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FreeBSD-EN-26:16.arm64 Errata Notice
The FreeBSD Project
Topic: 32-bit setcontext(2) and swapcontext(2) fail on arm64
Category: core
Module: arm64
Announced: 2026-06-30
Affects: All supported versions of FreeBSD.
Corrected: 2026-06-29 08:11:12 UTC (stable/15, 15.1-STABLE)
2026-06-30 17:21:50 UTC (releng/15.1, 15.1-RELEASE-p1)
2026-06-30 17:21:18 UTC (releng/15.0, 15.0-RELEASE-p11)
2026-06-29 08:14:41 UTC (stable/14, 14.4-STABLE)
2026-06-30 17:20:53 UTC (releng/14.4, 14.4-RELEASE-p7)
2026-06-30 17:20:26 UTC (releng/14.3, 14.3-RELEASE-p16)
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
FreeBSD/arm64 supports running 32-bit (armv7) binaries via its
freebsd32 compatibility layer.
The setcontext(2) and swapcontext(2) system calls allow a process to
save and restore its execution context.
II. Problem Description
The freebsd32 implementations of setcontext(2) and swapcontext(2) on
arm64 returned incorrect values on success, causing the system call to
be treated as though it had failed.
III. Impact
32-bit armv7 applications that use setcontext(2) or swapcontext(2)
may crash or behave incorrectly when running on arm64 hosts. This
has been observed to cause random crashes in Ruby applications in
particular.
IV. Workaround
No workaround is available. Systems that do not run 32-bit armv7
binaries on arm64 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 installed from base system packages:
Systems running a 15.0-RELEASE or later 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 now
2) To update your system installed from binary distribution sets:
Systems running a RELEASE version of FreeBSD on the amd64 or arm64 platforms
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 now
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-26:16/arm64.patch
# fetch https://security.FreeBSD.org/patches/EN-26:16/arm64.patch.asc
# gpg --verify arm64.patch.asc
b) Apply the patch. Execute the following commands as root:
# cd /usr/src
# patch -E -p0 < /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/ 964215aa1347 stable/15-n284267
releng/15.1/ a2235baa622b releng/15.1-n283563
releng/15.0/ b77d19dcc0d5 releng/15.0-n281065
stable/14/ 58a15fe75cc5 stable/14-n274442
releng/14.4/ f902821db095 releng/14.4-n273727
releng/14.3/ e96d0e1fccf5 releng/14.3-n271527
- -------------------------------------------------------------------------
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
The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-26:16.arm64.asc>
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