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FreeBSD-SA-22:11.vm                                         Security Advisory
                                                          The FreeBSD Project

Topic:          Memory disclosure by stale virtual memory mapping

Category:       core
Module:         vm
Announced:      2022-08-09
Credits:        Mark Johnston
Affects:        All supported versions of FreeBSD.
Corrected:      2022-08-09 19:47:40 UTC (stable/13, 13.1-STABLE)
                2022-08-09 20:01:00 UTC (releng/13.1, 13.1-RELEASE-p1)
                2022-08-09 19:59:49 UTC (releng/13.0, 13.0-RELEASE-p12)
                2022-08-09 19:57:38 UTC (stable/12, 12.3-STABLE)
                2022-08-09 19:59:48 UTC (releng/12.3, 12.3-RELEASE-p6)
CVE Name:       CVE-2022-23091

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

Memory mappings shared between processes are a feature of the FreeBSD
virtual memory system.  They may be established by unprivileged
processes with the mmap(2), fork(2), and other system calls.

II.  Problem Description

A particular case of memory sharing is mishandled in the virtual memory
system.  This is very similar to SA-21:08.vm, but with a different root
cause.

III. Impact

An unprivileged local user process can maintain a mapping of a page
after it is freed, allowing that process to read private data belonging
to other processes or the kernel.

IV.  Workaround

No workaround is available.

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 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 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.

# fetch https://security.FreeBSD.org/patches/SA-22:11/vm.patch
# fetch https://security.FreeBSD.org/patches/SA-22:11/vm.patch.asc
# gpg --verify vm.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/                              3ea8c7ad90f7    stable/13-n252080
releng/13.1/                            0c88ecaa1255  releng/13.1-n250153
releng/13.0/                            dd349089ff92  releng/13.0-n244805
stable/12/                                                        r372377
releng/12.3/                                                      r372381
- -------------------------------------------------------------------------

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

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-23091>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-22:11.vm.asc>
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