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NetBSD/sys/kern/vfs_getcwd.c

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/* $NetBSD: vfs_getcwd.c,v 1.6 1999/04/30 18:43:00 thorpej Exp $ */
/*-
* Copyright (c) 1999 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Bill Sommerfeld.
*
* 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. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the NetBSD
* Foundation, Inc. and its contributors.
* 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/namei.h>
#include <sys/filedesc.h>
#include <sys/kernel.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/proc.h>
#include <sys/uio.h>
#include <sys/malloc.h>
#include <sys/dirent.h>
#include <ufs/ufs/dir.h> /* XXX only for DIRBLKSIZ */
#include <sys/syscallargs.h>
static int
getcwd_scandir __P((struct vnode *, struct vnode **,
char **, char *, struct proc *));
static int
getcwd_getcache __P((struct vnode **, struct vnode **,
char **, char *));
static int
getcwd_common __P((struct vnode *, struct vnode *,
char **, char *, int, int, struct proc *));
int vn_isunder __P((struct vnode *, struct vnode *, struct proc *));
#define DIRENT_MINSIZE (sizeof(struct dirent) - (MAXNAMLEN+1) + 4)
/*
* XXX Will infinite loop in certain cases if a directory read reliably
* returns EINVAL on last block.
* XXX is EINVAL the right thing to return if a directory is malformed?
*/
/*
* Find parent vnode of cvp, return in *pvpp
* Scan it looking for name of directory entry pointing at cvp.
*
* Place the name in the buffer which starts at bufp, immediately
* before *bpp, and move bpp backwards to point at the start of it.
*/
static int
getcwd_scandir(cvp, pvpp, bpp, bufp, p)
struct vnode *cvp;
struct vnode **pvpp;
char **bpp;
char *bufp;
struct proc *p;
{
int error = 0;
int eofflag;
off_t off;
int tries;
struct uio uio;
struct iovec iov;
char *dirbuf = NULL;
int dirbuflen;
ino_t fileno;
struct vattr va;
struct vnode *pvp = NULL;
struct componentname cn;
int len, reclen;
tries = 0;
/*
* Ok, we have to do it the hard way..
* First, get parent vnode using lookup of ..
*/
cn.cn_nameiop = LOOKUP;
cn.cn_flags = ISLASTCN | ISDOTDOT | RDONLY | LOCKPARENT;
cn.cn_proc = p;
cn.cn_cred = p->p_ucred;
cn.cn_pnbuf = NULL;
cn.cn_nameptr = "..";
cn.cn_namelen = 2;
cn.cn_hash = 0;
cn.cn_consume = 0;
/*
* At this point, cvp is locked, and will be locked
* on return in all cases.
* On successful return, *pvpp will also be locked
*/
error = VOP_LOOKUP(cvp, pvpp, &cn);
if (error) {
*pvpp = NULL;
return error;
}
pvp = *pvpp;
/* If we don't care about the pathname, we're done */
if (bufp == NULL)
return 0;
error = VOP_GETATTR(cvp, &va, p->p_ucred, p);
if (error)
return error;
fileno = va.va_fileid;
dirbuflen = DIRBLKSIZ;
if (dirbuflen < va.va_blocksize)
dirbuflen = va.va_blocksize;
dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK);
#if 0
unionread:
#endif
off = 0;
do {
/* call VOP_READDIR of parent */
iov.iov_base = dirbuf;
iov.iov_len = dirbuflen;
uio.uio_iov = &iov;
uio.uio_iovcnt = 1;
uio.uio_offset = off;
uio.uio_resid = dirbuflen;
uio.uio_segflg = UIO_SYSSPACE;
uio.uio_rw = UIO_READ;
uio.uio_procp = p;
eofflag = 0;
/* XXX un-break adosfs */
VOP_UNLOCK(cvp, 0);
error = VOP_READDIR(pvp, &uio, p->p_ucred, &eofflag, 0, 0);
/* XXX not handling lock failures here.. */
(void) vn_lock(cvp, LK_EXCLUSIVE | LK_RETRY);
off = uio.uio_offset;
/*
* Try again if NFS tosses its cookies.
* XXX this can still loop forever if the directory is busted
* such that the second or subsequent page of it always
* returns EINVAL
*/
if ((error == EINVAL) && (tries < 3)) {
off = 0;
tries++;
continue; /* once more, with feeling */
}
if (!error) {
char *cpos;
struct dirent *dp;
cpos = dirbuf;
tries = 0;
/* scan directory page looking for matching vnode */
for (len = (dirbuflen - uio.uio_resid); len > 0; len -= reclen) {
dp = (struct dirent *) cpos;
reclen = dp->d_reclen;
/* check for malformed directory.. */
if (reclen < DIRENT_MINSIZE) {
error = EINVAL;
goto out;
}
/*
* XXX should perhaps do VOP_LOOKUP to
* check that we got back to the right place,
* but getting the locking games for that
* right would be heinous.
*/
if ((dp->d_type != DT_WHT) &&
(dp->d_fileno == fileno)) {
char *bp = *bpp;
bp -= dp->d_namlen;
if (bp <= bufp) {
error = ERANGE;
goto out;
}
memcpy(bp, dp->d_name, dp->d_namlen);
error = 0;
*bpp = bp;
goto out;
}
cpos += reclen;
}
}
} while (!eofflag);
#if 0
/*
* Deal with mount -o union, which unions only the
* root directory of the mount.
*/
if ((pvp->v_flag & VROOT) &&
(pvp->v_mount->mnt_flag & MNT_UNION)) {
struct vnode *tvp = pvp;
pvp = pvp->v_mount->mnt_vnodecovered;
vput(tvp);
VREF(pvp);
*pvpp = pvp;
error = vn_lock(pvp, LK_EXCLUSIVE | LK_RETRY);
if (error != 0) {
vrele(pvp);
*pvpp = pvp = NULL;
goto out;
}
goto unionread;
}
#endif
error = ENOENT;
out:
free(dirbuf, M_TEMP);
return error;
}
/*
* Look in the vnode-to-name reverse cache to see if
* we can find things the easy way.
*
* XXX vn_lock/vget failure paths are untested.
*/
static int
getcwd_getcache(vpp, dvpp, bpp, bufp)
struct vnode **vpp, **dvpp;
char **bpp;
char *bufp;
{
struct vnode *cvp, *pvp = NULL;
int error;
cvp = *vpp;
error = cache_revlookup(cvp, dvpp, bpp, bufp);
if (error)
return error;
pvp = *dvpp;
/*
* Do a little dance with the locks to avoid deadlocking
* someone going the other way. Since we're going up, we have
* to release the current lock before we take the parent lock,
* and then re-take the current lock. Since either lock can
* fail, causing us to abort, this is a little convoluted.
*/
VOP_UNLOCK(cvp, 0);
/* cur now unlocked... */
error = vget(pvp, LK_EXCLUSIVE | LK_RETRY);
if (error != 0) {
vrele(cvp);
*vpp = NULL;
*dvpp = NULL;
return error;
}
/* parent is now locked */
error = vn_lock(cvp, LK_EXCLUSIVE | LK_RETRY);
if (error != 0) {
vrele(cvp);
*vpp = NULL;
return error;
}
/* ok, cur is now locked again.. */
return 0;
}
/*
* common routine shared by sys___getcwd() and vn_isunder()
*/
#define GETCWD_CHECK_ACCESS 0x0001
static int getcwd_common (dvp, rvp, bpp, bufp, limit, flags, p)
struct vnode *dvp;
struct vnode *rvp;
char **bpp;
char *bufp;
int limit;
int flags;
struct proc *p;
{
struct cwdinfo *cwdi = p->p_cwdi;
struct vnode *pvp = NULL;
char *bp = NULL;
int error;
if (rvp == NULL) {
rvp = cwdi->cwdi_rdir;
if (rvp == NULL)
rvp = rootvnode;
}
VREF(rvp);
VREF(dvp);
/*
* Error handling invariant:
* Before a `goto out':
* dvp is either NULL, or locked and held.
* pvp is either NULL, or locked and held.
*/
error = vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY);
if (error) {
vrele(dvp);
dvp = NULL;
goto out;
}
if (bufp)
bp = *bpp;
/*
* this loop will terminate when one of the following happens:
* - we hit the root
* - getdirentries or lookup fails
* - we run out of space in the buffer.
*/
if (dvp == rvp) {
if (bufp)
*(--(*bpp)) = '/';
goto out;
}
do {
if (dvp->v_type != VDIR) {
error = ENOTDIR;
goto out;
}
/*
* access check here is optional, depending on
* whether or not caller cares.
*/
if (flags & GETCWD_CHECK_ACCESS) {
error = VOP_ACCESS(dvp, VEXEC|VREAD, p->p_ucred, p);
if (error)
goto out;
}
/*
* step up if we're a covered vnode..
*/
while (dvp->v_flag & VROOT) {
struct vnode *tvp;
if (dvp == rvp)
goto out;
tvp = dvp;
dvp = dvp->v_mount->mnt_vnodecovered;
vput(tvp);
/*
* hodie natus est radici frater
*/
if (dvp == NULL) {
error = ENOENT;
goto out;
}
VREF(dvp);
error = vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY);
if (error != 0) {
vrele(dvp);
dvp = NULL;
goto out;
}
}
/*
* Look in the name cache; if that fails, look in the
* directory..
*/
error = getcwd_getcache(&dvp, &pvp, bpp, bufp);
if (error == -1)
error = getcwd_scandir(dvp, &pvp, bpp, bufp, p);
if (error)
goto out;
#if DIAGNOSTIC
if (dvp == pvp) {
panic("getcwd: oops, dvp == pvp");
}
if (bufp && (bp <= bufp)) {
panic("getcwd: oops, went back too far");
}
#endif
if (bufp) *(--(*bpp)) = '/';
vput(dvp);
dvp = pvp;
pvp = NULL;
limit--;
} while ((dvp != rvp) && (limit > 0));
out:
if (pvp)
vput(pvp);
if (dvp)
vput(dvp);
vrele(rvp);
return error;
}
/*
* Check if one directory can be found inside another in the directory
* hierarchy.
*
* Intended to be used in chroot, chdir, fchdir, etc., to ensure that
* chroot() actually means something.
*/
int vn_isunder(dvp, rvp, p)
struct vnode *dvp;
struct vnode *rvp;
struct proc *p;
{
int error;
error = getcwd_common (dvp, rvp, NULL, NULL, MAXPATHLEN/2, 0, p);
if (!error)
return 1;
else
return 0;
}
/*
* Returns true if proc p1's root directory equal to or under p2's
* root directory.
*
* Intended to be used from ptrace/procfs sorts of things.
*/
int proc_isunder (p1, p2)
struct proc *p1;
struct proc *p2;
{
struct vnode *r1 = p1->p_cwdi->cwdi_rdir;
struct vnode *r2 = p2->p_cwdi->cwdi_rdir;
if (r1 == NULL)
return (r2 == NULL);
else if (r2 == NULL)
return 1;
else
return vn_isunder(r1, r2, p2);
}
int sys___getcwd(p, v, retval)
struct proc *p;
void *v;
register_t *retval;
{
register struct sys___getcwd_args /* {
syscallarg(char *) bufp;
syscallarg(size_t) length;
} */ *uap = v;
int error;
char *path;
char *bp, *bend;
int len = SCARG(uap, length);
int lenused;
if ((len < 2) || (len > MAXPATHLEN*4))
return ERANGE;
path = (char *)malloc(len, M_TEMP, M_WAITOK);
if (!path)
return ENOMEM;
bp = &path[len];
bend = bp;
*(--bp) = '\0';
error = getcwd_common (p->p_cwdi->cwdi_cdir, NULL, &bp, path, len/2,
GETCWD_CHECK_ACCESS, p);
if (error)
goto out;
lenused = bend - bp;
*retval = lenused;
/* put the result into user buffer */
error = copyout(bp, SCARG(uap, bufp), lenused);
out:
free(path, M_TEMP);
return error;
}
/*
* Find pathname of process's current directory.
*
* Use vfs vnode-to-name reverse cache; if that fails, fall back
* to reading directory contents.
*/
/*
* XXX Untested vs. mount -o union; probably does the wrong thing.
* XXX Untested vs chroot
* XXX most error paths probably work, but many locking-related ones
* aren't tested well.
*/
#if 0
int
sys___getcwd(p, v, retval)
struct proc *p;
void *v;
register_t *retval;
{
register struct sys___getcwd_args /* {
syscallarg(char *) bufp;
syscallarg(size_t) length;
} */ *uap = v;
struct cwdinfo *cwdi = p->p_cwdi;
struct vnode *cvp = NULL, *pvp = NULL, *rootvp = NULL;
int error;
char *path;
char *bp, *bend;
int len = SCARG(uap, length);
int lenused;
if ((len < 2) || (len > MAXPATHLEN*4))
return ERANGE;
path = (char *)malloc(len, M_TEMP, M_WAITOK);
if (!path)
return ENOMEM;
bp = &path[len];
bend = bp;
*(--bp) = '\0';
rootvp = cwdi->cwdi_rdir;
if (rootvp == NULL)
rootvp = rootvnode;
cvp = cwdi->cwdi_cdir;
VREF(rootvp);
VREF(cvp);
/*
* Error handling invariant:
* Before a `goto out':
* cvp is either NULL, or locked and held.
* pvp is either NULL, or locked and held.
*/
error = vn_lock(cvp, LK_EXCLUSIVE | LK_RETRY);
if (error) {
vrele(cvp);
cvp = NULL;
goto out;
}
/*
* this loop will terminate when one of the following happens:
* - we hit the root
* - getdirentries or lookup fails
* - we run out of space in the buffer.
*/
if (cvp == rootvp) {
*(--bp) = '/';
goto hitroot;
}
do {
/*
* so, are we even allowed to look at this directory?
*/
error = VOP_ACCESS(cvp, VEXEC|VREAD, p->p_ucred, p);
if (error)
goto out;
/*
* step up if we're a covered vnode..
*/
while (cvp->v_flag & VROOT) {
struct vnode *tvp;
if (cvp == rootvp)
goto hitroot;
tvp = cvp;
cvp = cvp->v_mount->mnt_vnodecovered;
vput(tvp);
VREF(cvp);
error = vn_lock(cvp, LK_EXCLUSIVE | LK_RETRY);
if (error != 0) {
vrele(cvp);
cvp = NULL;
goto out;
}
}
/*
* Look in the name cache; if that fails, look in the directory..
*/
error = getcwd_getcache(&cvp, &pvp, &bp, path);
if (error == -1)
error = getcwd_scandir(cvp, &pvp, &bp, path, p);
if (error)
goto out;
if (bp <= path) {
error = ERANGE;
goto out;
}
*(--bp) = '/';
vput(cvp);
cvp = pvp;
pvp = NULL;
} while (cvp != rootvp);
hitroot:
lenused = bend - bp;
*retval = lenused;
/* put the result into user buffer */
error = copyout(bp, SCARG(uap, bufp), lenused);
out:
if (pvp)
vput(pvp);
if (cvp)
vput(cvp);
vrele(rootvp);
free(path, M_TEMP);
return error;
}
#endif
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