deadsimple BSD Security Advisories and Announcements

FreeBSD Errata Notice FreeBSD-EN-21:13.mpt

FreeBSD-EN-21:13.mpt                                            Errata Notice
                                                          The FreeBSD Project

Topic:          mpt(4) I/O errors with a large maxphys value

Category:       core
Module:         mpt
Announced:      2021-05-26
Affects:        FreeBSD 13.0
Corrected:      2021-04-24 00:43:14 UTC (stable/13, 13.0-STABLE)
                2021-05-26 19:29:54 UTC (releng/13.0, 13.0-RELEASE-p1)

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I.   Background

mpt(4) is a driver for LSI disk controllers.

II.  Problem Description

The mpt(4) driver did not correctly handle I/O requests larger than or
equal to 2MB and would incorrectly report errors.  The I/O request size
is limited by the value of the kern.maxphys tunable and the default
value is below this threshold.

III. Impact

With kern.maxphys set to 2MB or larger, I/O to mpt(4) devices will not
work correctly.

IV.  Workaround

To work around the problem, ensure that the kern.maxphys value is kept
at its default value.

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, i386, or
(on FreeBSD 13 and later) arm64 platforms can be updated via the
freebsd-update(8) utility:

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

# fetch
# fetch
# gpg --verify mpt.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:> and reboot the

VI.  Correction details

This issue is corrected by the corresponding Git commit hash or Subversion
revision number in the following stable and release branches:

Branch/path                             Hash                     Revision
- -------------------------------------------------------------------------
stable/13/                              f0077b4c1dcf    stable/13-n245384
releng/13.0/                            a8a91efa74e0  releng/13.0-n244734
- -------------------------------------------------------------------------

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:


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