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Index: FreeBSD-EN-23:16.openzfs
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+=============================================================================
+FreeBSD-EN-23:16.openzfs Errata Notice
+ The FreeBSD Project
+
+Topic: OpenZFS data corruption
+
+Category: contrib
+Module: OpenZFS
+Announced: 2023-XX-XX
+Affects: All supported versions of FreeBSD.
+Corrected: 2023-11-28 21:00:48 UTC (stable/14, 14.0-STABLE)
+ 2023-XX-XX XX:XX:XX UTC (releng/14.0, 14.0-RELEASE-pXX)
+ 2023-11-28 21:07:30 UTC (stable/13, 13.2-STABLE)
+ 2023-XX-XX XX:XX:XX UTC (releng/13.2, 13.2-RELEASE-pXX)
+
+NOTE: This also affects FreeBSD 12.4 but the patch is not yet available.
+Once it is available this erratum notice will be updated to include the
+patch for FreeBSD 12.4.
+
+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 has included a version of the powerful and feature-rich ZFS file
+system beginning with FreeBSD 7.0 released in 2008. In FreeBSD 13 and later
+OpenZFS is used as the ZFS implementation.
+
+Sparse files in a file system refer to a technique that optimizes storage
+space by allowing the creation of files with unallocated or unwritten gaps,
+known as holes. When reading a file, holes appear as zero or NUL bytes.
+Certain system calls can access hole location metadata, including lseek(2)
+with SEEK_HOLE and copy_file_range(2).
+
+In OpenZFS a dnode is a data structure used to represent and manage metadata
+about files and directories. In file systems, "dirty" refers to data or
+metadata that has been modified in memory but not yet written to the storage
+device. Thus, a dirty dnode is one which has uncommitted data or metadata.
+
+In FreeBSD 13.2 and FreeBSD 14.0 cp(1) uses copy_file_range(2) to perform the
+data copying in the kernel. copy_file_range attempts to find file holes in
+the source file and preserve them in the copy. In FreeBSD 12.4 cp does not
+use copy_file_range.
+
+II. Problem Description
+
+A check did not test both the dnode itself and its data for dirtiness. This
+provides a very small window of time while a file is being modified where the
+dirtiness check can falsely report that the dnode is clean. If this happens
+a hole may incorrectly be reported where data was written.
+
+III. Impact
+
+If an access occurs while a file is being modified and a hole is incorrectly
+reported, the data may instead be interpreted as zero bytes. Any application
+which checks for holes may be affected by this issue; if this occurs during a
+file copy it will result in a corrupt copy that retains the incorrect data.
+Note that the source file remains intact (a subsequent read will return the
+correct data).
+
+IV. Workaround
+
+Setting the vfs.zfs.dmu_offset_next_sync sysctl to 0 disables forcing
+TXG sync to find holes. This is an effective workaround that greatly
+reduces the likelihood of encountering data corruption, although it does
+not completely eliminate it. Note that with the workaround holes will
+not be reported in recently dirtied files. See the zfs(4) man page for
+more information of the impact of this sysctl setting.
+
+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 platfrom on FreeBSD 13 and earlier, can be updated via
+the freebsd-update(8) utility:
+
+# freebsd-update fetch
+# freebsd-update install
+# shutdown -r +10min "Rebooting to apply OpenZFS 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.
+
+NOTE: The FreeBSD 14.0 patch includes additional bug fixes which were found
+during the investigation of this issue. These bug fixes do not apply to
+FreeBSD 13.2.
+
+[FreeBSD 14.0]
+# fetch https://security.FreeBSD.org/patches/EN-23:16/openzfs.14.patch
+# fetch https://security.FreeBSD.org/patches/EN-23:16/openzfs.14.patch.asc
+# gpg --verify openzfs.14.patch.asc
+
+[FreeBSD 13.2]
+# fetch https://security.FreeBSD.org/patches/EN-23:16/openzfs.13.patch
+# fetch https://security.FreeBSD.org/patches/EN-23:16/openzfs.13.patch.asc
+# gpg --verify openzfs.13.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://docs.freebsd.org/en/books/handbook/kernelconfig/> and reboot the
+system.
+
+VI. Correction details
+
+This issue is corrected as of the corresponding Git commit hash or Subversion
+revision number in the following stable and release branches:
+
+Branch/path Hash Revision
+-------------------------------------------------------------------------
+stable/14/ 99385ec7c296 stable/14-n265836
+releng/14.0/ XXXXXXXXXXXX releng/14.0-nXXXXXX
+stable/13/ 5858f93a8b66 stable/13-n256744
+releng/13.2/ XXXXXXXXXXXX releng/13.2-nXXXXXX
+-------------------------------------------------------------------------
+
+For FreeBSD 13 and later:
+
+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
+
+For FreeBSD 12 and earlier:
+
+Run the following command to see which files were modified by a particular
+revision, replacing NNNNNN with the revision number:
+
+# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base
+
+Or visit the following URL, replacing NNNNNN with the revision number:
+
+<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>
+
+VII. References
+
+<URL:https://bugs.freebsd.org/275308>
+<URL:https://github.com/openzfs/zfs/issues/15526>
+<URL:https://github.com/openzfs/zfs/pull/15566>
+<URL:https://github.com/openzfs/zfs/pull/15571>
+
+The latest revision of this advisory is available at
+<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-23:16.openzfs.asc>

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