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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2005.0892 -- NetBSD Security Advisory 2005-012 SO_LINGER argument checking DIAGNOSTIC panic 8 November 2005 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: kernel (SO_LINGER socket option) Publisher: NetBSD Operating System: NetBSD-current (source prior to October 21, 2005) NetBSD 2.1 NetBSD 2.0.3 NetBSD 2.0 Impact: Denial of Service Access: Existing Account Original Bulletin: ftp://ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2005-012.txt.asc - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 NetBSD Security Advisory 2005-012 ================================= Topic: SO_LINGER argument checking DIAGNOSTIC panic Version: NetBSD-current: source prior to October 21, 2005 NetBSD 2.1: affected NetBSD 2.0.3: affected NetBSD 2.0: affected NetBSD 1.6: not affected Severity: local denial-of-service crash by unprivileged user Fixed: NetBSD-current: October 21, 2005 NetBSD-3 branch: October 21, 2005 NetBSD-2.1 branch: October 31, 2005 (2.1.1 will include the fix) NetBSD-2.0 branch: October 31, 2005 (2.0.4 will include the fix) NetBSD-2 branch: October 21, 2005 Abstract ======== The SO_LINGER socket option can be passed negative a linger time, which can be used by an unprivileged user to trigger a kernel assertion panic if the kernel is compiled with "options DIAGNOSTIC". Technical Details ================= The socket option SO_LINGER, accessed through setsockopt(3), takes a structure containing the linger time, in seconds. This linger time argument was not being bounds checked carefully enough. If you pass a negative linger time and enable the socket option, soclose() calls tsleep() with a timeout of that negative time * hz. The same problem occurs if the number of seconds times hz overflows INT_MAX. In a DIAGNOSTIC kernel, KASSERT() in callout_reset() fires when it receives the negative value, triggering a panic. With DIAGNOSTIC off, this appears to be harmless. The SO_LINGER time argument has never been properly bounds checked, however the potential crash was introduced together with a new callout implementation introduced in NetBSD-current at 1.6N, after the 1.6 release was branched. In that implementation, a KASSERT() was called on all timeout values to catch cases such as this, instead of silently bumping any negative value up to 1. Therefore, releases 1.6 and prior, and non-DIAGNOSTIC kernels, cannot be used to trigger a crash in this manner. The additional consistency checks enabled by this option are somewhat expensive, and can trigger crash dumps for analysis should they fire, as in this case. Therefore, DIAGNOSTIC is not recommended for use on production systems, though it may well be desirable on development or test systems. A number of NetBSD ports ship GENERIC or other kernel configurations with DIAGNOSTIC enabled. Solutions and Workarounds ========================= Users running kernels without "options DIAGNOSTIC" are not affected, and need take no action. For affected systems, the kernel must be rebuilt to remove the vulnerability - either by removing the DIAGNOSTIC option from your kernel config, or by updating the kernel sources to include the fix for additional bounds checking (or both). For all affected 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/kern/uipc_socket.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: http://www.netbsd.org/guide/en/chap-kernel.html Thanks To ========= Nathan J. Williams for finding and fixing the issue. Revision History ================ 2005-11-01 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 ftp://ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2005-012.txt.asc Information about NetBSD and NetBSD security can be found at http://www.NetBSD.org/ and http://www.NetBSD.org/Security/. Copyright 2005, The NetBSD Foundation, Inc. All Rights Reserved. Redistribution permitted only in full, unmodified form. $NetBSD: NetBSD-SA2005-012.txt,v 1.4 2005/11/02 04:34:23 dan Exp $ - -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (NetBSD) iQCVAwUBQ2hB4z5Ru2/4N2IFAQKmhwP/aaVSETU8tRkkvdyJJM1OR3qCp/NkdmTk hUl+kfW/+3TVN28DxXSOxtoG/K15FJ/gY2bvYNAooK/pBem6WU+wrILsItDeTc9C wifrPjps2gkPuNbZDF3K5NJyu/77i92VSMHWWIBIG8UFULGza5T4OvEoXTP2Fv6K poBCPmkcTuA= =wyTe - -----END PGP SIGNATURE----- - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. 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Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/render.html?cid=1980 If you believe that your computer system has been compromised or attacked in any way, we encourage you to let us know by completing the secure National IT Incident Reporting Form at: http://www.auscert.org.au/render.html?it=3192 =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: firstname.lastname@example.org Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQCVAwUBQ2/5CSh9+71yA2DNAQKtFQP+Nt1BbqsIR/QWOv2DIDZOxG0xPr7xcY4J xqbSRdocxIThzLwYvrARPrq9St5gBl0APeDaWu3xBmsLiSsYWn+v809thuYJdmRp xhmhH19YtyGPku/j5DEGDKWPQ/aOP+4wmrXFB4sRk3m3e0VUy2I0diTkDlTUML1b rgMW3eJ6g8A= =9UB/ -----END PGP SIGNATURE-----