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NetBSD/sys/kern/vfs_lookup.c

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/* $NetBSD: vfs_lookup.c,v 1.234 2023/05/01 05:12:44 mlelstv Exp $ */
/*
* 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 8.10 (Berkeley) 5/27/95
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: vfs_lookup.c,v 1.234 2023/05/01 05:12:44 mlelstv Exp $");
#ifdef _KERNEL_OPT
#include "opt_magiclinks.h"
#endif
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/syslimits.h>
#include <sys/time.h>
#include <sys/namei.h>
#include <sys/vnode.h>
#include <sys/vnode_impl.h>
#include <sys/fstrans.h>
#include <sys/mount.h>
#include <sys/errno.h>
#include <sys/filedesc.h>
#include <sys/hash.h>
#include <sys/proc.h>
#include <sys/syslog.h>
#include <sys/kauth.h>
#include <sys/ktrace.h>
#include <sys/dirent.h>
#ifndef MAGICLINKS
#define MAGICLINKS 0
#endif
int vfs_magiclinks = MAGICLINKS;
__CTASSERT(MAXNAMLEN == NAME_MAX);
/*
* Substitute replacement text for 'magic' strings in symlinks.
* Returns 0 if successful, and returns non-zero if an error
* occurs. (Currently, the only possible error is running out
* of temporary pathname space.)
*
* Looks for "@<string>" and "@<string>/", where <string> is a
* recognized 'magic' string. Replaces the "@<string>" with the
* appropriate replacement text. (Note that in some cases the
* replacement text may have zero length.)
*
* This would have been table driven, but the variance in
* replacement strings (and replacement string lengths) made
* that impractical.
*/
#define VNL(x) \
(sizeof(x) - 1)
#define VO '{'
#define VC '}'
#define MATCH(str) \
((termchar == '/' && i + VNL(str) == *len) || \
(i + VNL(str) < *len && \
cp[i + VNL(str)] == termchar)) && \
!strncmp((str), &cp[i], VNL(str))
#define SUBSTITUTE(m, s, sl) \
if ((newlen + (sl)) >= MAXPATHLEN) \
return 1; \
i += VNL(m); \
if (termchar != '/') \
i++; \
(void)memcpy(&tmp[newlen], (s), (sl)); \
newlen += (sl); \
change = 1; \
termchar = '/';
static int
symlink_magic(struct proc *p, char *cp, size_t *len)
{
char *tmp;
size_t change, i, newlen, slen;
char termchar = '/';
char idtmp[11]; /* enough for 32 bit *unsigned* integer */
tmp = PNBUF_GET();
for (change = i = newlen = 0; i < *len; ) {
if (cp[i] != '@') {
tmp[newlen++] = cp[i++];
continue;
}
i++;
/* Check for @{var} syntax. */
if (cp[i] == VO) {
termchar = VC;
i++;
}
/*
* The following checks should be ordered according
* to frequency of use.
*/
if (MATCH("machine_arch")) {
slen = strlen(PROC_MACHINE_ARCH(p));
SUBSTITUTE("machine_arch", PROC_MACHINE_ARCH(p), slen);
} else if (MATCH("machine")) {
slen = VNL(MACHINE);
SUBSTITUTE("machine", MACHINE, slen);
} else if (MATCH("hostname")) {
SUBSTITUTE("hostname", hostname, hostnamelen);
} else if (MATCH("osrelease")) {
slen = strlen(osrelease);
SUBSTITUTE("osrelease", osrelease, slen);
} else if (MATCH("emul")) {
slen = strlen(p->p_emul->e_name);
SUBSTITUTE("emul", p->p_emul->e_name, slen);
} else if (MATCH("kernel_ident")) {
slen = strlen(kernel_ident);
SUBSTITUTE("kernel_ident", kernel_ident, slen);
} else if (MATCH("domainname")) {
SUBSTITUTE("domainname", domainname, domainnamelen);
} else if (MATCH("ostype")) {
slen = strlen(ostype);
SUBSTITUTE("ostype", ostype, slen);
} else if (MATCH("uid")) {
slen = snprintf(idtmp, sizeof(idtmp), "%u",
kauth_cred_geteuid(kauth_cred_get()));
SUBSTITUTE("uid", idtmp, slen);
} else if (MATCH("ruid")) {
slen = snprintf(idtmp, sizeof(idtmp), "%u",
kauth_cred_getuid(kauth_cred_get()));
SUBSTITUTE("ruid", idtmp, slen);
} else if (MATCH("gid")) {
slen = snprintf(idtmp, sizeof(idtmp), "%u",
kauth_cred_getegid(kauth_cred_get()));
SUBSTITUTE("gid", idtmp, slen);
} else if (MATCH("rgid")) {
slen = snprintf(idtmp, sizeof(idtmp), "%u",
kauth_cred_getgid(kauth_cred_get()));
SUBSTITUTE("rgid", idtmp, slen);
} else {
tmp[newlen++] = '@';
if (termchar == VC)
tmp[newlen++] = VO;
}
}
if (change) {
(void)memcpy(cp, tmp, newlen);
*len = newlen;
}
PNBUF_PUT(tmp);
return 0;
}
#undef VNL
#undef VO
#undef VC
#undef MATCH
#undef SUBSTITUTE
////////////////////////////////////////////////////////////
/*
* Determine the namei hash (for the namecache) for name.
* If *ep != NULL, hash from name to ep-1.
* If *ep == NULL, hash from name until the first NUL or '/', and
* return the location of this termination character in *ep.
*
* This function returns an equivalent hash to the MI hash32_strn().
* The latter isn't used because in the *ep == NULL case, determining
* the length of the string to the first NUL or `/' and then calling
* hash32_strn() involves unnecessary double-handling of the data.
*/
uint32_t
namei_hash(const char *name, const char **ep)
{
uint32_t hash;
hash = HASH32_STR_INIT;
if (*ep != NULL) {
for (; name < *ep; name++)
hash = hash * 33 + *(const uint8_t *)name;
} else {
for (; *name != '\0' && *name != '/'; name++)
hash = hash * 33 + *(const uint8_t *)name;
*ep = name;
}
return (hash + (hash >> 5));
}
////////////////////////////////////////////////////////////
/*
* Sealed abstraction for pathnames.
*
* System-call-layer level code that is going to call namei should
* first create a pathbuf and adjust all the bells and whistles on it
* as needed by context.
*/
struct pathbuf {
char *pb_path;
char *pb_pathcopy;
unsigned pb_pathcopyuses;
};
static struct pathbuf *
pathbuf_create_raw(void)
{
struct pathbuf *pb;
pb = kmem_alloc(sizeof(*pb), KM_SLEEP);
pb->pb_path = PNBUF_GET();
if (pb->pb_path == NULL) {
kmem_free(pb, sizeof(*pb));
return NULL;
}
pb->pb_pathcopy = NULL;
pb->pb_pathcopyuses = 0;
return pb;
}
void
pathbuf_destroy(struct pathbuf *pb)
{
KASSERT(pb->pb_pathcopyuses == 0);
KASSERT(pb->pb_pathcopy == NULL);
PNBUF_PUT(pb->pb_path);
kmem_free(pb, sizeof(*pb));
}
struct pathbuf *
pathbuf_assimilate(char *pnbuf)
{
struct pathbuf *pb;
pb = kmem_alloc(sizeof(*pb), KM_SLEEP);
pb->pb_path = pnbuf;
pb->pb_pathcopy = NULL;
pb->pb_pathcopyuses = 0;
return pb;
}
struct pathbuf *
pathbuf_create(const char *path)
{
struct pathbuf *pb;
int error;
pb = pathbuf_create_raw();
if (pb == NULL) {
return NULL;
}
error = copystr(path, pb->pb_path, PATH_MAX, NULL);
if (error != 0) {
KASSERT(!"kernel path too long in pathbuf_create");
/* make sure it's null-terminated, just in case */
pb->pb_path[PATH_MAX-1] = '\0';
}
return pb;
}
int
pathbuf_copyin(const char *userpath, struct pathbuf **ret)
{
struct pathbuf *pb;
int error;
pb = pathbuf_create_raw();
if (pb == NULL) {
return ENOMEM;
}
error = copyinstr(userpath, pb->pb_path, PATH_MAX, NULL);
if (error) {
pathbuf_destroy(pb);
return error;
}
*ret = pb;
return 0;
}
/*
* XXX should not exist:
* 1. whether a pointer is kernel or user should be statically checkable.
* 2. copyin should be handled by the upper part of the syscall layer,
* not in here.
*/
int
pathbuf_maybe_copyin(const char *path, enum uio_seg seg, struct pathbuf **ret)
{
if (seg == UIO_USERSPACE) {
return pathbuf_copyin(path, ret);
} else {
*ret = pathbuf_create(path);
if (*ret == NULL) {
return ENOMEM;
}
return 0;
}
}
/*
* Get a copy of the path buffer as it currently exists. If this is
* called after namei starts the results may be arbitrary.
*/
void
pathbuf_copystring(const struct pathbuf *pb, char *buf, size_t maxlen)
{
strlcpy(buf, pb->pb_path, maxlen);
}
/*
* These two functions allow access to a saved copy of the original
* path string. The first copy should be gotten before namei is
* called. Each copy that is gotten should be put back.
*/
const char *
pathbuf_stringcopy_get(struct pathbuf *pb)
{
if (pb->pb_pathcopyuses == 0) {
pb->pb_pathcopy = PNBUF_GET();
strcpy(pb->pb_pathcopy, pb->pb_path);
}
pb->pb_pathcopyuses++;
return pb->pb_pathcopy;
}
void
pathbuf_stringcopy_put(struct pathbuf *pb, const char *str)
{
KASSERT(str == pb->pb_pathcopy);
KASSERT(pb->pb_pathcopyuses > 0);
pb->pb_pathcopyuses--;
if (pb->pb_pathcopyuses == 0) {
PNBUF_PUT(pb->pb_pathcopy);
pb->pb_pathcopy = NULL;
}
}
////////////////////////////////////////////////////////////
/*
* namei: convert a pathname into a pointer to a (maybe-locked) vnode,
* and maybe also its parent directory vnode, and assorted other guff.
* See namei(9) for the interface documentation.
*
*
* 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
* }
*/
/*
* 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 passed in. 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. 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, locked.
* 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
*/
/*
* Internal state for a namei operation.
*
* cnp is always equal to &ndp->ni_cnp.
*/
struct namei_state {
struct nameidata *ndp;
struct componentname *cnp;
int docache; /* == 0 do not cache last component */
int rdonly; /* lookup read-only flag bit */
int slashes;
unsigned attempt_retry:1; /* true if error allows emul retry */
unsigned root_referenced:1; /* true if ndp->ni_rootdir and
ndp->ni_erootdir were referenced */
};
/*
* Initialize the namei working state.
*/
static void
namei_init(struct namei_state *state, struct nameidata *ndp)
{
state->ndp = ndp;
state->cnp = &ndp->ni_cnd;
state->docache = 0;
state->rdonly = 0;
state->slashes = 0;
state->root_referenced = 0;
KASSERTMSG((state->cnp->cn_cred != NULL), "namei: bad cred/proc");
KASSERTMSG(((state->cnp->cn_nameiop & (~OPMASK)) == 0),
"namei: nameiop contaminated with flags: %08"PRIx32,
state->cnp->cn_nameiop);
KASSERTMSG(((state->cnp->cn_flags & OPMASK) == 0),
"name: flags contaminated with nameiops: %08"PRIx32,
state->cnp->cn_flags);
/*
* The buffer for name translation shall be the one inside the
* pathbuf.
*/
state->ndp->ni_pnbuf = state->ndp->ni_pathbuf->pb_path;
}
/*
* Clean up the working namei state, leaving things ready for return
* from namei.
*/
static void
namei_cleanup(struct namei_state *state)
{
KASSERT(state->cnp == &state->ndp->ni_cnd);
if (state->root_referenced) {
if (state->ndp->ni_rootdir != NULL)
vrele(state->ndp->ni_rootdir);
if (state->ndp->ni_erootdir != NULL)
vrele(state->ndp->ni_erootdir);
}
}
//////////////////////////////
/*
* Get the directory context.
* Initializes the rootdir and erootdir state and returns a reference
* to the starting dir.
*/
static struct vnode *
namei_getstartdir(struct namei_state *state)
{
struct nameidata *ndp = state->ndp;
struct componentname *cnp = state->cnp;
struct cwdinfo *cwdi; /* pointer to cwd state */
struct lwp *self = curlwp; /* thread doing namei() */
struct vnode *rootdir, *erootdir, *curdir, *startdir;
if (state->root_referenced) {
if (state->ndp->ni_rootdir != NULL)
vrele(state->ndp->ni_rootdir);
if (state->ndp->ni_erootdir != NULL)
vrele(state->ndp->ni_erootdir);
state->root_referenced = 0;
}
cwdi = self->l_proc->p_cwdi;
rw_enter(&cwdi->cwdi_lock, RW_READER);
/* root dir */
if (cwdi->cwdi_rdir == NULL || (cnp->cn_flags & NOCHROOT)) {
rootdir = rootvnode;
} else {
rootdir = cwdi->cwdi_rdir;
}
/* emulation root dir, if any */
if ((cnp->cn_flags & TRYEMULROOT) == 0) {
/* if we don't want it, don't fetch it */
erootdir = NULL;
} else if (cnp->cn_flags & EMULROOTSET) {
/* explicitly set emulroot; "/../" doesn't override this */
erootdir = ndp->ni_erootdir;
} else if (!strncmp(ndp->ni_pnbuf, "/../", 4)) {
/* explicit reference to real rootdir */
erootdir = NULL;
} else {
/* may be null */
erootdir = cwdi->cwdi_edir;
}
/* current dir */
curdir = cwdi->cwdi_cdir;
if (ndp->ni_pnbuf[0] != '/') {
if (ndp->ni_atdir != NULL) {
startdir = ndp->ni_atdir;
} else {
startdir = curdir;
}
erootdir = NULL;
} else if (cnp->cn_flags & TRYEMULROOT && erootdir != NULL) {
startdir = erootdir;
} else {
startdir = rootdir;
erootdir = NULL;
}
state->ndp->ni_rootdir = rootdir;
state->ndp->ni_erootdir = erootdir;
/*
* Get a reference to the start dir so we can safely unlock cwdi.
*
* Must hold references to rootdir and erootdir while we're running.
* A multithreaded process may chroot during namei.
*/
if (startdir != NULL)
vref(startdir);
if (state->ndp->ni_rootdir != NULL)
vref(state->ndp->ni_rootdir);
if (state->ndp->ni_erootdir != NULL)
vref(state->ndp->ni_erootdir);
state->root_referenced = 1;
rw_exit(&cwdi->cwdi_lock);
return startdir;
}
/*
* Get the directory context for the nfsd case, in parallel to
* getstartdir. Initializes the rootdir and erootdir state and
* returns a reference to the passed-in starting dir.
*/
static struct vnode *
namei_getstartdir_for_nfsd(struct namei_state *state)
{
KASSERT(state->ndp->ni_atdir != NULL);
/* always use the real root, and never set an emulation root */
if (rootvnode == NULL) {
return NULL;
}
state->ndp->ni_rootdir = rootvnode;
state->ndp->ni_erootdir = NULL;
vref(state->ndp->ni_atdir);
KASSERT(! state->root_referenced);
vref(state->ndp->ni_rootdir);
state->root_referenced = 1;
return state->ndp->ni_atdir;
}
/*
* Ktrace the namei operation.
*/
static void
namei_ktrace(struct namei_state *state)
{
struct nameidata *ndp = state->ndp;
struct componentname *cnp = state->cnp;
struct lwp *self = curlwp; /* thread doing namei() */
const char *emul_path;
if (ktrpoint(KTR_NAMEI)) {
if (ndp->ni_erootdir != NULL) {
/*
* To make any sense, the trace entry need to have the
* text of the emulation path prepended.
* Usually we can get this from the current process,
* but when called from emul_find_interp() it is only
* in the exec_package - so we get it passed in ni_next
* (this is a hack).
*/
if (cnp->cn_flags & EMULROOTSET)
emul_path = ndp->ni_next;
else
emul_path = self->l_proc->p_emul->e_path;
ktrnamei2(emul_path, strlen(emul_path),
ndp->ni_pnbuf, ndp->ni_pathlen);
} else
ktrnamei(ndp->ni_pnbuf, ndp->ni_pathlen);
}
}
/*
* Start up namei. Find the root dir and cwd, establish the starting
* directory for lookup, and lock it. Also calls ktrace when
* appropriate.
*/
static int
namei_start(struct namei_state *state, int isnfsd,
struct vnode **startdir_ret)
{
struct nameidata *ndp = state->ndp;
struct vnode *startdir;
/* length includes null terminator (was originally from copyinstr) */
ndp->ni_pathlen = strlen(ndp->ni_pnbuf) + 1;
/*
* POSIX.1 requirement: "" is not a valid file name.
*/
if (ndp->ni_pathlen == 1) {
ndp->ni_erootdir = NULL;
return ENOENT;
}
ndp->ni_loopcnt = 0;
/* Get starting directory, set up root, and ktrace. */
if (isnfsd) {
startdir = namei_getstartdir_for_nfsd(state);
/* no ktrace */
} else {
startdir = namei_getstartdir(state);
namei_ktrace(state);
}
if (startdir == NULL) {
return ENOENT;
}
/* NDAT may feed us with a non directory namei_getstartdir */
if (startdir->v_type != VDIR) {
vrele(startdir);
return ENOTDIR;
}
*startdir_ret = startdir;
return 0;
}
/*
* Check for being at a symlink that we're going to follow.
*/
static inline int
namei_atsymlink(struct namei_state *state, struct vnode *foundobj)
{
return (foundobj->v_type == VLNK) &&
(state->cnp->cn_flags & (FOLLOW|REQUIREDIR));
}
/*
* Follow a symlink.
*
* Updates searchdir. inhibitmagic causes magic symlinks to not be
* interpreted; this is used by nfsd.
*
* Unlocks foundobj on success (ugh)
*/
static inline int
namei_follow(struct namei_state *state, int inhibitmagic,
struct vnode *searchdir, struct vnode *foundobj,
struct vnode **newsearchdir_ret)
{
struct nameidata *ndp = state->ndp;
struct componentname *cnp = state->cnp;
struct lwp *self = curlwp; /* thread doing namei() */
struct iovec aiov; /* uio for reading symbolic links */
struct uio auio;
char *cp; /* pointer into pathname argument */
size_t linklen;
int error;
if (ndp->ni_loopcnt++ >= MAXSYMLINKS) {
return ELOOP;
}
vn_lock(foundobj, LK_EXCLUSIVE | LK_RETRY);
if (foundobj->v_mount->mnt_flag & MNT_SYMPERM) {
error = VOP_ACCESS(foundobj, VEXEC, cnp->cn_cred);
if (error != 0) {
VOP_UNLOCK(foundobj);
return error;
}
}
/* FUTURE: fix this to not use a second buffer */
cp = PNBUF_GET();
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_resid = MAXPATHLEN;
UIO_SETUP_SYSSPACE(&auio);
error = VOP_READLINK(foundobj, &auio, cnp->cn_cred);
VOP_UNLOCK(foundobj);
if (error) {
PNBUF_PUT(cp);
return error;
}
linklen = MAXPATHLEN - auio.uio_resid;
if (linklen == 0) {
PNBUF_PUT(cp);
return ENOENT;
}
/*
* Do symlink substitution, if appropriate, and
* check length for potential overflow.
*
* Inhibit symlink substitution for nfsd.
* XXX: This is how it was before; is that a bug or a feature?
*/
if ((!inhibitmagic && vfs_magiclinks &&
symlink_magic(self->l_proc, cp, &linklen)) ||
(linklen + ndp->ni_pathlen >= MAXPATHLEN)) {
PNBUF_PUT(cp);
return ENAMETOOLONG;
}
if (ndp->ni_pathlen > 1) {
/* includes a null-terminator */
memcpy(cp + linklen, ndp->ni_next, ndp->ni_pathlen);
} else {
cp[linklen] = '\0';
}
ndp->ni_pathlen += linklen;
memcpy(ndp->ni_pnbuf, cp, ndp->ni_pathlen);
PNBUF_PUT(cp);
/* we're now starting from the beginning of the buffer again */
cnp->cn_nameptr = ndp->ni_pnbuf;
/*
* Check if root directory should replace current directory.
*/
if (ndp->ni_pnbuf[0] == '/') {
vrele(searchdir);
/* Keep absolute symbolic links inside emulation root */
searchdir = ndp->ni_erootdir;
if (searchdir == NULL ||
(ndp->ni_pnbuf[1] == '.'
&& ndp->ni_pnbuf[2] == '.'
&& ndp->ni_pnbuf[3] == '/')) {
ndp->ni_erootdir = NULL;
searchdir = ndp->ni_rootdir;
}
vref(searchdir);
while (cnp->cn_nameptr[0] == '/') {
cnp->cn_nameptr++;
ndp->ni_pathlen--;
}
}
*newsearchdir_ret = searchdir;
return 0;
}
//////////////////////////////
/*
* Inspect the leading path component and update the state accordingly.
*/
static int
lookup_parsepath(struct namei_state *state, struct vnode *searchdir)
{
const char *cp; /* pointer into pathname argument */
int error;
struct componentname *cnp = state->cnp;
struct nameidata *ndp = state->ndp;
KASSERT(cnp == &ndp->ni_cnd);
/*
* 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.
*
* At this point, our only vnode state is that the search dir
* is held.
*/
error = VOP_PARSEPATH(searchdir, cnp->cn_nameptr, &cnp->cn_namelen);
if (error) {
return error;
}
cp = cnp->cn_nameptr + cnp->cn_namelen;
if (cnp->cn_namelen > KERNEL_NAME_MAX) {
return ENAMETOOLONG;
}
#ifdef NAMEI_DIAGNOSTIC
{ char c = *cp;
*(char *)cp = '\0';
printf("{%s}: ", cnp->cn_nameptr);
*(char *)cp = c; }
#endif /* NAMEI_DIAGNOSTIC */
ndp->ni_pathlen -= cnp->cn_namelen;
ndp->ni_next = cp;
/*
* If this component is followed by a slash, then move the pointer to
* the next component forward, and remember that this component must be
* a directory.
*/
if (*cp == '/') {
do {
cp++;
} while (*cp == '/');
state->slashes = cp - ndp->ni_next;
ndp->ni_pathlen -= state->slashes;
ndp->ni_next = cp;
cnp->cn_flags |= REQUIREDIR;
} else {
state->slashes = 0;
cnp->cn_flags &= ~REQUIREDIR;
}
/*
* We do special processing on the last component, whether or not it's
* a directory. Cache all intervening lookups, but not the final one.
*/
if (*cp == '\0') {
if (state->docache)
cnp->cn_flags |= MAKEENTRY;
else
cnp->cn_flags &= ~MAKEENTRY;
cnp->cn_flags |= ISLASTCN;
} else {
cnp->cn_flags |= MAKEENTRY;
cnp->cn_flags &= ~ISLASTCN;
}
if (cnp->cn_namelen == 2 &&
cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.')
cnp->cn_flags |= ISDOTDOT;
else
cnp->cn_flags &= ~ISDOTDOT;
return 0;
}
/*
* Take care of crossing a mounted-on vnode. On error, foundobj_ret will be
* vrele'd, but searchdir is left alone.
*/
static int
lookup_crossmount(struct namei_state *state,
struct vnode **searchdir_ret,
struct vnode **foundobj_ret,
bool *searchdir_locked)
{
struct componentname *cnp = state->cnp;
struct vnode *foundobj, *vp;
struct vnode *searchdir;
struct mount *mp;
int error, lktype;
searchdir = *searchdir_ret;
foundobj = *foundobj_ret;
error = 0;
KASSERT((cnp->cn_flags & NOCROSSMOUNT) == 0);
/* First, unlock searchdir (oof). */
if (*searchdir_locked) {
KASSERT(searchdir != NULL);
lktype = VOP_ISLOCKED(searchdir);
VOP_UNLOCK(searchdir);
*searchdir_locked = false;
} else {
lktype = LK_NONE;
}
/*
* Do an unlocked check to see if the vnode has been mounted on; if
* so find the root of the mounted file system.
*/
while (foundobj->v_type == VDIR &&
(mp = foundobj->v_mountedhere) != NULL &&
(cnp->cn_flags & NOCROSSMOUNT) == 0) {
/*
* Try the namecache first. If that doesn't work, do
* it the hard way.
*/
if (cache_lookup_mount(foundobj, &vp)) {
vrele(foundobj);
foundobj = vp;
} else {
/* First get the vnodes mount stable. */
while ((mp = foundobj->v_mountedhere) != NULL) {
fstrans_start(mp);
if (fstrans_held(mp) &&
mp == foundobj->v_mountedhere) {
break;
}
fstrans_done(mp);
}
if (mp == NULL) {
break;
}
/*
* Now get a reference on the root vnode.
* XXX Future - maybe allow only VDIR here.
*/
error = VFS_ROOT(mp, LK_NONE, &vp);
/*
* If successful, enter it into the cache while
* holding the mount busy (competing with unmount).
*/
if (error == 0) {
cache_enter_mount(foundobj, vp);
}
/* Finally, drop references to foundobj & mountpoint. */
vrele(foundobj);
fstrans_done(mp);
if (error) {
foundobj = NULL;
break;
}
foundobj = vp;
}
/*
* Avoid locking vnodes from two filesystems because
* it's prone to deadlock, e.g. when using puffs.
* Also, it isn't a good idea to propagate slowness of
* a filesystem up to the root directory. For now,
* only handle the common case, where foundobj is
* VDIR.
*
* In this case set searchdir to null to avoid using
* it again. It is not correct to set searchdir ==
* foundobj here as that will confuse the caller.
* (See PR 40740.)
*/
if (searchdir == NULL) {
/* already been here once; do nothing further */
} else if (foundobj->v_type == VDIR) {
vrele(searchdir);
*searchdir_ret = searchdir = NULL;
lktype = LK_NONE;
}
}
/* If searchdir is still around, re-lock it. */
if (error == 0 && lktype != LK_NONE) {
vn_lock(searchdir, lktype | LK_RETRY);
*searchdir_locked = true;
}
*foundobj_ret = foundobj;
return error;
}
/*
* Determine the desired locking mode for the directory of a lookup.
*/
static int
lookup_lktype(struct vnode *searchdir, struct componentname *cnp)
{
/*
* If the file system supports VOP_LOOKUP() with a shared lock, and
* we are not making any modifications (nameiop LOOKUP) or this is
* not the last component then get a shared lock. Where we can't do
* fast-forwarded lookups (for example with layered file systems)
* then this is the fallback for reducing lock contention.
*/
if ((searchdir->v_mount->mnt_iflag & IMNT_SHRLOOKUP) != 0 &&
(cnp->cn_nameiop == LOOKUP || (cnp->cn_flags & ISLASTCN) == 0)) {
return LK_SHARED;
} else {
return LK_EXCLUSIVE;
}
}
/*
* Call VOP_LOOKUP for a single lookup; return a new search directory
* (used when crossing mountpoints up or searching union mounts down) and
* the found object, which for create operations may be NULL on success.
*
* Note that the new search directory may be null, which means the
* searchdir was unlocked and released. This happens in the common case
* when crossing a mount point downwards, in order to avoid coupling
* locks between different file system volumes. Importantly, this can
* happen even if the call fails. (XXX: this is gross and should be
* tidied somehow.)
*/
static int
lookup_once(struct namei_state *state,
struct vnode *searchdir,
struct vnode **newsearchdir_ret,
struct vnode **foundobj_ret,
bool *newsearchdir_locked_ret)
{
struct vnode *tmpvn; /* scratch vnode */
struct vnode *foundobj; /* result */
struct lwp *l = curlwp;
bool searchdir_locked = false;
int error, lktype;
struct componentname *cnp = state->cnp;
struct nameidata *ndp = state->ndp;
KASSERT(cnp == &ndp->ni_cnd);
*newsearchdir_ret = searchdir;
/*
* Handle "..": two special cases.
* 1. If at root directory (e.g. after chroot)
* or at absolute root directory
* then ignore it so can't get out.
* 1a. If at the root of the emulation filesystem go to the real
* root. So "/../<path>" is always absolute.
* 1b. If we have somehow gotten out of a jail, warn
* and also ignore it so we can't get farther out.
* 2. 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 file system.
*/
if (cnp->cn_flags & ISDOTDOT) {
struct proc *p = l->l_proc;
for (;;) {
if (searchdir == ndp->ni_rootdir ||
searchdir == rootvnode) {
foundobj = searchdir;
vref(foundobj);
*foundobj_ret = foundobj;
if (cnp->cn_flags & LOCKPARENT) {
lktype = lookup_lktype(searchdir, cnp);
vn_lock(searchdir, lktype | LK_RETRY);
searchdir_locked = true;
}
error = 0;
goto done;
}
if (ndp->ni_rootdir != rootvnode) {
int retval;
retval = vn_isunder(searchdir, ndp->ni_rootdir, l);
if (!retval) {
/* Oops! We got out of jail! */
log(LOG_WARNING,
"chrooted pid %d uid %d (%s) "
"detected outside of its chroot\n",
p->p_pid, kauth_cred_geteuid(l->l_cred),
p->p_comm);
/* Put us at the jail root. */
vrele(searchdir);
searchdir = NULL;
foundobj = ndp->ni_rootdir;
vref(foundobj);
vref(foundobj);
*newsearchdir_ret = foundobj;
*foundobj_ret = foundobj;
error = 0;
goto done;
}
}
if ((searchdir->v_vflag & VV_ROOT) == 0 ||
(cnp->cn_flags & NOCROSSMOUNT))
break;
tmpvn = searchdir;
searchdir = searchdir->v_mount->mnt_vnodecovered;
vref(searchdir);
vrele(tmpvn);
*newsearchdir_ret = searchdir;
}
}
lktype = lookup_lktype(searchdir, cnp);
/*
* We now have a segment name to search for, and a directory to search.
* Our vnode state here is that "searchdir" is held.
*/
unionlookup:
foundobj = NULL;
if (!searchdir_locked) {
vn_lock(searchdir, lktype | LK_RETRY);
searchdir_locked = true;
}
error = VOP_LOOKUP(searchdir, &foundobj, cnp);
if (error != 0) {
KASSERTMSG((foundobj == NULL),
"leaf `%s' should be empty but is %p",
cnp->cn_nameptr, foundobj);
#ifdef NAMEI_DIAGNOSTIC
printf("not found\n");
#endif /* NAMEI_DIAGNOSTIC */
/*
* If ENOLCK, the file system needs us to retry the lookup
* with an exclusive lock. It's likely nothing was found in
* cache and/or modifications need to be made.
*/
if (error == ENOLCK) {
KASSERT(VOP_ISLOCKED(searchdir) == LK_SHARED);
KASSERT(searchdir_locked);
if (vn_lock(searchdir, LK_UPGRADE | LK_NOWAIT)) {
VOP_UNLOCK(searchdir);
searchdir_locked = false;
}
lktype = LK_EXCLUSIVE;
goto unionlookup;
}
if ((error == ENOENT) &&
(searchdir->v_vflag & VV_ROOT) &&
(searchdir->v_mount->mnt_flag & MNT_UNION)) {
tmpvn = searchdir;
searchdir = searchdir->v_mount->mnt_vnodecovered;
vref(searchdir);
vput(tmpvn);
searchdir_locked = false;
*newsearchdir_ret = searchdir;
goto unionlookup;
}
if (error != EJUSTRETURN)
goto done;
/*
* If this was not the last component, or there were trailing
* slashes, and we are not going to create a directory,
* then the name must exist.
*/
if ((cnp->cn_flags & (REQUIREDIR | CREATEDIR)) == REQUIREDIR) {
error = ENOENT;
goto done;
}
/*
* If creating and at end of pathname, then can consider
* allowing file to be created.
*/
if (state->rdonly) {
error = EROFS;
goto done;
}
/*
* We return success and a NULL foundobj to indicate
* that the entry doesn't currently exist, leaving a
* pointer to the (normally, locked) directory vnode
* as searchdir.
*/
*foundobj_ret = NULL;
error = 0;
goto done;
}
#ifdef NAMEI_DIAGNOSTIC
printf("found\n");
#endif /* NAMEI_DIAGNOSTIC */
/* Unlock, unless the caller needs the parent locked. */
if (searchdir != NULL) {
KASSERT(searchdir_locked);
if ((cnp->cn_flags & (ISLASTCN | LOCKPARENT)) !=
(ISLASTCN | LOCKPARENT)) {
VOP_UNLOCK(searchdir);
searchdir_locked = false;
}
} else {
KASSERT(!searchdir_locked);
}
*foundobj_ret = foundobj;
error = 0;
done:
*newsearchdir_locked_ret = searchdir_locked;
return error;
}
/*
* Parse out the first path name component that we need to to consider.
*
* While doing this, attempt to use the name cache to fast-forward through
* as many "easy" to find components of the path as possible.
*
* We use the namecache's node locks to form a chain, and avoid as many
* vnode references and locks as possible. In the ideal case, only the
* final vnode will have its reference count adjusted and lock taken.
*/
static int
lookup_fastforward(struct namei_state *state, struct vnode **searchdir_ret,
struct vnode **foundobj_ret)
{
struct componentname *cnp = state->cnp;
struct nameidata *ndp = state->ndp;
krwlock_t *plock;
struct vnode *foundobj, *searchdir;
int error, error2;
size_t oldpathlen;
const char *oldnameptr;
bool terminal;
/*
* Eat as many path name components as possible before giving up and
* letting lookup_once() handle it. Remember the starting point in
* case we can't get vnode references and need to roll back.
*/
plock = NULL;
searchdir = *searchdir_ret;
oldnameptr = cnp->cn_nameptr;
oldpathlen = ndp->ni_pathlen;
terminal = false;
for (;;) {
foundobj = NULL;
/*
* Get the next component name. There should be no slashes
* here, and we shouldn't have looped around if we were
* done.
*/
KASSERT(cnp->cn_nameptr[0] != '/');
KASSERT(cnp->cn_nameptr[0] != '\0');
if ((error = lookup_parsepath(state, searchdir)) != 0) {
break;
}
/*
* Can't deal with DOTDOT lookups if NOCROSSMOUNT or the
* lookup is chrooted.
*/
if ((cnp->cn_flags & ISDOTDOT) != 0) {
if ((searchdir->v_vflag & VV_ROOT) != 0 &&
(cnp->cn_flags & NOCROSSMOUNT)) {
error = EOPNOTSUPP;
break;
}
if (ndp->ni_rootdir != rootvnode) {
error = EOPNOTSUPP;
break;
}
}
/*
* Can't deal with last component when modifying; this needs
* searchdir locked and VOP_LOOKUP() called (which can and
* does modify state, despite the name). NB: this case means
* terminal is never set true when LOCKPARENT.
*/
if ((cnp->cn_flags & ISLASTCN) != 0) {
if (cnp->cn_nameiop != LOOKUP ||
(cnp->cn_flags & LOCKPARENT) != 0) {
error = EOPNOTSUPP;
break;
}
}
/*
* Good, now look for it in cache. cache_lookup_linked()
* will fail if there's nothing there, or if there's no
* ownership info for the directory, or if the user doesn't
* have permission to look up files in this directory.
*/
if (!cache_lookup_linked(searchdir, cnp->cn_nameptr,
cnp->cn_namelen, &foundobj, &plock, cnp->cn_cred)) {
error = EOPNOTSUPP;
break;
}
KASSERT(plock != NULL);
KASSERT(rw_lock_held(plock));
/*
* Scored a hit. Negative is good too (ENOENT). If there's
* a '-o union' mount here, punt and let lookup_once() deal
* with it.
*/
if (foundobj == NULL) {
if ((searchdir->v_vflag & VV_ROOT) != 0 &&
(searchdir->v_mount->mnt_flag & MNT_UNION) != 0) {
error = EOPNOTSUPP;
} else {
error = ENOENT;
terminal = ((cnp->cn_flags & ISLASTCN) != 0);
}
break;
}
/*
* Stop and get a hold on the vnode if we've encountered
* something other than a dirctory.
*/
if (foundobj->v_type != VDIR) {
error = vcache_tryvget(foundobj);
if (error != 0) {
foundobj = NULL;
error = EOPNOTSUPP;
} else {
terminal = (foundobj->v_type != VLNK &&
(cnp->cn_flags & ISLASTCN) != 0);
}
break;
}
/*
* Try to cross mountpoints, bearing in mind that they can
* be stacked. If at any point we can't go further, stop
* and try to get a reference on the vnode. If we are able
* to get a ref then lookup_crossmount() will take care of
* it, otherwise we'll fall through to lookup_once().
*/
if (foundobj->v_mountedhere != NULL) {
while (foundobj->v_mountedhere != NULL &&
(cnp->cn_flags & NOCROSSMOUNT) == 0 &&
cache_cross_mount(&foundobj, &plock)) {
KASSERT(foundobj != NULL);
KASSERT(foundobj->v_type == VDIR);
}
if (foundobj->v_mountedhere != NULL) {
error = vcache_tryvget(foundobj);
if (error != 0) {
foundobj = NULL;
error = EOPNOTSUPP;
}
break;
} else {
searchdir = NULL;
}
}
/*
* Time to stop if we found the last component & traversed
* all mounts.
*/
if ((cnp->cn_flags & ISLASTCN) != 0) {
error = vcache_tryvget(foundobj);
if (error != 0) {
foundobj = NULL;
error = EOPNOTSUPP;
} else {
terminal = (foundobj->v_type != VLNK);
}
break;
}
/*
* Otherwise, we're still in business. Set the found VDIR
* vnode as the search dir for the next component and
* continue on to it.
*/
cnp->cn_nameptr = ndp->ni_next;
searchdir = foundobj;
}
if (terminal) {
/*
* If we exited the loop above having successfully located
* the last component with a zero error code, and it's not a
* symbolic link, then the parent directory is not needed.
* Release reference to the starting parent and make the
* terminal parent disappear into thin air.
*/
KASSERT(plock != NULL);
rw_exit(plock);
vrele(*searchdir_ret);
*searchdir_ret = NULL;
} else if (searchdir != *searchdir_ret) {
/*
* Otherwise we need to return the parent. If we ended up
* with a new search dir, ref it before dropping the
* namecache's lock. The lock prevents both searchdir and
* foundobj from disappearing. If we can't ref the new
* searchdir, we have a bit of a problem. Roll back the
* fastforward to the beginning and let lookup_once() take
* care of it.
*/
if (searchdir == NULL) {
/*
* It's possible for searchdir to be NULL in the
* case of a root vnode being reclaimed while
* trying to cross a mount.
*/
error2 = EOPNOTSUPP;
} else {
error2 = vcache_tryvget(searchdir);
}
KASSERT(plock != NULL);
rw_exit(plock);
if (__predict_true(error2 == 0)) {
/* Returning new searchdir, and maybe new foundobj. */
vrele(*searchdir_ret);
*searchdir_ret = searchdir;
} else {
/* Returning nothing. */
if (foundobj != NULL) {
vrele(foundobj);
foundobj = NULL;
}
cnp->cn_nameptr = oldnameptr;
ndp->ni_pathlen = oldpathlen;
error = lookup_parsepath(state, *searchdir_ret);
if (error == 0) {
error = EOPNOTSUPP;
}
}
} else if (plock != NULL) {
/* Drop any namecache lock still held. */
rw_exit(plock);
}
KASSERT(error == 0 ? foundobj != NULL : foundobj == NULL);
*foundobj_ret = foundobj;
return error;
}
//////////////////////////////
/*
* Do a complete path search from a single root directory.
* (This is called up to twice if TRYEMULROOT is in effect.)
*/
static int
namei_oneroot(struct namei_state *state,
int neverfollow, int inhibitmagic, int isnfsd)
{
struct nameidata *ndp = state->ndp;
struct componentname *cnp = state->cnp;
struct vnode *searchdir, *foundobj;
bool searchdir_locked = false;
int error;
error = namei_start(state, isnfsd, &searchdir);
if (error) {
ndp->ni_dvp = NULL;
ndp->ni_vp = NULL;
return error;
}
KASSERT(searchdir->v_type == VDIR);
/*
* Setup: break out flag bits into variables.
*/
state->docache = (cnp->cn_flags & NOCACHE) ^ NOCACHE;
if (cnp->cn_nameiop == DELETE)
state->docache = 0;
state->rdonly = cnp->cn_flags & RDONLY;
/*
* Keep going until we run out of path components.
*/
cnp->cn_nameptr = ndp->ni_pnbuf;
/* drop leading slashes (already used them to choose startdir) */
while (cnp->cn_nameptr[0] == '/') {
cnp->cn_nameptr++;
ndp->ni_pathlen--;
}
/* was it just "/"? */
if (cnp->cn_nameptr[0] == '\0') {
foundobj = searchdir;
searchdir = NULL;
cnp->cn_flags |= ISLASTCN;
/* bleh */
goto skiploop;
}
for (;;) {
KASSERT(searchdir != NULL);
KASSERT(!searchdir_locked);
/*
* Parse out the first path name component that we need to
* to consider. While doing this, attempt to use the name
* cache to fast-forward through as many "easy" to find
* components of the path as possible.
*/
error = lookup_fastforward(state, &searchdir, &foundobj);
/*
* If we didn't get a good answer from the namecache, then
* go directly to the file system.
*/
if (error == EOPNOTSUPP) {
error = lookup_once(state, searchdir, &searchdir,
&foundobj, &searchdir_locked);
}
/*
* If the vnode we found is mounted on, then cross the mount
* and get the root vnode in foundobj. If this encounters
* an error, it will dispose of foundobj, but searchdir is
* untouched.
*/
if (error == 0 && foundobj != NULL &&
foundobj->v_type == VDIR &&
foundobj->v_mountedhere != NULL &&
(cnp->cn_flags & NOCROSSMOUNT) == 0) {
error = lookup_crossmount(state, &searchdir,
&foundobj, &searchdir_locked);
}
if (error) {
if (searchdir != NULL) {
if (searchdir_locked) {
searchdir_locked = false;
vput(searchdir);
} else {
vrele(searchdir);
}
}
ndp->ni_dvp = NULL;
ndp->ni_vp = NULL;
/*
* Note that if we're doing TRYEMULROOT we can
* retry with the normal root. Where this is
* currently set matches previous practice,
* but the previous practice didn't make much
* sense and somebody should sit down and
* figure out which cases should cause retry
* and which shouldn't. XXX.
*/
state->attempt_retry = 1;
return (error);
}
if (foundobj == NULL) {
/*
* Success with no object returned means we're
* creating something and it isn't already
* there. Break out of the main loop now so
* the code below doesn't have to test for
* foundobj == NULL.
*/
/* lookup_once can't have dropped the searchdir */
KASSERT(searchdir != NULL ||
(cnp->cn_flags & ISLASTCN) != 0);
break;
}
/*
* Check for symbolic link. If we've reached one,
* follow it, unless we aren't supposed to. Back up
* over any slashes that we skipped, as we will need
* them again.
*/
if (namei_atsymlink(state, foundobj)) {
/* Don't need searchdir locked any more. */
if (searchdir_locked) {
searchdir_locked = false;
VOP_UNLOCK(searchdir);
}
ndp->ni_pathlen += state->slashes;
ndp->ni_next -= state->slashes;
if (neverfollow) {
error = EINVAL;
} else if (searchdir == NULL) {
/*
* dholland 20160410: lookup_once only
* drops searchdir if it crossed a
* mount point. Therefore, if we get
* here it means we crossed a mount
* point to a mounted filesystem whose
* root vnode is a symlink. In theory
* we could continue at this point by
* using the pre-crossing searchdir
* (e.g. just take out an extra
* reference on it before calling
* lookup_once so we still have it),
* but this will make an ugly mess and
* it should never happen in practice
* as only badly broken filesystems
* have non-directory root vnodes. (I
* have seen this sort of thing with
* NFS occasionally but even then it
* means something's badly wrong.)
*/
error = ENOTDIR;
} else {
/*
* dholland 20110410: if we're at a
* union mount it might make sense to
* use the top of the union stack here
* rather than the layer we found the
* symlink in. (FUTURE)
*/
error = namei_follow(state, inhibitmagic,
searchdir, foundobj,
&searchdir);
}
if (error) {
KASSERT(searchdir != foundobj);
if (searchdir != NULL) {
vrele(searchdir);
}
vrele(foundobj);
ndp->ni_dvp = NULL;
ndp->ni_vp = NULL;
return error;
}
vrele(foundobj);
foundobj = NULL;
/*
* If we followed a symlink to `/' and there
* are no more components after the symlink,
* we're done with the loop and what we found
* is the searchdir.
*/
if (cnp->cn_nameptr[0] == '\0') {
KASSERT(searchdir != NULL);
foundobj = searchdir;
searchdir = NULL;
cnp->cn_flags |= ISLASTCN;
break;
}
continue;
}
/*
* Not a symbolic link.
*
* Check for directory, if the component was
* followed by a series of slashes.
*/
if ((foundobj->v_type != VDIR) &&
(cnp->cn_flags & REQUIREDIR)) {
KASSERT(foundobj != searchdir);
if (searchdir) {
if (searchdir_locked) {
searchdir_locked = false;
vput(searchdir);
} else {
vrele(searchdir);
}
} else {
KASSERT(!searchdir_locked);
}
vrele(foundobj);
ndp->ni_dvp = NULL;
ndp->ni_vp = NULL;
state->attempt_retry = 1;
return ENOTDIR;
}
/*
* Stop if we've reached the last component.
*/
if (cnp->cn_flags & ISLASTCN) {
break;
}
/*
* Continue with the next component.
*/
cnp->cn_nameptr = ndp->ni_next;
if (searchdir != NULL) {
if (searchdir_locked) {
searchdir_locked = false;
vput(searchdir);
} else {
vrele(searchdir);
}
}
searchdir = foundobj;
foundobj = NULL;
}
KASSERT((cnp->cn_flags & LOCKPARENT) == 0 || searchdir == NULL ||
VOP_ISLOCKED(searchdir) == LK_EXCLUSIVE);
skiploop:
if (foundobj != NULL) {
if (foundobj == ndp->ni_erootdir) {
/*
* We are about to return the emulation root.
* This isn't a good idea because code might
* repeatedly lookup ".." until the file
* matches that returned for "/" and loop
* forever. So convert it to the real root.
*/
if (searchdir != NULL) {
if (searchdir_locked) {
vput(searchdir);
searchdir_locked = false;
} else {
vrele(searchdir);
}
searchdir = NULL;
}
vrele(foundobj);
foundobj = ndp->ni_rootdir;
vref(foundobj);
}
/*
* If the caller requested the parent node (i.e. it's
* a CREATE, DELETE, or RENAME), and we don't have one
* (because this is the root directory, or we crossed
* a mount point), then we must fail.
*
* 20210604 dholland when NONEXCLHACK is set (open
* with O_CREAT but not O_EXCL) skip this logic. Since
* we have a foundobj, open will not be creating, so
* it doesn't actually need or use the searchdir, so
* it's ok to return it even if it's on a different
* volume, and it's also ok to return NULL; by setting
* NONEXCLHACK the open code promises to cope with
* those cases correctly. (That is, it should do what
* it would do anyway, that is, just release the
* searchdir, except not crash if it's null.) This is
* needed because otherwise opening mountpoints with
* O_CREAT but not O_EXCL fails... which is a silly
* thing to do but ought to work. (This whole issue
* came to light because 3rd party code wanted to open
* certain procfs nodes with O_CREAT for some 3rd
* party reason, and it failed.)
*
* Note that NONEXCLHACK is properly a different
* nameiop (it is partway between LOOKUP and CREATE)
* but it was stuffed in as a flag instead to make the
* resulting patch less invasive for pullup. Blah.
*/
if (cnp->cn_nameiop != LOOKUP &&
(searchdir == NULL ||
searchdir->v_mount != foundobj->v_mount) &&
(cnp->cn_flags & NONEXCLHACK) == 0) {
if (searchdir) {
if (searchdir_locked) {
vput(searchdir);
searchdir_locked = false;
} else {
vrele(searchdir);
}
searchdir = NULL;
}
vrele(foundobj);
foundobj = NULL;
ndp->ni_dvp = NULL;
ndp->ni_vp = NULL;
state->attempt_retry = 1;
switch (cnp->cn_nameiop) {
case CREATE:
return EEXIST;
case DELETE:
case RENAME:
return EBUSY;
default:
break;
}
panic("Invalid nameiop\n");
}
/*
* Disallow directory write attempts on read-only lookups.
* Prefers EEXIST over EROFS for the CREATE case.
*/
if (state->rdonly &&
(cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
if (searchdir) {
if (searchdir_locked) {
vput(searchdir);
searchdir_locked = false;
} else {
vrele(searchdir);
}
searchdir = NULL;
}
vrele(foundobj);
foundobj = NULL;
ndp->ni_dvp = NULL;
ndp->ni_vp = NULL;
state->attempt_retry = 1;
return EROFS;
}
/* Lock the leaf node if requested. */
if ((cnp->cn_flags & (LOCKLEAF | LOCKPARENT)) == LOCKPARENT &&
searchdir == foundobj) {
/*
* Note: if LOCKPARENT but not LOCKLEAF is
* set, and searchdir == foundobj, this code
* necessarily unlocks the parent as well as
* the leaf. That is, just because you specify
* LOCKPARENT doesn't mean you necessarily get
* a locked parent vnode. The code in
* vfs_syscalls.c, and possibly elsewhere,
* that uses this combination "knows" this, so
* it can't be safely changed. Feh. XXX
*/
KASSERT(searchdir_locked);
VOP_UNLOCK(searchdir);
searchdir_locked = false;
} else if ((cnp->cn_flags & LOCKLEAF) != 0 &&
(searchdir != foundobj ||
(cnp->cn_flags & LOCKPARENT) == 0)) {
const int lktype = (cnp->cn_flags & LOCKSHARED) != 0 ?
LK_SHARED : LK_EXCLUSIVE;
vn_lock(foundobj, lktype | LK_RETRY);
}
}
/*
* Done.
*/
/*
* If LOCKPARENT is not set, the parent directory isn't returned.
*/
if ((cnp->cn_flags & LOCKPARENT) == 0 && searchdir != NULL) {
vrele(searchdir);
searchdir = NULL;
}
ndp->ni_dvp = searchdir;
ndp->ni_vp = foundobj;
return 0;
}
/*
* Do namei; wrapper layer that handles TRYEMULROOT.
*/
static int
namei_tryemulroot(struct namei_state *state,
int neverfollow, int inhibitmagic, int isnfsd)
{
int error;
struct nameidata *ndp = state->ndp;
struct componentname *cnp = state->cnp;
const char *savepath = NULL;
KASSERT(cnp == &ndp->ni_cnd);
if (cnp->cn_flags & TRYEMULROOT) {
savepath = pathbuf_stringcopy_get(ndp->ni_pathbuf);
}
emul_retry:
state->attempt_retry = 0;
error = namei_oneroot(state, neverfollow, inhibitmagic, isnfsd);
if (error) {
/*
* Once namei has started up, the existence of ni_erootdir
* tells us whether we're working from an emulation root.
* The TRYEMULROOT flag isn't necessarily authoritative.
*/
if (ndp->ni_erootdir != NULL && state->attempt_retry) {
/* Retry the whole thing using the normal root */
cnp->cn_flags &= ~TRYEMULROOT;
state->attempt_retry = 0;
/* kinda gross */
strcpy(ndp->ni_pathbuf->pb_path, savepath);
pathbuf_stringcopy_put(ndp->ni_pathbuf, savepath);
savepath = NULL;
goto emul_retry;
}
}
if (savepath != NULL) {
pathbuf_stringcopy_put(ndp->ni_pathbuf, savepath);
}
return error;
}
/*
* External interface.
*/
int
namei(struct nameidata *ndp)
{
struct namei_state state;
int error;
namei_init(&state, ndp);
error = namei_tryemulroot(&state,
0/*!neverfollow*/, 0/*!inhibitmagic*/,
0/*isnfsd*/);
namei_cleanup(&state);
if (error) {
/* make sure no stray refs leak out */
KASSERT(ndp->ni_dvp == NULL);
KASSERT(ndp->ni_vp == NULL);
}
return error;
}
////////////////////////////////////////////////////////////
/*
* External interface used by nfsd. This is basically different from
* namei only in that it has the ability to pass in the "current
* directory", and uses an extra flag "neverfollow" for which there's
* no physical flag defined in namei.h. (There used to be a cut&paste
* copy of about half of namei in nfsd to allow these minor
* adjustments to exist.)
*
* XXX: the namei interface should be adjusted so nfsd can just use
* ordinary namei().
*/
int
lookup_for_nfsd(struct nameidata *ndp, struct vnode *forcecwd, int neverfollow)
{
struct namei_state state;
int error;
KASSERT(ndp->ni_atdir == NULL);
ndp->ni_atdir = forcecwd;
namei_init(&state, ndp);
error = namei_tryemulroot(&state,
neverfollow, 1/*inhibitmagic*/, 1/*isnfsd*/);
namei_cleanup(&state);
if (error) {
/* make sure no stray refs leak out */
KASSERT(ndp->ni_dvp == NULL);
KASSERT(ndp->ni_vp == NULL);
}
return error;
}
/*
* A second external interface used by nfsd. This turns out to be a
* single lookup used by the WebNFS code (ha!) to get "index.html" or
* equivalent when asked for a directory. It should eventually evolve
* into some kind of namei_once() call; for the time being it's kind
* of a mess. XXX.
*
* dholland 20110109: I don't think it works, and I don't think it
* worked before I started hacking and slashing either, and I doubt
* anyone will ever notice.
*/
/*
* Internals. This calls lookup_once() after setting up the assorted
* pieces of state the way they ought to be.
*/
static int
do_lookup_for_nfsd_index(struct namei_state *state)
{
int error;
struct componentname *cnp = state->cnp;
struct nameidata *ndp = state->ndp;
struct vnode *startdir;
struct vnode *foundobj;
bool startdir_locked;
const char *cp; /* pointer into pathname argument */
KASSERT(cnp == &ndp->ni_cnd);
startdir = state->ndp->ni_atdir;
cnp->cn_nameptr = ndp->ni_pnbuf;
state->docache = 1;
state->rdonly = cnp->cn_flags & RDONLY;
ndp->ni_dvp = NULL;
error = VOP_PARSEPATH(startdir, cnp->cn_nameptr, &cnp->cn_namelen);
if (error) {
return error;
}
cp = cnp->cn_nameptr + cnp->cn_namelen;
KASSERT(cnp->cn_namelen <= KERNEL_NAME_MAX);
ndp->ni_pathlen -= cnp->cn_namelen;
ndp->ni_next = cp;
state->slashes = 0;
cnp->cn_flags &= ~REQUIREDIR;
cnp->cn_flags |= MAKEENTRY|ISLASTCN;
if (cnp->cn_namelen == 2 &&
cnp->cn_nameptr[1] == '.' && cnp->cn_nameptr[0] == '.')
cnp->cn_flags |= ISDOTDOT;
else
cnp->cn_flags &= ~ISDOTDOT;
/*
* Because lookup_once can change the startdir, we need our
* own reference to it to avoid consuming the caller's.
*/
vref(startdir);
error = lookup_once(state, startdir, &startdir, &foundobj,
&startdir_locked);
KASSERT((cnp->cn_flags & LOCKPARENT) == 0);
if (startdir_locked) {
VOP_UNLOCK(startdir);
startdir_locked = false;
}
/*
* If the vnode we found is mounted on, then cross the mount and get
* the root vnode in foundobj. If this encounters an error, it will
* dispose of foundobj, but searchdir is untouched.
*/
if (error == 0 && foundobj != NULL &&
foundobj->v_type == VDIR &&
foundobj->v_mountedhere != NULL &&
(cnp->cn_flags & NOCROSSMOUNT) == 0) {
error = lookup_crossmount(state, &startdir, &foundobj,
&startdir_locked);
}
/* Now toss startdir and see if we have an error. */
if (startdir != NULL)
vrele(startdir);
if (error)
foundobj = NULL;
else if (foundobj != NULL && (cnp->cn_flags & LOCKLEAF) != 0)
vn_lock(foundobj, LK_EXCLUSIVE | LK_RETRY);
ndp->ni_vp = foundobj;
return (error);
}
/*
* External interface. The partitioning between this function and the
* above isn't very clear - the above function exists mostly so code
* that uses "state->" can be shuffled around without having to change
* it to "state.".
*/
int
lookup_for_nfsd_index(struct nameidata *ndp, struct vnode *startdir)
{
struct namei_state state;
int error;
KASSERT(ndp->ni_atdir == NULL);
ndp->ni_atdir = startdir;
/*
* Note: the name sent in here (is not|should not be) allowed
* to contain a slash.
*/
if (strlen(ndp->ni_pathbuf->pb_path) > KERNEL_NAME_MAX) {
return ENAMETOOLONG;
}
if (strchr(ndp->ni_pathbuf->pb_path, '/')) {
return EINVAL;
}
ndp->ni_pathlen = strlen(ndp->ni_pathbuf->pb_path) + 1;
ndp->ni_pnbuf = NULL;
ndp->ni_cnd.cn_nameptr = NULL;
namei_init(&state, ndp);
error = do_lookup_for_nfsd_index(&state);
namei_cleanup(&state);
return error;
}
////////////////////////////////////////////////////////////
/*
* Reacquire a path name component.
* dvp is locked on entry and exit.
* *vpp is locked on exit unless it's NULL.
*/
int
relookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp, int dummy)
{
int rdonly; /* lookup read-only flag bit */
int error = 0;
#ifdef DEBUG
size_t newlen; /* DEBUG: check name len */
const char *cp; /* DEBUG: check name ptr */
#endif /* DEBUG */
(void)dummy;
/*
* Setup: break out flag bits into variables.
*/
rdonly = cnp->cn_flags & RDONLY;
/*
* Search a new directory.
*
* The cn_hash value is for use by vfs_cache.
* 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 DEBUG
#if 0
cp = NULL;
newhash = namei_hash(cnp->cn_nameptr, &cp);
if ((uint32_t)newhash != (uint32_t)cnp->cn_hash)
panic("relookup: bad hash");
#endif
error = VOP_PARSEPATH(dvp, cnp->cn_nameptr, &newlen);
if (error) {
panic("relookup: parsepath failed with error %d", error);
}
if (cnp->cn_namelen != newlen)
panic("relookup: bad len");
cp = cnp->cn_nameptr + cnp->cn_namelen;
while (*cp == '/')
cp++;
if (*cp != 0)
panic("relookup: not last component");
#endif /* DEBUG */
/*
* 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')
panic("relookup: null name");
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.
*/
*vpp = NULL;
error = VOP_LOOKUP(dvp, vpp, cnp);
if ((error) != 0) {
KASSERTMSG((*vpp == NULL),
"leaf `%s' should be empty but is %p",
cnp->cn_nameptr, *vpp);
if (error != EJUSTRETURN)
goto bad;
}
/*
* Check for symbolic link
*/
KASSERTMSG((*vpp == NULL || (*vpp)->v_type != VLNK ||
(cnp->cn_flags & FOLLOW) == 0),
"relookup: symlink found");
/*
* Check for read-only lookups.
*/
if (rdonly && cnp->cn_nameiop != LOOKUP) {
error = EROFS;
if (*vpp) {
vrele(*vpp);
}
goto bad;
}
/*
* Lock result.
*/
if (*vpp && *vpp != dvp) {
error = vn_lock(*vpp, LK_EXCLUSIVE);
if (error != 0) {
vrele(*vpp);
goto bad;
}
}
return (0);
bad:
*vpp = NULL;
return (error);
}
/*
* namei_simple - simple forms of namei.
*
* These are wrappers to allow the simple case callers of namei to be
* left alone while everything else changes under them.
*/
/* Flags */
struct namei_simple_flags_type {
int dummy;
};
static const struct namei_simple_flags_type ns_nn, ns_nt, ns_fn, ns_ft;
const namei_simple_flags_t NSM_NOFOLLOW_NOEMULROOT = &ns_nn;
const namei_simple_flags_t NSM_NOFOLLOW_TRYEMULROOT = &ns_nt;
const namei_simple_flags_t NSM_FOLLOW_NOEMULROOT = &ns_fn;
const namei_simple_flags_t NSM_FOLLOW_TRYEMULROOT = &ns_ft;
static
int
namei_simple_convert_flags(namei_simple_flags_t sflags)
{
if (sflags == NSM_NOFOLLOW_NOEMULROOT)
return NOFOLLOW | 0;
if (sflags == NSM_NOFOLLOW_TRYEMULROOT)
return NOFOLLOW | TRYEMULROOT;
if (sflags == NSM_FOLLOW_NOEMULROOT)
return FOLLOW | 0;
if (sflags == NSM_FOLLOW_TRYEMULROOT)
return FOLLOW | TRYEMULROOT;
panic("namei_simple_convert_flags: bogus sflags\n");
return 0;
}
int
namei_simple_kernel(const char *path, namei_simple_flags_t sflags,
struct vnode **vp_ret)
{
return nameiat_simple_kernel(NULL, path, sflags, vp_ret);
}
int
nameiat_simple_kernel(struct vnode *dvp, const char *path,
namei_simple_flags_t sflags, struct vnode **vp_ret)
{
struct nameidata nd;
struct pathbuf *pb;
int err;
pb = pathbuf_create(path);
if (pb == NULL) {
return ENOMEM;
}
NDINIT(&nd,
LOOKUP,
namei_simple_convert_flags(sflags),
pb);
if (dvp != NULL)
NDAT(&nd, dvp);
err = namei(&nd);
if (err != 0) {
pathbuf_destroy(pb);
return err;
}
*vp_ret = nd.ni_vp;
pathbuf_destroy(pb);
return 0;
}
int
namei_simple_user(const char *path, namei_simple_flags_t sflags,
struct vnode **vp_ret)
{
return nameiat_simple_user(NULL, path, sflags, vp_ret);
}
int
nameiat_simple_user(struct vnode *dvp, const char *path,
namei_simple_flags_t sflags, struct vnode **vp_ret)
{
struct pathbuf *pb;
struct nameidata nd;
int err;
err = pathbuf_copyin(path, &pb);
if (err) {
return err;
}
NDINIT(&nd,
LOOKUP,
namei_simple_convert_flags(sflags),
pb);
if (dvp != NULL)
NDAT(&nd, dvp);
err = namei(&nd);
if (err != 0) {
pathbuf_destroy(pb);
return err;
}
*vp_ret = nd.ni_vp;
pathbuf_destroy(pb);
return 0;
}
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