diff options
Diffstat (limited to 'freebsd/sys/kern/vfs_lookup.c')
| -rw-r--r-- | freebsd/sys/kern/vfs_lookup.c | 1450 |
1 files changed, 1450 insertions, 0 deletions
diff --git a/freebsd/sys/kern/vfs_lookup.c b/freebsd/sys/kern/vfs_lookup.c new file mode 100644 index 00000000..5ee3f219 --- /dev/null +++ b/freebsd/sys/kern/vfs_lookup.c @@ -0,0 +1,1450 @@ +/*- + * SPDX-License-Identifier: BSD-3-Clause + * + * Copyright (c) 1982, 1986, 1989, 1993 + * The Regents of the University of California. All rights reserved. + * (c) UNIX System Laboratories, Inc. + * All or some portions of this file are derived from material licensed + * to the University of California by American Telephone and Telegraph + * Co. or Unix System Laboratories, Inc. and are reproduced herein with + * the permission of UNIX System Laboratories, Inc. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * + * @(#)vfs_lookup.c 8.4 (Berkeley) 2/16/94 + */ + +#include <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include "opt_capsicum.h" +#include "opt_ktrace.h" + +#include <sys/param.h> +#include <sys/systm.h> +#include <sys/kernel.h> +#include <sys/capsicum.h> +#include <sys/fcntl.h> +#include <sys/jail.h> +#include <sys/lock.h> +#include <sys/mutex.h> +#include <sys/namei.h> +#include <sys/vnode.h> +#include <sys/mount.h> +#include <sys/filedesc.h> +#include <sys/proc.h> +#include <sys/sdt.h> +#include <sys/syscallsubr.h> +#include <sys/sysctl.h> +#ifdef KTRACE +#include <sys/ktrace.h> +#endif + +#include <security/audit/audit.h> +#include <security/mac/mac_framework.h> + +#include <vm/uma.h> + +#define NAMEI_DIAGNOSTIC 1 +#undef NAMEI_DIAGNOSTIC + +SDT_PROVIDER_DECLARE(vfs); +SDT_PROBE_DEFINE3(vfs, namei, lookup, entry, "struct vnode *", "char *", + "unsigned long"); +SDT_PROBE_DEFINE2(vfs, namei, lookup, return, "int", "struct vnode *"); + +/* Allocation zone for namei. */ +uma_zone_t namei_zone; + +/* Placeholder vnode for mp traversal. */ +static struct vnode *vp_crossmp; + +static int +crossmp_vop_islocked(struct vop_islocked_args *ap) +{ + + return (LK_SHARED); +} + +static int +crossmp_vop_lock1(struct vop_lock1_args *ap) +{ + struct vnode *vp; + struct lock *lk __unused; + const char *file __unused; + int flags, line __unused; + + vp = ap->a_vp; + lk = vp->v_vnlock; + flags = ap->a_flags; + file = ap->a_file; + line = ap->a_line; + + if ((flags & LK_SHARED) == 0) + panic("invalid lock request for crossmp"); + + WITNESS_CHECKORDER(&lk->lock_object, LOP_NEWORDER, file, line, + flags & LK_INTERLOCK ? &VI_MTX(vp)->lock_object : NULL); + WITNESS_LOCK(&lk->lock_object, 0, file, line); + if ((flags & LK_INTERLOCK) != 0) + VI_UNLOCK(vp); + LOCK_LOG_LOCK("SLOCK", &lk->lock_object, 0, 0, ap->a_file, line); + return (0); +} + +static int +crossmp_vop_unlock(struct vop_unlock_args *ap) +{ + struct vnode *vp; + struct lock *lk __unused; + int flags; + + vp = ap->a_vp; + lk = vp->v_vnlock; + flags = ap->a_flags; + + if ((flags & LK_INTERLOCK) != 0) + VI_UNLOCK(vp); + WITNESS_UNLOCK(&lk->lock_object, 0, LOCK_FILE, LOCK_LINE); + LOCK_LOG_LOCK("SUNLOCK", &lk->lock_object, 0, 0, LOCK_FILE, + LOCK_LINE); + return (0); +} + +static struct vop_vector crossmp_vnodeops = { + .vop_default = &default_vnodeops, + .vop_islocked = crossmp_vop_islocked, + .vop_lock1 = crossmp_vop_lock1, + .vop_unlock = crossmp_vop_unlock, +}; + +struct nameicap_tracker { + struct vnode *dp; + TAILQ_ENTRY(nameicap_tracker) nm_link; +}; + +/* Zone for cap mode tracker elements used for dotdot capability checks. */ +static uma_zone_t nt_zone; + +static void +nameiinit(void *dummy __unused) +{ + + namei_zone = uma_zcreate("NAMEI", MAXPATHLEN, NULL, NULL, NULL, NULL, + UMA_ALIGN_PTR, 0); + nt_zone = uma_zcreate("rentr", sizeof(struct nameicap_tracker), + NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); + getnewvnode("crossmp", NULL, &crossmp_vnodeops, &vp_crossmp); +} +SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nameiinit, NULL); + +static int lookup_cap_dotdot = 1; +SYSCTL_INT(_vfs, OID_AUTO, lookup_cap_dotdot, CTLFLAG_RWTUN, + &lookup_cap_dotdot, 0, + "enables \"..\" components in path lookup in capability mode"); +static int lookup_cap_dotdot_nonlocal = 1; +SYSCTL_INT(_vfs, OID_AUTO, lookup_cap_dotdot_nonlocal, CTLFLAG_RWTUN, + &lookup_cap_dotdot_nonlocal, 0, + "enables \"..\" components in path lookup in capability mode " + "on non-local mount"); + +static void +nameicap_tracker_add(struct nameidata *ndp, struct vnode *dp) +{ + struct nameicap_tracker *nt; + + if ((ndp->ni_lcf & NI_LCF_CAP_DOTDOT) == 0 || dp->v_type != VDIR) + return; + nt = uma_zalloc(nt_zone, M_WAITOK); + vhold(dp); + nt->dp = dp; + TAILQ_INSERT_TAIL(&ndp->ni_cap_tracker, nt, nm_link); +} + +static void +nameicap_cleanup(struct nameidata *ndp) +{ + struct nameicap_tracker *nt, *nt1; + + KASSERT(TAILQ_EMPTY(&ndp->ni_cap_tracker) || + (ndp->ni_lcf & NI_LCF_CAP_DOTDOT) != 0, ("not strictrelative")); + TAILQ_FOREACH_SAFE(nt, &ndp->ni_cap_tracker, nm_link, nt1) { + TAILQ_REMOVE(&ndp->ni_cap_tracker, nt, nm_link); + vdrop(nt->dp); + uma_zfree(nt_zone, nt); + } +} + +/* + * For dotdot lookups in capability mode, only allow the component + * lookup to succeed if the resulting directory was already traversed + * during the operation. Also fail dotdot lookups for non-local + * filesystems, where external agents might assist local lookups to + * escape the compartment. + */ +static int +nameicap_check_dotdot(struct nameidata *ndp, struct vnode *dp) +{ + struct nameicap_tracker *nt; + struct mount *mp; + + if ((ndp->ni_lcf & NI_LCF_CAP_DOTDOT) == 0 || dp == NULL || + dp->v_type != VDIR) + return (0); + mp = dp->v_mount; + if (lookup_cap_dotdot_nonlocal == 0 && mp != NULL && + (mp->mnt_flag & MNT_LOCAL) == 0) + return (ENOTCAPABLE); + TAILQ_FOREACH_REVERSE(nt, &ndp->ni_cap_tracker, nameicap_tracker_head, + nm_link) { + if (dp == nt->dp) + return (0); + } + return (ENOTCAPABLE); +} + +static void +namei_cleanup_cnp(struct componentname *cnp) +{ + + uma_zfree(namei_zone, cnp->cn_pnbuf); +#ifdef DIAGNOSTIC + cnp->cn_pnbuf = NULL; + cnp->cn_nameptr = NULL; +#endif +} + +static int +namei_handle_root(struct nameidata *ndp, struct vnode **dpp) +{ + struct componentname *cnp; + + cnp = &ndp->ni_cnd; + if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) != 0) { +#ifdef KTRACE + if (KTRPOINT(curthread, KTR_CAPFAIL)) + ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL); +#endif + return (ENOTCAPABLE); + } + while (*(cnp->cn_nameptr) == '/') { + cnp->cn_nameptr++; + ndp->ni_pathlen--; + } + *dpp = ndp->ni_rootdir; + vrefact(*dpp); + return (0); +} + +/* + * Convert a pathname into a pointer to a locked vnode. + * + * The FOLLOW flag is set when symbolic links are to be followed + * when they occur at the end of the name translation process. + * Symbolic links are always followed for all other pathname + * components other than the last. + * + * The segflg defines whether the name is to be copied from user + * space or kernel space. + * + * Overall outline of namei: + * + * copy in name + * get starting directory + * while (!done && !error) { + * call lookup to search path. + * if symbolic link, massage name in buffer and continue + * } + */ +int +namei(struct nameidata *ndp) +{ + struct filedesc *fdp; /* pointer to file descriptor state */ + char *cp; /* pointer into pathname argument */ + struct vnode *dp; /* the directory we are searching */ + struct iovec aiov; /* uio for reading symbolic links */ + struct componentname *cnp; + struct file *dfp; + struct thread *td; + struct proc *p; + cap_rights_t rights; + struct uio auio; + int error, linklen, startdir_used; + + cnp = &ndp->ni_cnd; + td = cnp->cn_thread; + p = td->td_proc; + ndp->ni_cnd.cn_cred = ndp->ni_cnd.cn_thread->td_ucred; + KASSERT(cnp->cn_cred && p, ("namei: bad cred/proc")); + KASSERT((cnp->cn_nameiop & (~OPMASK)) == 0, + ("namei: nameiop contaminated with flags")); + KASSERT((cnp->cn_flags & OPMASK) == 0, + ("namei: flags contaminated with nameiops")); + MPASS(ndp->ni_startdir == NULL || ndp->ni_startdir->v_type == VDIR || + ndp->ni_startdir->v_type == VBAD); + fdp = p->p_fd; + TAILQ_INIT(&ndp->ni_cap_tracker); + ndp->ni_lcf = 0; + + /* We will set this ourselves if we need it. */ + cnp->cn_flags &= ~TRAILINGSLASH; + + /* + * Get a buffer for the name to be translated, and copy the + * name into the buffer. + */ + if ((cnp->cn_flags & HASBUF) == 0) + cnp->cn_pnbuf = uma_zalloc(namei_zone, M_WAITOK); + if (ndp->ni_segflg == UIO_SYSSPACE) + error = copystr(ndp->ni_dirp, cnp->cn_pnbuf, MAXPATHLEN, + &ndp->ni_pathlen); + else + error = copyinstr(ndp->ni_dirp, cnp->cn_pnbuf, MAXPATHLEN, + &ndp->ni_pathlen); + + /* + * Don't allow empty pathnames. + */ + if (error == 0 && *cnp->cn_pnbuf == '\0') + error = ENOENT; + +#ifdef CAPABILITY_MODE + /* + * In capability mode, lookups must be restricted to happen in + * the subtree with the root specified by the file descriptor: + * - The root must be real file descriptor, not the pseudo-descriptor + * AT_FDCWD. + * - The passed path must be relative and not absolute. + * - If lookup_cap_dotdot is disabled, path must not contain the + * '..' components. + * - If lookup_cap_dotdot is enabled, we verify that all '..' + * components lookups result in the directories which were + * previously walked by us, which prevents an escape from + * the relative root. + */ + if (error == 0 && IN_CAPABILITY_MODE(td) && + (cnp->cn_flags & NOCAPCHECK) == 0) { + ndp->ni_lcf |= NI_LCF_STRICTRELATIVE; + if (ndp->ni_dirfd == AT_FDCWD) { +#ifdef KTRACE + if (KTRPOINT(td, KTR_CAPFAIL)) + ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL); +#endif + error = ECAPMODE; + } + } +#endif + if (error != 0) { + namei_cleanup_cnp(cnp); + ndp->ni_vp = NULL; + return (error); + } + ndp->ni_loopcnt = 0; +#ifdef KTRACE + if (KTRPOINT(td, KTR_NAMEI)) { + KASSERT(cnp->cn_thread == curthread, + ("namei not using curthread")); + ktrnamei(cnp->cn_pnbuf); + } +#endif + /* + * Get starting point for the translation. + */ + FILEDESC_SLOCK(fdp); + ndp->ni_rootdir = fdp->fd_rdir; + vrefact(ndp->ni_rootdir); + ndp->ni_topdir = fdp->fd_jdir; + + /* + * If we are auditing the kernel pathname, save the user pathname. + */ + if (cnp->cn_flags & AUDITVNODE1) + AUDIT_ARG_UPATH1(td, ndp->ni_dirfd, cnp->cn_pnbuf); + if (cnp->cn_flags & AUDITVNODE2) + AUDIT_ARG_UPATH2(td, ndp->ni_dirfd, cnp->cn_pnbuf); + + startdir_used = 0; + dp = NULL; + cnp->cn_nameptr = cnp->cn_pnbuf; + if (cnp->cn_pnbuf[0] == '/') { + ndp->ni_resflags |= NIRES_ABS; + error = namei_handle_root(ndp, &dp); + } else { + if (ndp->ni_startdir != NULL) { + dp = ndp->ni_startdir; + startdir_used = 1; + } else if (ndp->ni_dirfd == AT_FDCWD) { + dp = fdp->fd_cdir; + vrefact(dp); + } else { + rights = ndp->ni_rightsneeded; + cap_rights_set(&rights, CAP_LOOKUP); + + if (cnp->cn_flags & AUDITVNODE1) + AUDIT_ARG_ATFD1(ndp->ni_dirfd); + if (cnp->cn_flags & AUDITVNODE2) + AUDIT_ARG_ATFD2(ndp->ni_dirfd); + /* + * Effectively inlined fgetvp_rights, because we need to + * inspect the file as well as grabbing the vnode. + */ + error = fget_cap_locked(fdp, ndp->ni_dirfd, &rights, + &dfp, &ndp->ni_filecaps); + if (error != 0) { + /* + * Preserve the error; it should either be EBADF + * or capability-related, both of which can be + * safely returned to the caller. + */ + } else if (dfp->f_ops == &badfileops) { + error = EBADF; + } else if (dfp->f_vnode == NULL) { + error = ENOTDIR; + } else { + dp = dfp->f_vnode; + vrefact(dp); + + if ((dfp->f_flag & FSEARCH) != 0) + cnp->cn_flags |= NOEXECCHECK; + } +#ifdef CAPABILITIES + /* + * If file descriptor doesn't have all rights, + * all lookups relative to it must also be + * strictly relative. + */ + CAP_ALL(&rights); + if (!cap_rights_contains(&ndp->ni_filecaps.fc_rights, + &rights) || + ndp->ni_filecaps.fc_fcntls != CAP_FCNTL_ALL || + ndp->ni_filecaps.fc_nioctls != -1) { + ndp->ni_lcf |= NI_LCF_STRICTRELATIVE; + } +#endif + } + if (error == 0 && dp->v_type != VDIR) + error = ENOTDIR; + } + FILEDESC_SUNLOCK(fdp); + if (ndp->ni_startdir != NULL && !startdir_used) + vrele(ndp->ni_startdir); + if (error != 0) { + if (dp != NULL) + vrele(dp); + goto out; + } + if ((ndp->ni_lcf & NI_LCF_STRICTRELATIVE) != 0 && + lookup_cap_dotdot != 0) + ndp->ni_lcf |= NI_LCF_CAP_DOTDOT; + SDT_PROBE3(vfs, namei, lookup, entry, dp, cnp->cn_pnbuf, + cnp->cn_flags); + for (;;) { + ndp->ni_startdir = dp; + error = lookup(ndp); + if (error != 0) + goto out; + /* + * If not a symbolic link, we're done. + */ + if ((cnp->cn_flags & ISSYMLINK) == 0) { + vrele(ndp->ni_rootdir); + if ((cnp->cn_flags & (SAVENAME | SAVESTART)) == 0) { + namei_cleanup_cnp(cnp); + } else + cnp->cn_flags |= HASBUF; + nameicap_cleanup(ndp); + SDT_PROBE2(vfs, namei, lookup, return, 0, ndp->ni_vp); + return (0); + } + if (ndp->ni_loopcnt++ >= MAXSYMLINKS) { + error = ELOOP; + break; + } +#ifdef MAC + if ((cnp->cn_flags & NOMACCHECK) == 0) { + error = mac_vnode_check_readlink(td->td_ucred, + ndp->ni_vp); + if (error != 0) + break; + } +#endif + if (ndp->ni_pathlen > 1) + cp = uma_zalloc(namei_zone, M_WAITOK); + else + cp = cnp->cn_pnbuf; + aiov.iov_base = cp; + aiov.iov_len = MAXPATHLEN; + auio.uio_iov = &aiov; + auio.uio_iovcnt = 1; + auio.uio_offset = 0; + auio.uio_rw = UIO_READ; + auio.uio_segflg = UIO_SYSSPACE; + auio.uio_td = td; + auio.uio_resid = MAXPATHLEN; + error = VOP_READLINK(ndp->ni_vp, &auio, cnp->cn_cred); + if (error != 0) { + if (ndp->ni_pathlen > 1) + uma_zfree(namei_zone, cp); + break; + } + linklen = MAXPATHLEN - auio.uio_resid; + if (linklen == 0) { + if (ndp->ni_pathlen > 1) + uma_zfree(namei_zone, cp); + error = ENOENT; + break; + } + if (linklen + ndp->ni_pathlen > MAXPATHLEN) { + if (ndp->ni_pathlen > 1) + uma_zfree(namei_zone, cp); + error = ENAMETOOLONG; + break; + } + if (ndp->ni_pathlen > 1) { + bcopy(ndp->ni_next, cp + linklen, ndp->ni_pathlen); + uma_zfree(namei_zone, cnp->cn_pnbuf); + cnp->cn_pnbuf = cp; + } else + cnp->cn_pnbuf[linklen] = '\0'; + ndp->ni_pathlen += linklen; + vput(ndp->ni_vp); + dp = ndp->ni_dvp; + /* + * Check if root directory should replace current directory. + */ + cnp->cn_nameptr = cnp->cn_pnbuf; + if (*(cnp->cn_nameptr) == '/') { + vrele(dp); + error = namei_handle_root(ndp, &dp); + if (error != 0) + goto out; + } + } + vput(ndp->ni_vp); + ndp->ni_vp = NULL; + vrele(ndp->ni_dvp); +out: + vrele(ndp->ni_rootdir); + namei_cleanup_cnp(cnp); + nameicap_cleanup(ndp); + SDT_PROBE2(vfs, namei, lookup, return, error, NULL); + return (error); +} + +static int +compute_cn_lkflags(struct mount *mp, int lkflags, int cnflags) +{ + + if (mp == NULL || ((lkflags & LK_SHARED) && + (!(mp->mnt_kern_flag & MNTK_LOOKUP_SHARED) || + ((cnflags & ISDOTDOT) && + (mp->mnt_kern_flag & MNTK_LOOKUP_EXCL_DOTDOT))))) { + lkflags &= ~LK_SHARED; + lkflags |= LK_EXCLUSIVE; + } + lkflags |= LK_NODDLKTREAT; + return (lkflags); +} + +static __inline int +needs_exclusive_leaf(struct mount *mp, int flags) +{ + + /* + * Intermediate nodes can use shared locks, we only need to + * force an exclusive lock for leaf nodes. + */ + if ((flags & (ISLASTCN | LOCKLEAF)) != (ISLASTCN | LOCKLEAF)) + return (0); + + /* Always use exclusive locks if LOCKSHARED isn't set. */ + if (!(flags & LOCKSHARED)) + return (1); + + /* + * For lookups during open(), if the mount point supports + * extended shared operations, then use a shared lock for the + * leaf node, otherwise use an exclusive lock. + */ + if ((flags & ISOPEN) != 0) + return (!MNT_EXTENDED_SHARED(mp)); + + /* + * Lookup requests outside of open() that specify LOCKSHARED + * only need a shared lock on the leaf vnode. + */ + return (0); +} + +/* + * Search a pathname. + * This is a very central and rather complicated routine. + * + * The pathname is pointed to by ni_ptr and is of length ni_pathlen. + * The starting directory is taken from ni_startdir. The pathname is + * descended until done, or a symbolic link is encountered. The variable + * ni_more is clear if the path is completed; it is set to one if a + * symbolic link needing interpretation is encountered. + * + * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on + * whether the name is to be looked up, created, renamed, or deleted. + * When CREATE, RENAME, or DELETE is specified, information usable in + * creating, renaming, or deleting a directory entry may be calculated. + * If flag has LOCKPARENT or'ed into it, the parent directory is returned + * locked. If flag has WANTPARENT or'ed into it, the parent directory is + * returned unlocked. Otherwise the parent directory is not returned. If + * the target of the pathname exists and LOCKLEAF is or'ed into the flag + * the target is returned locked, otherwise it is returned unlocked. + * When creating or renaming and LOCKPARENT is specified, the target may not + * be ".". When deleting and LOCKPARENT is specified, the target may be ".". + * + * Overall outline of lookup: + * + * dirloop: + * identify next component of name at ndp->ni_ptr + * handle degenerate case where name is null string + * if .. and crossing mount points and on mounted filesys, find parent + * call VOP_LOOKUP routine for next component name + * directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set + * component vnode returned in ni_vp (if it exists), locked. + * if result vnode is mounted on and crossing mount points, + * find mounted on vnode + * if more components of name, do next level at dirloop + * return the answer in ni_vp, locked if LOCKLEAF set + * if LOCKPARENT set, return locked parent in ni_dvp + * if WANTPARENT set, return unlocked parent in ni_dvp + */ +int +lookup(struct nameidata *ndp) +{ + char *cp; /* pointer into pathname argument */ + char *prev_ni_next; /* saved ndp->ni_next */ + struct vnode *dp = NULL; /* the directory we are searching */ + struct vnode *tdp; /* saved dp */ + struct mount *mp; /* mount table entry */ + struct prison *pr; + size_t prev_ni_pathlen; /* saved ndp->ni_pathlen */ + int docache; /* == 0 do not cache last component */ + int wantparent; /* 1 => wantparent or lockparent flag */ + int rdonly; /* lookup read-only flag bit */ + int error = 0; + int dpunlocked = 0; /* dp has already been unlocked */ + int relookup = 0; /* do not consume the path component */ + struct componentname *cnp = &ndp->ni_cnd; + int lkflags_save; + int ni_dvp_unlocked; + + /* + * Setup: break out flag bits into variables. + */ + ni_dvp_unlocked = 0; + wantparent = cnp->cn_flags & (LOCKPARENT | WANTPARENT); + KASSERT(cnp->cn_nameiop == LOOKUP || wantparent, + ("CREATE, DELETE, RENAME require LOCKPARENT or WANTPARENT.")); + docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE; + if (cnp->cn_nameiop == DELETE || + (wantparent && cnp->cn_nameiop != CREATE && + cnp->cn_nameiop != LOOKUP)) + docache = 0; + rdonly = cnp->cn_flags & RDONLY; + cnp->cn_flags &= ~ISSYMLINK; + ndp->ni_dvp = NULL; + /* + * We use shared locks until we hit the parent of the last cn then + * we adjust based on the requesting flags. + */ + cnp->cn_lkflags = LK_SHARED; + dp = ndp->ni_startdir; + ndp->ni_startdir = NULLVP; + vn_lock(dp, + compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags | LK_RETRY, + cnp->cn_flags)); + +dirloop: + /* + * Search a new directory. + * + * The last component of the filename is left accessible via + * cnp->cn_nameptr for callers that need the name. Callers needing + * the name set the SAVENAME flag. When done, they assume + * responsibility for freeing the pathname buffer. + */ + for (cp = cnp->cn_nameptr; *cp != 0 && *cp != '/'; cp++) + continue; + cnp->cn_namelen = cp - cnp->cn_nameptr; + if (cnp->cn_namelen > NAME_MAX) { + error = ENAMETOOLONG; + goto bad; + } +#ifdef NAMEI_DIAGNOSTIC + { char c = *cp; + *cp = '\0'; + printf("{%s}: ", cnp->cn_nameptr); + *cp = c; } +#endif + prev_ni_pathlen = ndp->ni_pathlen; + ndp->ni_pathlen -= cnp->cn_namelen; + KASSERT(ndp->ni_pathlen <= PATH_MAX, + ("%s: ni_pathlen underflow to %zd\n", __func__, ndp->ni_pathlen)); + prev_ni_next = ndp->ni_next; + ndp->ni_next = cp; + + /* + * Replace multiple slashes by a single slash and trailing slashes + * by a null. This must be done before VOP_LOOKUP() because some + * fs's don't know about trailing slashes. Remember if there were + * trailing slashes to handle symlinks, existing non-directories + * and non-existing files that won't be directories specially later. + */ + while (*cp == '/' && (cp[1] == '/' || cp[1] == '\0')) { + cp++; + ndp->ni_pathlen--; + if (*cp == '\0') { + *ndp->ni_next = '\0'; + cnp->cn_flags |= TRAILINGSLASH; + } + } + ndp->ni_next = cp; + + cnp->cn_flags |= MAKEENTRY; + if (*cp == '\0' && docache == 0) + cnp->cn_flags &= ~MAKEENTRY; + if (cnp->cn_namelen == 2 && + cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.') + cnp->cn_flags |= ISDOTDOT; + else + cnp->cn_flags &= ~ISDOTDOT; + if (*ndp->ni_next == 0) + cnp->cn_flags |= ISLASTCN; + else + cnp->cn_flags &= ~ISLASTCN; + + if ((cnp->cn_flags & ISLASTCN) != 0 && + cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.' && + (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) { + error = EINVAL; + goto bad; + } + + nameicap_tracker_add(ndp, dp); + + /* + * Check for degenerate name (e.g. / or "") + * which is a way of talking about a directory, + * e.g. like "/." or ".". + */ + if (cnp->cn_nameptr[0] == '\0') { + if (dp->v_type != VDIR) { + error = ENOTDIR; + goto bad; + } + if (cnp->cn_nameiop != LOOKUP) { + error = EISDIR; + goto bad; + } + if (wantparent) { + ndp->ni_dvp = dp; + VREF(dp); + } + ndp->ni_vp = dp; + + if (cnp->cn_flags & AUDITVNODE1) + AUDIT_ARG_VNODE1(dp); + else if (cnp->cn_flags & AUDITVNODE2) + AUDIT_ARG_VNODE2(dp); + + if (!(cnp->cn_flags & (LOCKPARENT | LOCKLEAF))) + VOP_UNLOCK(dp, 0); + /* XXX This should probably move to the top of function. */ + if (cnp->cn_flags & SAVESTART) + panic("lookup: SAVESTART"); + goto success; + } + + /* + * Handle "..": five special cases. + * 0. If doing a capability lookup and lookup_cap_dotdot is + * disabled, return ENOTCAPABLE. + * 1. Return an error if this is the last component of + * the name and the operation is DELETE or RENAME. + * 2. If at root directory (e.g. after chroot) + * or at absolute root directory + * then ignore it so can't get out. + * 3. If this vnode is the root of a mounted + * filesystem, then replace it with the + * vnode which was mounted on so we take the + * .. in the other filesystem. + * 4. If the vnode is the top directory of + * the jail or chroot, don't let them out. + * 5. If doing a capability lookup and lookup_cap_dotdot is + * enabled, return ENOTCAPABLE if the lookup would escape + * from the initial file descriptor directory. Checks are + * done by ensuring that namei() already traversed the + * result of dotdot lookup. + */ + if (cnp->cn_flags & ISDOTDOT) { + if ((ndp->ni_lcf & (NI_LCF_STRICTRELATIVE | NI_LCF_CAP_DOTDOT)) + == NI_LCF_STRICTRELATIVE) { +#ifdef KTRACE + if (KTRPOINT(curthread, KTR_CAPFAIL)) + ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL); +#endif + error = ENOTCAPABLE; + goto bad; + } + if ((cnp->cn_flags & ISLASTCN) != 0 && + (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) { + error = EINVAL; + goto bad; + } + for (;;) { + for (pr = cnp->cn_cred->cr_prison; pr != NULL; + pr = pr->pr_parent) + if (dp == pr->pr_root) + break; + if (dp == ndp->ni_rootdir || + dp == ndp->ni_topdir || + dp == rootvnode || + pr != NULL || + ((dp->v_vflag & VV_ROOT) != 0 && + (cnp->cn_flags & NOCROSSMOUNT) != 0)) { + ndp->ni_dvp = dp; + ndp->ni_vp = dp; + VREF(dp); + goto nextname; + } + if ((dp->v_vflag & VV_ROOT) == 0) + break; + if (dp->v_iflag & VI_DOOMED) { /* forced unmount */ + error = ENOENT; + goto bad; + } + tdp = dp; + dp = dp->v_mount->mnt_vnodecovered; + VREF(dp); + vput(tdp); + vn_lock(dp, + compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags | + LK_RETRY, ISDOTDOT)); + error = nameicap_check_dotdot(ndp, dp); + if (error != 0) { +#ifdef KTRACE + if (KTRPOINT(curthread, KTR_CAPFAIL)) + ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL); +#endif + goto bad; + } + } + } + + /* + * We now have a segment name to search for, and a directory to search. + */ +unionlookup: +#ifdef MAC + if ((cnp->cn_flags & NOMACCHECK) == 0) { + error = mac_vnode_check_lookup(cnp->cn_thread->td_ucred, dp, + cnp); + if (error) + goto bad; + } +#endif + ndp->ni_dvp = dp; + ndp->ni_vp = NULL; + ASSERT_VOP_LOCKED(dp, "lookup"); + /* + * If we have a shared lock we may need to upgrade the lock for the + * last operation. + */ + if ((cnp->cn_flags & LOCKPARENT) && (cnp->cn_flags & ISLASTCN) && + dp != vp_crossmp && VOP_ISLOCKED(dp) == LK_SHARED) + vn_lock(dp, LK_UPGRADE|LK_RETRY); + if ((dp->v_iflag & VI_DOOMED) != 0) { + error = ENOENT; + goto bad; + } + /* + * If we're looking up the last component and we need an exclusive + * lock, adjust our lkflags. + */ + if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags)) + cnp->cn_lkflags = LK_EXCLUSIVE; +#ifdef NAMEI_DIAGNOSTIC + vn_printf(dp, "lookup in "); +#endif + lkflags_save = cnp->cn_lkflags; + cnp->cn_lkflags = compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags, + cnp->cn_flags); + error = VOP_LOOKUP(dp, &ndp->ni_vp, cnp); + cnp->cn_lkflags = lkflags_save; + if (error != 0) { + KASSERT(ndp->ni_vp == NULL, ("leaf should be empty")); +#ifdef NAMEI_DIAGNOSTIC + printf("not found\n"); +#endif + if ((error == ENOENT) && + (dp->v_vflag & VV_ROOT) && (dp->v_mount != NULL) && + (dp->v_mount->mnt_flag & MNT_UNION)) { + tdp = dp; + dp = dp->v_mount->mnt_vnodecovered; + VREF(dp); + vput(tdp); + vn_lock(dp, + compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags | + LK_RETRY, cnp->cn_flags)); + nameicap_tracker_add(ndp, dp); + goto unionlookup; + } + + if (error == ERELOOKUP) { + vref(dp); + ndp->ni_vp = dp; + error = 0; + relookup = 1; + goto good; + } + + if (error != EJUSTRETURN) + goto bad; + /* + * At this point, we know we're at the end of the + * pathname. If creating / renaming, we can consider + * allowing the file or directory to be created / renamed, + * provided we're not on a read-only filesystem. + */ + if (rdonly) { + error = EROFS; + goto bad; + } + /* trailing slash only allowed for directories */ + if ((cnp->cn_flags & TRAILINGSLASH) && + !(cnp->cn_flags & WILLBEDIR)) { + error = ENOENT; + goto bad; + } + if ((cnp->cn_flags & LOCKPARENT) == 0) + VOP_UNLOCK(dp, 0); + /* + * We return with ni_vp NULL to indicate that the entry + * doesn't currently exist, leaving a pointer to the + * (possibly locked) directory vnode in ndp->ni_dvp. + */ + if (cnp->cn_flags & SAVESTART) { + ndp->ni_startdir = ndp->ni_dvp; + VREF(ndp->ni_startdir); + } + goto success; + } + +good: +#ifdef NAMEI_DIAGNOSTIC + printf("found\n"); +#endif + dp = ndp->ni_vp; + + /* + * Check to see if the vnode has been mounted on; + * if so find the root of the mounted filesystem. + */ + while (dp->v_type == VDIR && (mp = dp->v_mountedhere) && + (cnp->cn_flags & NOCROSSMOUNT) == 0) { + if (vfs_busy(mp, 0)) + continue; + vput(dp); + if (dp != ndp->ni_dvp) + vput(ndp->ni_dvp); + else + vrele(ndp->ni_dvp); + vrefact(vp_crossmp); + ndp->ni_dvp = vp_crossmp; + error = VFS_ROOT(mp, compute_cn_lkflags(mp, cnp->cn_lkflags, + cnp->cn_flags), &tdp); + vfs_unbusy(mp); + if (vn_lock(vp_crossmp, LK_SHARED | LK_NOWAIT)) + panic("vp_crossmp exclusively locked or reclaimed"); + if (error) { + dpunlocked = 1; + goto bad2; + } + ndp->ni_vp = dp = tdp; + } + + /* + * Check for symbolic link + */ + if ((dp->v_type == VLNK) && + ((cnp->cn_flags & FOLLOW) || (cnp->cn_flags & TRAILINGSLASH) || + *ndp->ni_next == '/')) { + cnp->cn_flags |= ISSYMLINK; + if (dp->v_iflag & VI_DOOMED) { + /* + * We can't know whether the directory was mounted with + * NOSYMFOLLOW, so we can't follow safely. + */ + error = ENOENT; + goto bad2; + } + if (dp->v_mount->mnt_flag & MNT_NOSYMFOLLOW) { + error = EACCES; + goto bad2; + } + /* + * Symlink code always expects an unlocked dvp. + */ + if (ndp->ni_dvp != ndp->ni_vp) { + VOP_UNLOCK(ndp->ni_dvp, 0); + ni_dvp_unlocked = 1; + } + goto success; + } + +nextname: + /* + * Not a symbolic link that we will follow. Continue with the + * next component if there is any; otherwise, we're done. + */ + KASSERT((cnp->cn_flags & ISLASTCN) || *ndp->ni_next == '/', + ("lookup: invalid path state.")); + if (relookup) { + relookup = 0; + ndp->ni_pathlen = prev_ni_pathlen; + ndp->ni_next = prev_ni_next; + if (ndp->ni_dvp != dp) + vput(ndp->ni_dvp); + else + vrele(ndp->ni_dvp); + goto dirloop; + } + if (cnp->cn_flags & ISDOTDOT) { + error = nameicap_check_dotdot(ndp, ndp->ni_vp); + if (error != 0) { +#ifdef KTRACE + if (KTRPOINT(curthread, KTR_CAPFAIL)) + ktrcapfail(CAPFAIL_LOOKUP, NULL, NULL); +#endif + goto bad2; + } + } + if (*ndp->ni_next == '/') { + cnp->cn_nameptr = ndp->ni_next; + while (*cnp->cn_nameptr == '/') { + cnp->cn_nameptr++; + ndp->ni_pathlen--; + } + if (ndp->ni_dvp != dp) + vput(ndp->ni_dvp); + else + vrele(ndp->ni_dvp); + goto dirloop; + } + /* + * If we're processing a path with a trailing slash, + * check that the end result is a directory. + */ + if ((cnp->cn_flags & TRAILINGSLASH) && dp->v_type != VDIR) { + error = ENOTDIR; + goto bad2; + } + /* + * Disallow directory write attempts on read-only filesystems. + */ + if (rdonly && + (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) { + error = EROFS; + goto bad2; + } + if (cnp->cn_flags & SAVESTART) { + ndp->ni_startdir = ndp->ni_dvp; + VREF(ndp->ni_startdir); + } + if (!wantparent) { + ni_dvp_unlocked = 2; + if (ndp->ni_dvp != dp) + vput(ndp->ni_dvp); + else + vrele(ndp->ni_dvp); + } else if ((cnp->cn_flags & LOCKPARENT) == 0 && ndp->ni_dvp != dp) { + VOP_UNLOCK(ndp->ni_dvp, 0); + ni_dvp_unlocked = 1; + } + + if (cnp->cn_flags & AUDITVNODE1) + AUDIT_ARG_VNODE1(dp); + else if (cnp->cn_flags & AUDITVNODE2) + AUDIT_ARG_VNODE2(dp); + + if ((cnp->cn_flags & LOCKLEAF) == 0) + VOP_UNLOCK(dp, 0); +success: + /* + * Because of shared lookup we may have the vnode shared locked, but + * the caller may want it to be exclusively locked. + */ + if (needs_exclusive_leaf(dp->v_mount, cnp->cn_flags) && + VOP_ISLOCKED(dp) != LK_EXCLUSIVE) { + vn_lock(dp, LK_UPGRADE | LK_RETRY); + if (dp->v_iflag & VI_DOOMED) { + error = ENOENT; + goto bad2; + } + } + return (0); + +bad2: + if (ni_dvp_unlocked != 2) { + if (dp != ndp->ni_dvp && !ni_dvp_unlocked) + vput(ndp->ni_dvp); + else + vrele(ndp->ni_dvp); + } +bad: + if (!dpunlocked) + vput(dp); + ndp->ni_vp = NULL; + return (error); +} + +/* + * relookup - lookup a path name component + * Used by lookup to re-acquire things. + */ +int +relookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp) +{ + struct vnode *dp = NULL; /* the directory we are searching */ + int wantparent; /* 1 => wantparent or lockparent flag */ + int rdonly; /* lookup read-only flag bit */ + int error = 0; + + KASSERT(cnp->cn_flags & ISLASTCN, + ("relookup: Not given last component.")); + /* + * Setup: break out flag bits into variables. + */ + wantparent = cnp->cn_flags & (LOCKPARENT|WANTPARENT); + KASSERT(wantparent, ("relookup: parent not wanted.")); + rdonly = cnp->cn_flags & RDONLY; + cnp->cn_flags &= ~ISSYMLINK; + dp = dvp; + cnp->cn_lkflags = LK_EXCLUSIVE; + vn_lock(dp, LK_EXCLUSIVE | LK_RETRY); + + /* + * Search a new directory. + * + * The last component of the filename is left accessible via + * cnp->cn_nameptr for callers that need the name. Callers needing + * the name set the SAVENAME flag. When done, they assume + * responsibility for freeing the pathname buffer. + */ +#ifdef NAMEI_DIAGNOSTIC + printf("{%s}: ", cnp->cn_nameptr); +#endif + + /* + * Check for "" which represents the root directory after slash + * removal. + */ + if (cnp->cn_nameptr[0] == '\0') { + /* + * Support only LOOKUP for "/" because lookup() + * can't succeed for CREATE, DELETE and RENAME. + */ + KASSERT(cnp->cn_nameiop == LOOKUP, ("nameiop must be LOOKUP")); + KASSERT(dp->v_type == VDIR, ("dp is not a directory")); + + if (!(cnp->cn_flags & LOCKLEAF)) + VOP_UNLOCK(dp, 0); + *vpp = dp; + /* XXX This should probably move to the top of function. */ + if (cnp->cn_flags & SAVESTART) + panic("lookup: SAVESTART"); + return (0); + } + + if (cnp->cn_flags & ISDOTDOT) + panic ("relookup: lookup on dot-dot"); + + /* + * We now have a segment name to search for, and a directory to search. + */ +#ifdef NAMEI_DIAGNOSTIC + vn_printf(dp, "search in "); +#endif + if ((error = VOP_LOOKUP(dp, vpp, cnp)) != 0) { + KASSERT(*vpp == NULL, ("leaf should be empty")); + if (error != EJUSTRETURN) + goto bad; + /* + * If creating and at end of pathname, then can consider + * allowing file to be created. + */ + if (rdonly) { + error = EROFS; + goto bad; + } + /* ASSERT(dvp == ndp->ni_startdir) */ + if (cnp->cn_flags & SAVESTART) + VREF(dvp); + if ((cnp->cn_flags & LOCKPARENT) == 0) + VOP_UNLOCK(dp, 0); + /* + * We return with ni_vp NULL to indicate that the entry + * doesn't currently exist, leaving a pointer to the + * (possibly locked) directory vnode in ndp->ni_dvp. + */ + return (0); + } + + dp = *vpp; + + /* + * Disallow directory write attempts on read-only filesystems. + */ + if (rdonly && + (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) { + if (dvp == dp) + vrele(dvp); + else + vput(dvp); + error = EROFS; + goto bad; + } + /* + * Set the parent lock/ref state to the requested state. + */ + if ((cnp->cn_flags & LOCKPARENT) == 0 && dvp != dp) { + if (wantparent) + VOP_UNLOCK(dvp, 0); + else + vput(dvp); + } else if (!wantparent) + vrele(dvp); + /* + * Check for symbolic link + */ + KASSERT(dp->v_type != VLNK || !(cnp->cn_flags & FOLLOW), + ("relookup: symlink found.\n")); + + /* ASSERT(dvp == ndp->ni_startdir) */ + if (cnp->cn_flags & SAVESTART) + VREF(dvp); + + if ((cnp->cn_flags & LOCKLEAF) == 0) + VOP_UNLOCK(dp, 0); + return (0); +bad: + vput(dp); + *vpp = NULL; + return (error); +} + +void +NDINIT_ALL(struct nameidata *ndp, u_long op, u_long flags, enum uio_seg segflg, + const char *namep, int dirfd, struct vnode *startdir, cap_rights_t *rightsp, + struct thread *td) +{ + + ndp->ni_cnd.cn_nameiop = op; + ndp->ni_cnd.cn_flags = flags; + ndp->ni_segflg = segflg; + ndp->ni_dirp = namep; + ndp->ni_dirfd = dirfd; + ndp->ni_startdir = startdir; + ndp->ni_resflags = 0; + if (rightsp != NULL) + ndp->ni_rightsneeded = *rightsp; + else + cap_rights_init(&ndp->ni_rightsneeded); + filecaps_init(&ndp->ni_filecaps); + ndp->ni_cnd.cn_thread = td; +} + +/* + * Free data allocated by namei(); see namei(9) for details. + */ +void +NDFREE(struct nameidata *ndp, const u_int flags) +{ + int unlock_dvp; + int unlock_vp; + + unlock_dvp = 0; + unlock_vp = 0; + + if (!(flags & NDF_NO_FREE_PNBUF) && + (ndp->ni_cnd.cn_flags & HASBUF)) { + uma_zfree(namei_zone, ndp->ni_cnd.cn_pnbuf); + ndp->ni_cnd.cn_flags &= ~HASBUF; + } + if (!(flags & NDF_NO_VP_UNLOCK) && + (ndp->ni_cnd.cn_flags & LOCKLEAF) && ndp->ni_vp) + unlock_vp = 1; + if (!(flags & NDF_NO_DVP_UNLOCK) && + (ndp->ni_cnd.cn_flags & LOCKPARENT) && + ndp->ni_dvp != ndp->ni_vp) + unlock_dvp = 1; + if (!(flags & NDF_NO_VP_RELE) && ndp->ni_vp) { + if (unlock_vp) { + vput(ndp->ni_vp); + unlock_vp = 0; + } else + vrele(ndp->ni_vp); + ndp->ni_vp = NULL; + } + if (unlock_vp) + VOP_UNLOCK(ndp->ni_vp, 0); + if (!(flags & NDF_NO_DVP_RELE) && + (ndp->ni_cnd.cn_flags & (LOCKPARENT|WANTPARENT))) { + if (unlock_dvp) { + vput(ndp->ni_dvp); + unlock_dvp = 0; + } else + vrele(ndp->ni_dvp); + ndp->ni_dvp = NULL; + } + if (unlock_dvp) + VOP_UNLOCK(ndp->ni_dvp, 0); + if (!(flags & NDF_NO_STARTDIR_RELE) && + (ndp->ni_cnd.cn_flags & SAVESTART)) { + vrele(ndp->ni_startdir); + ndp->ni_startdir = NULL; + } +} + +/* + * Determine if there is a suitable alternate filename under the specified + * prefix for the specified path. If the create flag is set, then the + * alternate prefix will be used so long as the parent directory exists. + * This is used by the various compatibility ABIs so that Linux binaries prefer + * files under /compat/linux for example. The chosen path (whether under + * the prefix or under /) is returned in a kernel malloc'd buffer pointed + * to by pathbuf. The caller is responsible for free'ing the buffer from + * the M_TEMP bucket if one is returned. + */ +int +kern_alternate_path(struct thread *td, const char *prefix, const char *path, + enum uio_seg pathseg, char **pathbuf, int create, int dirfd) +{ + struct nameidata nd, ndroot; + char *ptr, *buf, *cp; + size_t len, sz; + int error; + + buf = (char *) malloc(MAXPATHLEN, M_TEMP, M_WAITOK); + *pathbuf = buf; + + /* Copy the prefix into the new pathname as a starting point. */ + len = strlcpy(buf, prefix, MAXPATHLEN); + if (len >= MAXPATHLEN) { + *pathbuf = NULL; + free(buf, M_TEMP); + return (EINVAL); + } + sz = MAXPATHLEN - len; + ptr = buf + len; + + /* Append the filename to the prefix. */ + if (pathseg == UIO_SYSSPACE) + error = copystr(path, ptr, sz, &len); + else + error = copyinstr(path, ptr, sz, &len); + + if (error) { + *pathbuf = NULL; + free(buf, M_TEMP); + return (error); + } + + /* Only use a prefix with absolute pathnames. */ + if (*ptr != '/') { + error = EINVAL; + goto keeporig; + } + + if (dirfd != AT_FDCWD) { + /* + * We want the original because the "prefix" is + * included in the already opened dirfd. + */ + bcopy(ptr, buf, len); + return (0); + } + + /* + * We know that there is a / somewhere in this pathname. + * Search backwards for it, to find the file's parent dir + * to see if it exists in the alternate tree. If it does, + * and we want to create a file (cflag is set). We don't + * need to worry about the root comparison in this case. + */ + + if (create) { + for (cp = &ptr[len] - 1; *cp != '/'; cp--); + *cp = '\0'; + + NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, buf, td); + error = namei(&nd); + *cp = '/'; + if (error != 0) + goto keeporig; + } else { + NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, buf, td); + + error = namei(&nd); + if (error != 0) + goto keeporig; + + /* + * We now compare the vnode of the prefix to the one + * vnode asked. If they resolve to be the same, then we + * ignore the match so that the real root gets used. + * This avoids the problem of traversing "../.." to find the + * root directory and never finding it, because "/" resolves + * to the emulation root directory. This is expensive :-( + */ + NDINIT(&ndroot, LOOKUP, FOLLOW, UIO_SYSSPACE, prefix, + td); + + /* We shouldn't ever get an error from this namei(). */ + error = namei(&ndroot); + if (error == 0) { + if (nd.ni_vp == ndroot.ni_vp) + error = ENOENT; + + NDFREE(&ndroot, NDF_ONLY_PNBUF); + vrele(ndroot.ni_vp); + } + } + + NDFREE(&nd, NDF_ONLY_PNBUF); + vrele(nd.ni_vp); + +keeporig: + /* If there was an error, use the original path name. */ + if (error) + bcopy(ptr, buf, len); + return (error); +} |