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FreeBSD-SA-17:10.kldstat                                    Security Advisory
                                                          The FreeBSD Project

Topic:          Information leak in kldstat(2)

Category:       core
Module:         kernel
Announced:      2017-11-15
Credits:        TJ Corley
Affects:        All supported versions of FreeBSD.
Corrected:      2017-11-15 22:34:15 UTC (stable/11, 11.1-STABLE)
                2017-11-15 22:49:47 UTC (releng/11.1, 11.1-RELEASE-p4)
                2017-11-15 22:50:20 UTC (releng/11.0, 11.0-RELEASE-p15)
                2017-11-15 22:35:16 UTC (stable/10, 10.4-STABLE)
                2017-11-15 22:50:47 UTC (releng/10.4, 10.4-RELEASE-p3)
                2017-11-15 22:51:08 UTC (releng/10.3, 10.3-RELEASE-p24)
CVE Name:       CVE-2017-1088

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 kldstat(2) syscall provides information about loaded kld files.  The
syscall takes a userland argument of struct kld_file_stat which is then
filled with data about the kld file requested.

II.  Problem Description

The kernel does not properly clear the memory of the kld_file_stat
structure before filling the data.  Since the structure filled by the
kernel is allocated on the kernel stack and copied to userspace, a leak
of information from the kernel stack is possible.

III. Impact

Some bytes from the kernel stack can be observed in userspace.

IV.  Workaround

No workaround is available.

V.   Solution

Perform one of the following:

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

Afterward, reboot the system.

2) 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

Afterward, reboot the system.

3) 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-17:10/kldstat.patch
# fetch https://security.FreeBSD.org/patches/SA-17:10/kldstat.patch.asc
# gpg --verify kldstat.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/10/                                                        r325867
releng/10.3/                                                      r325878
releng/10.4/                                                      r325877
stable/11/                                                        r325866
releng/11.0/                                                      r325876
releng/11.1/                                                      r325875
- -------------------------------------------------------------------------

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-2017-1088>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-17:10.kldstat.asc>
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