19 21:46:31 UTC (stable/12, 12.2-STABLE)
    2021-02-24 01:43:39 UTC (releng/12.2, 12.2-RELEASE-p4)
    2021-02-19 21:50:26 UTC (stable/11, 11.4-STABLE)
    2021-02-24 01:41:41 UTC (releng/11.4, 11.4-RELEASE-p8)
    CVE Name: CVE-2020-25581

    For general information regarding FreeBSD Security Advisories,
    including descriptions of the fields above, security branches, and the following sections, please visit <URL:https://security.FreeBSD.org/>.

    I. Background

    The jail(2) system call allows a system administrator to lock a process
    and all of its descendants inside an environment with a very limited
    ability to affect the system outside that environment, even for
    processes with superuser privileges. It is an extension of, but
    far more powerful than, the traditional UNIX chroot(2) system call.

    The jail_remove(2) system call, which was introduced in FreeBSD 8.0,
    allows a non-jailed process to remove a jail, which includes terminating
    all the processes running in that jail.

    II. Problem Description

    Due to a race condition in the jail_remove(2) implementation, it may fail
    to kill some of the processes.

    III. Impact

    A process running inside a jail can avoid being killed during jail termination. If a jail is subsequently started with the same root path, a lingering jailed process may be able to exploit the window during which a devfs filesystem is mounted but the jail's devfs ruleset has not been applied, to access device nodes which are ordinarily inaccessible. If the process is privileged, it may be able to escape the jail and gain full access to the system.

    IV. Workaround

    The problem is limited to scenarios where a jail containing an untrusted, privileged process is stopped, and a jail is subsequently started with the same root path. Users not running jails are not affected, and the problem can be avoided by not starting a jail with the same path as a previously stopped jail.

    V. Solution

    Upgrade your vulnerable system to a supported FreeBSD stable or
    release / security branch (releng) dated after the correction date and reboot.

    Perform one of the following:

    1) To update your vulnerable system via a binary patch:

    Systems running a RELEASE version of FreeBSD on the i386 or amd64
    platforms can be updated via the freebsd-update(8) utility:

    # freebsd-update fetch
    # freebsd-update install
    # shutdown -r +10min "Rebooting for a security update"

    2) To update your vulnerable system via a source code patch:

    The following patches have been verified to apply to the applicable
    FreeBSD release branches.

    a) Download the relevant patch from the location below, and verify the
    detached PGP signature using your PGP utility.

    [FreeBSD 13.x]
    # fetch https://security.FreeBSD.org/patches/SA-21:04/jail_remove.13.patch
    # fetch https://security.FreeBSD.org/patches/SA-21:04/jail_remove.13.patch.asc # gpg --verify jail_remove.13.patch.asc

    [FreeBSD 11.x, FreeBSD 12.x]
    # fetch https://security.FreeBSD.org/patches/SA-21:04/jail_remove.patch
    # fetch https://security.FreeBSD.org/patches/SA-21:04/jail_remove.patch.asc
    # gpg --verify jail_remove.patch.asc

    b) Apply the patch. Execute the following commands as root:

    # cd /usr/src
    # patch < /path/to/patch

    c) Recompile your kernel as described in <URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
    system.

    VI. Correction details

    The following list contains the correction revision numbers for each
    affected branch.

    Branch/path Revision
    - ------------------------------------------------------------------------- stable/13/ 894360bacd42f021551f76518edd445f6d299f2e releng/13.0/ 9f00cb5fa8a438e7b9efb2158f2e2edc730badd1 stable/12/ r369312 releng/12.2/ r369353 stable/11/ r369313 releng/11.4/ r369347
    - -------------------------------------------------------------------------

    [FreeBSD 13.x]
    To see which files were modified by a particular revision, run the following command in a checked out git repository, replacing NNNNNN with the revision hash:

    # git show --stat NNNNNN

    Or visit the following URL, replace NNNNNN with the revision hash:

    <URL:https://cgit.freebsd.org/src/commit/?id=NNNNNN>

    [FreeBSD 11.x, FreeBSD 12.x]
    To see which files were modified by a particular revision, run the
    following command, replacing NNNNNN with the revision number, on a
    machine with Subversion installed:

    # svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

    Or visit the following URL, replacing NNNNNN with the revision number:

    <URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

    VII. References

    <URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-25581>

    The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-21:04.jail_remove.asc> -----BEGIN PGP SIGNATURE-----

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