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FreeBSD-EN-25:19.zfs                                            Errata Notice
                                                          The FreeBSD Project

Topic:          Unprivileged kernel NULL pointer dereference

Category:       contrib
Module:         openzfs
Announced:      2025-12-16
Credits:        Collin Funk
Affects:        FreeBSD 15.0
Corrected:      2025-12-15 14:16:12 UTC (stable/15, 15.0-STABLE)
                2025-12-16 23:42:59 UTC (releng/15.0, 15.0-RELEASE-p1)

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

ZFS is an advanced and scalable file system that is commonly used on FreeBSD.

II.  Problem Description

Invoking the fsync(2) system call on a named pipe will trigger a NULL pointer
dereference in the kernel, causing a system panic.

III. Impact

A malicious, unprivileged user may be able to panic the system.

Software which attempts to fsync a named pipe may inadvertently panic the
system.

IV.  Workaround

No workaround is available.  Systems not using ZFS are unaffected.

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
can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install
# shutdown -r now

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-25:19/zfs.patch
# fetch https://security.FreeBSD.org/patches/EN-25:19/zfs.patch.asc
# gpg --verify zfs.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/                              d988a0c1fc4c    stable/15-n281511
releng/15.0/                            ff6b9c7c1c34  releng/15.0-n280996
- -------------------------------------------------------------------------

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-25:19.zfs.asc>
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