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=============================================================================
FreeBSD-EN-24:05.tty                                           Erratum Notice
                                                          The FreeBSD Project

Topic:          TTY Kernel Panic

Category:       core
Module:         kernel
Announced:      2024-03-28
Affects:        FreeBSD 13.2 and FreeBSD 14.0
Corrected:      2024-02-29 00:29:13 UTC (stable/14, 14.0-STABLE)
                2024-03-28 05:06:21 UTC (releng/14.0, 14.0-RELEASE-p6)
                2024-02-29 00:30:12 UTC (stable/13, 13.2-STABLE)
                2024-03-28 05:07:53 UTC (releng/13.2, 13.2-RELEASE-p11)

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

tty(4) is the general terminal device.  The kern.ttys sysctl provides tty
information for tools such as `pstat -t`.

FreeBSD-SA-24:02.tty addressed an information leak about outside processes
from within a jail.

II.  Problem Description

A missing check resulted in a null pointer dereference if a tty had a session
associated, but no session leader.

III. Impact

Under certain conditions an unprivileged user could provoke a kernel panic.

IV.  Workaround

No workaround is available.

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 or arm64 platforms,
or the i386 platform on FreeBSD 13, 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-24:05/tty.patch
# fetch https://security.FreeBSD.org/patches/EN-24:05/tty.patch.asc
# gpg --verify tty.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 as of the corresponding Git commit hash in the
following stable and release branches:

Branch/path                             Hash                     Revision
- -------------------------------------------------------------------------
stable/14/                              8d22744f5be1    stable/14-n266915
releng/14.0/                            a3ec3054762f  releng/14.0-n265411
stable/13/                              a60220bbb551    stable/13-n257543
releng/13.2/                            f3195cc08ccc  releng/13.2-n254662
- -------------------------------------------------------------------------

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

VII. References

<URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=277240>
<URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=277329>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-24:05.tty.asc>
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