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FreeBSD-EN-24:10.zfs                                            Errata Notice
                                                          The FreeBSD Project

Topic:          Kernel memory leak in ZFS

Category:       core
Module:         openzfs
Announced:      2024-06-19
Affects:        FreeBSD 14.1
Corrected:      2024-06-17 14:35:24 UTC (stable/14, 14.1-STABLE)
                2024-06-19 20:36:48 UTC (releng/14.1, 14.1-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 originally developed by Sun
Microsystems for its Solaris operating system. ZFS was integrated as part of
the FreeBSD starting with FreeBSD 7.0, and it has since become a prominent
and preferred choice for storage management.

II.  Problem Description

When writing data to a file on ZFS, the kernel may need to handle soft
page faults that can occur when accessing user data.  When doing so, in
some cases ZFS needs to undo an earlier kernel buffer allocation.  A bug
in the handling of these cases causes this buffer to be leaked.

III. Impact

The leaked kernel memory is effectively lost and cannot be reused for
other purposes.  Some workloads may trigger the leak frequently,
eventually requiring a reboot of the system.

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.

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
# reboot

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-24:10/zfs.patch
# fetch https://security.FreeBSD.org/patches/EN-24:10/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/14/                              1c27279ed22d    stable/14-n267965
releng/14.1/                            f566b7eb8d94  releng/14.1-n267680
- -------------------------------------------------------------------------

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=276341>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-24:10.zfs.asc>
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