---------- Forwarded message ---------- Date: Thu, 4 Jun 1998 19:56:36 +0200 (MET DST) From: FreeBSD Security Officer <security-officerat_private> To: undisclosed-recipients:;@FreeBSD.ORG Subject: FreeBSD Security Advisory: FreeBSD-SA-98:05.nfs -----BEGIN PGP SIGNED MESSAGE----- ============================================================================= FreeBSD-SA-98:05 Security Advisory FreeBSD, Inc. Topic: system crash with NFS Category: core Module: kernel Announced: 1998-06-04 Affects: FreeBSD 2.2.* and FreeBSD-stable before 1998/05/31 this problem. Corrected: FreeBSD-current as of 1998/05/31 FreeBSD only: no (also other 4.4BSD based systems may be affected) Patches: ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-98:05/ ============================================================================= IMPORTANT MESSAGE: The FreeBSD security officer now uses the policy ftp://ftp.freebsd.org/pub/FreeBSD/POLICY.asc for sending out advisories. ============================================================================= I. Background NFS can be used to mount remote file systems. Apart from being remote, it acts like a normal UFS file system. Among others, This means that creating hard links can be done in NFS file systems II. Problem Description When creating hard links on file systems, the kernel checks that both the original file and the link to it are located on the same file system. Unfortunately, there is an error in the NFS kernel code in FreeBSD 2.2.* systems that performs this check. III. Impact It is possible to crash a FreeBSD 2.2.* system by hard linking a device special files to a file on an NFS mounted file system. FreeBSD-current is not vulnerable. IV. Workaround No real work around is known (except for unmounting your NFS file systems). V. Solution Apply one of the following patches, rebuild your kernel, install it and reboot your system. The patches below can be found on ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-98:05/ Patch for 2.2.5 and 2.2.6 systems: Index: nfs_vnops.c =================================================================== RCS file: /home/cvsup/freebsd/CVS/src/sys/nfs/nfs_vnops.c,v retrieving revision 1.36.2.6 retrieving revision 1.36.2.7 diff -u -r1.36.2.6 -r1.36.2.7 --- nfs_vnops.c 1998/05/13 05:48:45 1.36.2.6 +++ nfs_vnops.c 1998/05/31 00:07:29 1.36.2.7 @@ -1755,17 +1755,8 @@ struct componentname *a_cnp; } */ *ap; { -#if defined(__NetBSD__) - /* - * Since the args are reversed in the VOP_LINK() calls, - * switch them back. Argh! - */ - register struct vnode *vp = ap->a_tdvp; - register struct vnode *tdvp = ap->a_vp; -#else register struct vnode *vp = ap->a_vp; register struct vnode *tdvp = ap->a_tdvp; -#endif register struct componentname *cnp = ap->a_cnp; register u_long *tl; register caddr_t cp; @@ -1776,11 +1767,8 @@ int v3 = NFS_ISV3(vp); if (vp->v_mount != tdvp->v_mount) { - VOP_ABORTOP(vp, cnp); - if (tdvp == vp) - vrele(tdvp); - else - vput(tdvp); + VOP_ABORTOP(tdvp, cnp); + vput(tdvp); return (EXDEV); } ============================================================================= FreeBSD, Inc. Web Site: http://www.freebsd.org/ Confidential contacts: security-officerat_private Security notifications: security-notificationsat_private Security public discussion: freebsd-securityat_private PGP Key: ftp://ftp.freebsd.org/pub/FreeBSD/CERT/public_key.asc Notice: Any patches in this document may not apply cleanly due to modifications caused by digital signature or mailer software. Please reference the URL listed at the top of this document for original copies of all patches if necessary. ============================================================================= -----BEGIN PGP SIGNATURE----- Version: 2.6.3ia Charset: noconv iQCVAwUBNXbehFUuHi5z0oilAQHS8gQAgIgUrioo3hT+mJLyxUp//ASoFPSf2+vw fmq2D9qEYyV5Od/HLBnzgb3jz5xyqWDLBx6pNV3QIPAimw3+S0oHOUYG+UCn96yD 58kEx6mc8KanEHs0lzdgoqFi6ioVkPzCplxzqy+QfQvDCJPE+w7BbFkwVXhJHNof 4JvVbewoA9c= =ILgB -----END PGP SIGNATURE----- To Unsubscribe: send mail to majordomoat_private with "unsubscribe security" in the body of the message
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