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FreeBSD-EN-26:04.arm64                                          Errata Notice
                                                          The FreeBSD Project

Topic:          Kernel panic when dumping process core on arm64

Category:       core
Module:         arm64
Announced:      2026-02-10
Affects:        FreeBSD 15.0
Corrected:      2026-02-09 16:28:38 UTC (stable/15, 15.0-STABLE)
                2026-02-10 17:56:09 UTC (releng/15.0, 15.0-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

Scalable Vector Extension (SVE) is an extension of the arm64 instruction set
providing SIMD functionality.

II.  Problem Description

When dumping a process core, if SVE is enabled, the kernel will include an ELF
note in the coredump containing the process' SVE register contents.  The
implementation first checks to see if the process has SVE enabled, as part of
pre-calculcating the size of the core dump notes, then checks a second time
when actually populating the note.

III. Impact

The bug could cause a kernel panic.

IV.  Workaround

No workaround is available.  Non-arm64 systems are not affected, and arm64
systems without SVE are not affected.

V.   Solution

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

Perform one of the following:

1) To update your system installed from base system packages:

Systems running a 15.0-RELEASE version of FreeBSD on the amd64 or arm64
platforms, which were installed using base system packages, can be updated
via the pkg(8) utility:

# pkg upgrade -r FreeBSD-base
# shutdown -r +10min "Rebooting for an erratum fix"

2) To update your system installed from binary distribution sets:

Systems running a RELEASE version of FreeBSD on the amd64 or arm64 platforms,
or the i386 platform on FreeBSD 13, which were not installed using base
system packages, can be updated via the freebsd-update(8) utility:

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

3) 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-26:04/arm64.patch
# fetch https://security.FreeBSD.org/patches/EN-26:04/arm64.patch.asc
# gpg --verify arm64.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/15/                              c70a68bbdbf6    stable/15-n282182
releng/15.0/                            539bbdbd3b0c  releng/15.0-n281006
- -------------------------------------------------------------------------

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=292195>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-26:04.arm64.asc>
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