NetBSD Security Advisory 2022-002: Coredump credential reference count leak
4 October, 2022 by security-officer@netbsd.org | netbsd
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 NetBSD Security Advisory 2022-002 ================================= Topic: Coredump credential reference count leak Version: NetBSD-current: affected prior to 2022-09-10 NetBSD 9.2: affected NetBSD 8.2: affected Severity: Malicious user may read from opened file descriptors by other processes. Fixed: NetBSD-current: September 10, 2022 NetBSD-9 branch: September 10, 2022 NetBSD-8 branch: September 10, 2022 Please note that NetBSD releases prior to 8 are no longer supported. It is recommended that all users upgrade to a supported release. Abstract ======== The coredump handling code always leaks a reference to the dumped processes cred structure. An attacker may cause the reference count to overflow, leading to a use after free (UAF). Solutions and Workarounds ========================= Set the coredump resource limit to 0 to prevent coredumps in the system. To apply a fixed version from a releng build, fetch a fitting kern-GENERIC.tgz from nycdn.NetBSD.org and extract the fixed binaries: cd /var/tmp ftp https://nycdn.NetBSD.org/pub/NetBSD-daily/REL/BUILD/ARCH/binary/sets/kern-GENERIC.tgz cd / tar xzpf /var/tmp/kern-GENERIC.tgz with the following replacements: REL = the release version you are using BUILD = the source date of the build. 20220910 and later will fit ARCH = your system's architecture The following instructions describe how to upgrade your kernel by updating your source tree and rebuilding and installing a new version of the kernel. For all NetBSD versions, you need to obtain fixed kernel sources, rebuild and install the new kernel, and reboot the system. The fixed source may be obtained from the NetBSD CVS repository. The following instructions briefly summarise how to upgrade your kernel. In these instructions, replace: ARCH with your architecture (from uname -m), and KERNCONF with the name of your kernel configuration file. To update from CVS, re-build, and re-install the kernel: # cd src # cvs update -d -P sys/miscfs/procfs/procfs_vnops.c # ./build.sh kernel=KERNCONF # mv /netbsd /netbsd.old # cp sys/arch/ARCH/compile/obj/KERNCONF/netbsd /netbsd # shutdown -r now For more information on how to do this, see: https://www.NetBSD.org/docs/guide/en/chap-kernel.html Thanks To ========= Chris J-D <chris@accessvector.net> for discovering, analyzing the problem and proposing a fix. Revision History ================ 2022-10-02 Initial release More Information ================ Advisories may be updated as new information becomes available. The most recent version of this advisory (PGP signed) can be found at https://cdn.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2022-002.txt.asc Information about NetBSD and NetBSD security can be found at https://www.NetBSD.org/ https://www.NetBSD.org/support/security/ Copyright 2022, The NetBSD Foundation, Inc. All Rights Reserved. Redistribution permitted only in full, unmodified form. $Id: NetBSD-SA2022-002.txt,v 1.1 2022/10/02 14:02:28 christos Exp $ -----BEGIN PGP SIGNATURE----- iQJQBAEBCAA6FiEEJxEzJivzXLUNT1BGiSYeF/XvSf8FAmM5mfUcHHNlY3VyaXR5 LW9mZmljZXJAbmV0YnNkLm9yZwAKCRCJJh4X9e9J/xrHD/0Wbq+Udq/u0cuF97kH /3MOresRMPCTg8TOjvC88ONJOwCU/qh7txV/STIHD+HBOsLu47DbcFzKTJjIsiGQ fTeeMIs3WH04J4+kEzJtmUxvRfp0Yvy2LmOnn1hWh9iUEOm+k4U8eWnOzo6PTlli 10mz8WaNRA/aMbUsPlL9dSn/c8InGVxJvSR1w1K8O+nox+E08QCymO/mO+V70K/E VTlf9zQwZU02J2k2hChGHjBJKh/VvdG5He5pyTT9a9aTnSxwwZkdJE7+GuyLmhSg D9rp5mJo+TAeY4kn5SAiByaullc+uwfg1dfr2D81Qp9rFIYCjWPYJpFrN0XTVhVk j+eCWX0FSCD/qdUUDLp67coF2EgoDkKo8NxPoxE2AR6N9covcwAmi4E8CGsO4+Kl WEAuaoSOQvdU/nBms8VH0BWYWzmVwq3sk2gHHXw88r1dNjhsJ/ojiyOWOt2yP6uE gceCFY+qaTrAo5hGgcOLh9EzfDzSrq3f/8fFwLuZeeDVQsmVhg0ltRVi9eNIXr/2 qxp4RBPB7bINHQR7uT/9hyFXxp4+SsWSzau+9Z61Z6WXEA7i24jHXUvTtTTqSa/r T+znbCJ8M07oU4TSG3dR4VmILwebHvW/zVZfsE8KzA/o5A30wSRkoRGIjULMd5iY gmObL5NqCIwT81wHOoPk2Kz6oA== =RXBd -----END PGP SIGNATURE-----