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  • [FreeBSD-Announce] FreeBSD Errata Notice FreeBSD-EN-21:21.ipfw

    From FreeBSD Errata Notices@21:1/5 to All on Fri Sep 17 15:45:07 2021
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    ============================================================================= FreeBSD-EN-21:21.ipfw Errata Notice
    The FreeBSD Project

    Topic: Kernel panic with ipfw link-layer filtering enabled

    Category: core
    Module: ipfw
    Announced: 2021-06-29
    Affects: FreeBSD 13.0
    Corrected: 2021-06-19 14:08:49 UTC (stable/13, 13.0-STABLE)
    2021-06-29 17:09:43 UTC (releng/13.0, 13.0-RELEASE-p3)

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

    I. Background

    ipfw(4) is a IP packet filter implementation in the kernel. It uses the pfil(9) interface to hook into several

    II. Problem Description

    When link-layer filtering is enabled by setting the net.link.ether.ipfw
    sysctl to 1, packets received by the filter may be reallocated to ensure
    that protocol headers are contiguous in memory. In this case, the old
    copy of the packet is freed. However, the filter failed to update the
    pointer returned to the pfil(9) caller, resulting in the use of a
    pointer to freed memory.

    III. Impact

    Systems which use ipfw(4)'s link-layer filtering capabilities may panic.

    IV. Workaround

    No workaround is available. Systems not using ipfw(4), or systems that
    do not explicitly enable link-layer filtering by setting the net.link.ether.ipfw sysctl to 1, are not affected.

    V. Solution

    Upgrade your 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 system via a binary patch:

    Systems running a RELEASE version of FreeBSD on the amd64, i386, or
    (on FreeBSD 13 and later) arm64 platforms can be updated via the freebsd-update(8) utility:

    # freebsd-update fetch
    # freebsd-update install
    # shutdown -r +10min "Rebooting for an erratum update"

    2) To update your 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.

    # fetch https://security.FreeBSD.org/patches/EN-21:21/ipfw.patch
    # fetch https://security.FreeBSD.org/patches/EN-21:21/ipfw.patch.asc
    # gpg --verify ipfw.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

    This issue is corrected by the corresponding Git commit hash or Subversion revision number in the following stable and release branches:

    Branch/path Hash Revision
    - ------------------------------------------------------------------------- stable/13/ ed1acef3fe30 stable/13-n246063 releng/13.0/ 4647d115ff84 releng/13.0-n244750
    - -------------------------------------------------------------------------

    For FreeBSD 13 and later:

    Run the following command to see which files were modified by a
    particular commit:

    # git show --stat <commit hash>

    Or visit the following URL, replacing NNNNNN with the hash:

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

    To determine the commit count in a working tree (for comparison against
    nNNNNNN in the table above), run:

    # git rev-list --count --first-parent HEAD

    For FreeBSD 12 and earlier:

    Run the following command to see which files were modified by a particular revision, replacing NNNNNN with the revision number:

    # 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

    <other info on the problem>

    <URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=254015>

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

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