FreeBSD Security Advisories
2019-Aug-20 20:12 UTC
FreeBSD Security Advisory FreeBSD-SA-19:23.midi
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================FreeBSD-SA-19:23.midi Security Advisory The FreeBSD Project Topic: kernel memory disclosure from /dev/midistat Category: core Module: sound Announced: 2019-08-20 Credits: Peter Holm, Mark Johnston Affects: All supported versions of FreeBSD. Corrected: 2019-08-20 17:53:16 UTC (stable/12, 12.0-STABLE) 2019-08-20 17:50:33 UTC (releng/12.0, 12.0-RELEASE-p10) 2019-08-20 17:54:18 UTC (stable/11, 11.3-STABLE) 2019-08-20 17:50:33 UTC (releng/11.3, 11.3-RELEASE-p3) 2019-08-20 17:50:33 UTC (releng/11.2, 11.2-RELEASE-p14) CVE Name: CVE-2019-5612 For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit <URL:https://security.FreeBSD.org/>. I. Background /dev/midistat is a device file which can be read to obtain a human-readable list of the available MIDI-capable devices in the system. II. Problem Description The kernel driver for /dev/midistat implements a handler for read(2). This handler is not thread-safe, and a multi-threaded program can exploit races in the handler to cause it to copy out kernel memory outside the boundaries of midistat's data buffer. III. Impact The races allow a program to read kernel memory within a 4GB window centered at midistat's data buffer. The buffer is allocated each time the device is opened, so an attacker is not limited to a static 4GB region of memory. On 32-bit platforms, an attempt to trigger the race may cause a page fault in kernel mode, leading to a panic. IV. Workaround No workaround is available. Custom kernels without "device sound" are not vulnerable. V. Solution Upgrade your vulnerable system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date, and reboot. 1) To update your vulnerable system via a binary patch: Systems running a RELEASE version of FreeBSD on the i386 or amd64 platforms can be updated via the freebsd-update(8) utility: # freebsd-update fetch # freebsd-update install # shutdown -r +10min "Rebooting for 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-19:23/midi.patch # fetch https://security.FreeBSD.org/patches/SA-19:23/midi.patch.asc # gpg --verify midi.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 The following list contains the correction revision numbers for each affected branch. Branch/path Revision - ------------------------------------------------------------------------- stable/12/ r351264 releng/12.0/ r351260 stable/11/ r351265 releng/11.3/ r351260 releng/11.2/ r351260 - ------------------------------------------------------------------------- To see which files were modified by a particular revision, run the following command, replacing NNNNNN with the revision number, on a machine with Subversion installed: # 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 <other info on vulnerability> <URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-5612> The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-19:23.midi.asc> -----BEGIN PGP SIGNATURE----- iQKTBAEBCgB9FiEE/A6HiuWv54gCjWNV05eS9J6n5cIFAl1cPgVfFIAAAAAALgAo aXNzdWVyLWZwckBub3RhdGlvbnMub3BlbnBncC5maWZ0aGhvcnNlbWFuLm5ldEZD MEU4NzhBRTVBRkU3ODgwMjhENjM1NUQzOTc5MkY0OUVBN0U1QzIACgkQ05eS9J6n 5cItmQ/9HL5BIP/QUvfcBbhZmZAXa7O7V9Em4auumaUWEPnUaAR0vNKZqMvFXNeN v51/HOwCZte2fCgs8rxSH9ncQR+cUk/3nXO7PZ7pNPNfvuJoPlCV1rIuRrdwm14+ +pZIJpY65gmmXyh5Qa5cw41MEWuDcKluUg38zEROwBpX4h0J/ZuMSARn/s1jj/kJ hy2yzgPTz8gAzkNd8OtQm1CHdFnKWabuAHBlltj9qIA3OvJL+TpIFmzU5jA7wO1n w9GCcz73+IA1RZXu8vPsW9AEc/1LlUrNcyLmJ+bZjW9b7mY9dq+ackvULTzFV21u 5xW2FEX3EBr3kFSbWyIS9zuTX4InftoAr97CBxNMYa25/0En4Ri2rB3oH49BgqTb sr6p5hO3ZB6gOfJIm3WeYIc9dXsqQcWC/Y8hp7zO/Ef29jBHaa76ZX3uGgKGgyoo UcoEjIx4ZpiqQxUEigKdlpEQdUtCIOSZ1NjSYDRFuCURDI07o1Oi8/HSdb9tNRe4 IxfmT7G+oBGbhjZ/bziC/tZX/whXzBdo6eNIBC8XW8hrTDIXVCyqls3igiSqxoFA WMpQN2gEZ6Yug0zpRCn4fj+dvBobpAle7F/gwZdFeWU/wtDiLQHnBOxPaobR56Qy fIoVVGufmnjbSReSGh1WtFhDt+uJ8zal/EqGWi3IBIFpxjhAuP0=I8mB -----END PGP SIGNATURE-----