Author: cem Date: Fri Oct 30 19:00:42 2020 New Revision: 367181 URL: https://svnweb.freebsd.org/changeset/base/367181
Log: UFS2: Fix DoS due to corrupted extattrfile Prior versions of FreeBSD (11.x) may have produced a corrupt extattr file. (Specifically, r312416 accidentally fixed this defect by removing a strcpy.) CURRENT FreeBSD supports disk images from those prior versions of FreeBSD. Validate the internal structure as soon as we read it in from disk, to prevent these extattr files from causing invariants violations and DoS. Attempting to access the extattr portion of these files results in EINTEGRITY. At this time, the only way to repair files damaged in this way is to copy the contents to another file and move it over the original. PR: 244089 Reported by: Andrea Venturoli <ml AT netfence.it> Reviewed by: kib Discussed with: mckusick (earlier draft) Security: no Differential Revision: https://reviews.freebsd.org/D27010 Modified: head/sys/ufs/ffs/ffs_vnops.c head/sys/ufs/ufs/extattr.h Modified: head/sys/ufs/ffs/ffs_vnops.c ============================================================================== --- head/sys/ufs/ffs/ffs_vnops.c Fri Oct 30 18:55:08 2020 (r367180) +++ head/sys/ufs/ffs/ffs_vnops.c Fri Oct 30 19:00:42 2020 (r367181) @@ -1200,9 +1200,8 @@ ffs_findextattr(u_char *ptr, u_int length, int nspace, eap = (struct extattr *)ptr; eaend = (struct extattr *)(ptr + length); for (; eap < eaend; eap = EXTATTR_NEXT(eap)) { - /* make sure this entry is complete */ - if (EXTATTR_NEXT(eap) > eaend) - break; + KASSERT(EXTATTR_NEXT(eap) <= eaend, + ("extattr next %p beyond %p", EXTATTR_NEXT(eap), eaend)); if (eap->ea_namespace != nspace || eap->ea_namelength != nlen || memcmp(eap->ea_name, name, nlen) != 0) continue; @@ -1216,8 +1215,9 @@ ffs_findextattr(u_char *ptr, u_int length, int nspace, } static int -ffs_rdextattr(u_char **p, struct vnode *vp, struct thread *td, int extra) +ffs_rdextattr(u_char **p, struct vnode *vp, struct thread *td) { + const struct extattr *eap, *eaend, *eapnext; struct inode *ip; struct ufs2_dinode *dp; struct fs *fs; @@ -1231,10 +1231,10 @@ ffs_rdextattr(u_char **p, struct vnode *vp, struct thr fs = ITOFS(ip); dp = ip->i_din2; easize = dp->di_extsize; - if ((uoff_t)easize + extra > UFS_NXADDR * fs->fs_bsize) + if ((uoff_t)easize > UFS_NXADDR * fs->fs_bsize) return (EFBIG); - eae = malloc(easize + extra, M_TEMP, M_WAITOK); + eae = malloc(easize, M_TEMP, M_WAITOK); liovec.iov_base = eae; liovec.iov_len = easize; @@ -1249,8 +1249,18 @@ ffs_rdextattr(u_char **p, struct vnode *vp, struct thr error = ffs_extread(vp, &luio, IO_EXT | IO_SYNC); if (error) { free(eae, M_TEMP); - return(error); + return (error); } + /* Validate disk xattrfile contents. */ + for (eap = (void *)eae, eaend = (void *)(eae + easize); eap < eaend; + eap = eapnext) { + eapnext = EXTATTR_NEXT(eap); + /* Bogusly short entry or bogusly long entry. */ + if (eap->ea_length < sizeof(*eap) || eapnext > eaend) { + free(eae, M_TEMP); + return (EINTEGRITY); + } + } *p = eae; return (0); } @@ -1300,7 +1310,7 @@ ffs_open_ea(struct vnode *vp, struct ucred *cred, stru return (0); } dp = ip->i_din2; - error = ffs_rdextattr(&ip->i_ea_area, vp, td, 0); + error = ffs_rdextattr(&ip->i_ea_area, vp, td); if (error) { ffs_unlock_ea(vp); return (error); @@ -1606,9 +1616,8 @@ vop_listextattr { eap = (struct extattr *)ip->i_ea_area; eaend = (struct extattr *)(ip->i_ea_area + ip->i_ea_len); for (; error == 0 && eap < eaend; eap = EXTATTR_NEXT(eap)) { - /* make sure this entry is complete */ - if (EXTATTR_NEXT(eap) > eaend) - break; + KASSERT(EXTATTR_NEXT(eap) <= eaend, + ("extattr next %p beyond %p", EXTATTR_NEXT(eap), eaend)); if (eap->ea_namespace != ap->a_attrnamespace) continue; Modified: head/sys/ufs/ufs/extattr.h ============================================================================== --- head/sys/ufs/ufs/extattr.h Fri Oct 30 18:55:08 2020 (r367180) +++ head/sys/ufs/ufs/extattr.h Fri Oct 30 19:00:42 2020 (r367181) @@ -95,7 +95,7 @@ struct extattr { * content referenced by eap. */ #define EXTATTR_NEXT(eap) \ - ((struct extattr *)(((u_char *)(eap)) + (eap)->ea_length)) + ((struct extattr *)(__DECONST(char *, (eap)) + (eap)->ea_length)) #define EXTATTR_CONTENT(eap) \ (void *)(((u_char *)(eap)) + EXTATTR_BASE_LENGTH(eap)) #define EXTATTR_CONTENT_SIZE(eap) \ _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
