CVE-2023-6660

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-SA-23:18.nfsclient Security Advisory The FreeBSD Project Topic: NFS client data corruption and kernel memory disclosure Category: core Module: nfsclient Announced: 2023-12-12 Credits: Hostpoint AG Affects: FreeBSD 13.2 and 14.0 Corrected: 2023-12-12 19:13:50 UTC (stable/14, 14.0-STABLE) 2023-12-12 19:17:36 UTC (releng/14.0, 14.0-RELEASE-p3) 2023-12-12 19:14:16 UTC (stable/13, 13.2-STABLE) 2023-12-12 19:18:17 UTC (releng/13.2, 13.2-RELEASE-p8) CVE Name: CVE-2023-6660 For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit . I. Background The Network File System (NFS) is a distributed file system that allows remote systems to access files and directories over a network as if they were local. FreeBSD includes both server and client implementations of NFS. II. Problem Description In FreeBSD 13.2 and 14.0, the NFS client was optimized to improve the performance of IO_APPEND writes, that is, writes which add data to the end of a file and so extend its size. This uncovered an old bug in some routines which copy userspace data into the kernel. The bug also affects the NFS client’s implementation of direct I/O; however, this implementation is disabled by default by the vfs.nfs.nfs_directio_enable sysctl and is only used to handle synchronous writes. III. Impact When a program running on an affected system appends data to a file via an NFS client mount, the bug can cause the NFS client to fail to copy in the data to be written but proceed as though the copy operation had succeeded. This means that the data to be written is instead replaced with whatever data had been in the packet buffer previously. Thus, an unprivileged user with access to an affected system may abuse the bug to trigger disclosure of sensitive information. In particular, the leak is limited to data previously stored in mbufs, which are used for network transmission and reception, and for certain types of inter-process communication. The bug can also be triggered unintentionally by system applications, in which case the data written by the application to an NFS mount may be corrupted. Corrupted data is written over the network to the NFS server, and thus also susceptible to being snooped by other hosts on the network. Note that the bug exists only in the NFS client; the version and implementation of the server has no effect on whether a given system is affected by the problem. IV. Workaround No workaround is available. V. Solution Upgrade your vulnerable 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 vulnerable 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 for a security update” 2) To update your vulnerable 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/SA-23:18/nfsclient.patch # fetch https://security.FreeBSD.org/patches/SA-23:18/nfsclient.patch.asc # gpg --verify nfsclient.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 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/ 8d42f85d9d7b stable/14-n265954 releng/14.0/ ab60666a00c9 releng/14.0-n265397 stable/13/ f1d1d50e1d08 stable/13-n256860 releng/13.2/ 3f079b3f2f33 releng/13.2-n254649 - ------------------------------------------------------------------------- Run the following command to see which files were modified by a particular commit: # git show --stat 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 -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEthUnfoEIffdcgYM7bljekB8AGu8FAmV4s/kACgkQbljekB8A Gu8kvg//RUe/q2SFiVyo94disTET5JjVAPjKzMrHuhoI92OA994zS3MXmU6cQZAh ikWzMTf25/tgGvN8/Cujhp6zIXiPwUvwJXQqL6JN2/lqHHztxYz/m3Ol8Pc2q2yx hDbY0dOeyaGK9CuH7hjMtu/jeh6vj+TyvzLg/KuxgdOkjdDd352CF43alkb5Q55t 3V8pcY49zCk+5aMJv667mphGxf4yRC/+bkVtJIqoAUpAg/VORMJmMiEt0LS3v7t5 Oaal8rVfcPu8jPhkt8dIzcp1lrr+AfsOnEB68x2ECiYp2LCWp/ya7rG+DMD537kw IhSKRpqMvc4rQpjGQIsewO+sexyYC/zYrUu4BYMUnLVEqQ+GPN7jV7uAjoGuvsus uOAuN3l4T1x50VyBGA9Z2sVAHOkDAh98J8HDtdCK+IxNnTKFsFHBE/4zFLXkVYwr vo15qZpHzdTnHhhq5GjxZU+j1Sw0TbMWYPVPsgv8HqZciPjmv5bW7nxvB60sqb1a LYhE2cWilWxNKWQLhFt60ooGb09Auu+wDgnXLmTmpc/phOI+hCNOPedRF/0yPS7D dE0Q1vjdoiJgcAdntve8fzlwq1KSG4mQZRrJvMverW+/YLtbEFYY/iFT+jYWRMcN QwyjgbABQ9tzOVaPjSGJp/UB7SjDn8KFoOfeXWZrMkOYz95lXUk= =Wsy4 -----END PGP SIGNATURE-----