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freebsd-dev/sys/kern/vfs_lookup.c
Pawel Jakub Dawidek 7008be5bd7 Change the cap_rights_t type from uint64_t to a structure that we can extend 
in the future in a backward compatible (API and ABI) way.

The cap_rights_t represents capability rights. We used to use one bit to
represent one right, but we are running out of spare bits. Currently the new
structure provides place for 114 rights (so 50 more than the previous
cap_rights_t), but it is possible to grow the structure to hold at least 285
rights, although we can make it even larger if 285 rights won't be enough.

The structure definition looks like this:

	struct cap_rights {
		uint64_t	cr_rights[CAP_RIGHTS_VERSION + 2];
	};

The initial CAP_RIGHTS_VERSION is 0.

The top two bits in the first element of the cr_rights[] array contain total
number of elements in the array - 2. This means if those two bits are equal to
0, we have 2 array elements.

The top two bits in all remaining array elements should be 0.
The next five bits in all array elements contain array index. Only one bit is
used and bit position in this five-bits range defines array index. This means
there can be at most five array elements in the future.

To define new right the CAPRIGHT() macro must be used. The macro takes two
arguments - an array index and a bit to set, eg.

	#define	CAP_PDKILL	CAPRIGHT(1, 0x0000000000000800ULL)

We still support aliases that combine few rights, but the rights have to belong
to the same array element, eg:

	#define	CAP_LOOKUP	CAPRIGHT(0, 0x0000000000000400ULL)
	#define	CAP_FCHMOD	CAPRIGHT(0, 0x0000000000002000ULL)

	#define	CAP_FCHMODAT	(CAP_FCHMOD | CAP_LOOKUP)

There is new API to manage the new cap_rights_t structure:

	cap_rights_t *cap_rights_init(cap_rights_t *rights, ...);
	void cap_rights_set(cap_rights_t *rights, ...);
	void cap_rights_clear(cap_rights_t *rights, ...);
	bool cap_rights_is_set(const cap_rights_t *rights, ...);

	bool cap_rights_is_valid(const cap_rights_t *rights);
	void cap_rights_merge(cap_rights_t *dst, const cap_rights_t *src);
	void cap_rights_remove(cap_rights_t *dst, const cap_rights_t *src);
	bool cap_rights_contains(const cap_rights_t *big, const cap_rights_t *little);

Capability rights to the cap_rights_init(), cap_rights_set(),
cap_rights_clear() and cap_rights_is_set() functions are provided by
separating them with commas, eg:

	cap_rights_t rights;

	cap_rights_init(&rights, CAP_READ, CAP_WRITE, CAP_FSTAT);

There is no need to terminate the list of rights, as those functions are
actually macros that take care of the termination, eg:

	#define	cap_rights_set(rights, ...)				\
		__cap_rights_set((rights), __VA_ARGS__, 0ULL)
	void __cap_rights_set(cap_rights_t *rights, ...);

Thanks to using one bit as an array index we can assert in those functions that
there are no two rights belonging to different array elements provided
together. For example this is illegal and will be detected, because CAP_LOOKUP
belongs to element 0 and CAP_PDKILL to element 1:

	cap_rights_init(&rights, CAP_LOOKUP | CAP_PDKILL);

Providing several rights that belongs to the same array's element this way is
correct, but is not advised. It should only be used for aliases definition.

This commit also breaks compatibility with some existing Capsicum system calls,
but I see no other way to do that. This should be fine as Capsicum is still
experimental and this change is not going to 9.x.

Sponsored by:	The FreeBSD Foundation
2013-09-05 00:09:56 +00:00

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/*-
* 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.
* 4. 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_kdtrace.h"
#include "opt_ktrace.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/capability.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, entry, "struct vnode *", "char *",
"unsigned long");
SDT_PROBE_DEFINE2(vfs, namei, lookup, return, return, "int", "struct vnode *");
/*
* Allocation zone for namei
*/
uma_zone_t namei_zone;
/*
* Placeholder vnode for mp traversal
*/
static struct vnode *vp_crossmp;
static void
nameiinit(void *dummy __unused)
{
namei_zone = uma_zcreate("NAMEI", MAXPATHLEN, NULL, NULL, NULL, NULL,
UMA_ALIGN_PTR, 0);
getnewvnode("crossmp", NULL, &dead_vnodeops, &vp_crossmp);
vn_lock(vp_crossmp, LK_EXCLUSIVE);
VN_LOCK_ASHARE(vp_crossmp);
VOP_UNLOCK(vp_crossmp, 0);
}
SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_SECOND, nameiinit, NULL);
static int lookup_shared = 1;
SYSCTL_INT(_vfs, OID_AUTO, lookup_shared, CTLFLAG_RW, &lookup_shared, 0,
"Enables/Disables shared locks for path name translation");
TUNABLE_INT("vfs.lookup_shared", &lookup_shared);
/*
* 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 uio auio;
int error, linklen;
struct componentname *cnp = &ndp->ni_cnd;
struct thread *td = cnp->cn_thread;
struct proc *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"));
if (!lookup_shared)
cnp->cn_flags &= ~LOCKSHARED;
fdp = p->p_fd;
/* 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, (size_t *)&ndp->ni_pathlen);
else
error = copyinstr(ndp->ni_dirp, cnp->cn_pnbuf,
MAXPATHLEN, (size_t *)&ndp->ni_pathlen);
/*
* Don't allow empty pathnames.
*/
if (!error && *cnp->cn_pnbuf == '\0')
error = ENOENT;
#ifdef CAPABILITY_MODE
/*
* In capability mode, lookups must be "strictly relative" (i.e.
* not an absolute path, and not containing '..' components) to
* a real file descriptor, not the pseudo-descriptor AT_FDCWD.
*/
if (error == 0 && IN_CAPABILITY_MODE(td) &&
(cnp->cn_flags & NOCAPCHECK) == 0) {
ndp->ni_strictrelative = 1;
if (ndp->ni_dirfd == AT_FDCWD) {
#ifdef KTRACE
if (KTRPOINT(td, KTR_CAPFAIL))
ktrcapfail(CAPFAIL_LOOKUP, 0, 0);
#endif
error = ECAPMODE;
}
}
#endif
if (error) {
uma_zfree(namei_zone, cnp->cn_pnbuf);
#ifdef DIAGNOSTIC
cnp->cn_pnbuf = NULL;
cnp->cn_nameptr = NULL;
#endif
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;
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);
dp = NULL;
if (cnp->cn_pnbuf[0] != '/') {
if (ndp->ni_startdir != NULL) {
dp = ndp->ni_startdir;
error = 0;
} else if (ndp->ni_dirfd != AT_FDCWD) {
cap_rights_t rights;
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);
error = fgetvp_rights(td, ndp->ni_dirfd,
&rights, &ndp->ni_filecaps, &dp);
#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_strictrelative = 1;
}
#endif
}
if (error != 0 || dp != NULL) {
FILEDESC_SUNLOCK(fdp);
if (error == 0 && dp->v_type != VDIR) {
vrele(dp);
error = ENOTDIR;
}
}
if (error) {
uma_zfree(namei_zone, cnp->cn_pnbuf);
#ifdef DIAGNOSTIC
cnp->cn_pnbuf = NULL;
cnp->cn_nameptr = NULL;
#endif
return (error);
}
}
if (dp == NULL) {
dp = fdp->fd_cdir;
VREF(dp);
FILEDESC_SUNLOCK(fdp);
if (ndp->ni_startdir != NULL)
vrele(ndp->ni_startdir);
}
SDT_PROBE(vfs, namei, lookup, entry, dp, cnp->cn_pnbuf,
cnp->cn_flags, 0, 0);
for (;;) {
/*
* Check if root directory should replace current directory.
* Done at start of translation and after symbolic link.
*/
cnp->cn_nameptr = cnp->cn_pnbuf;
if (*(cnp->cn_nameptr) == '/') {
vrele(dp);
if (ndp->ni_strictrelative != 0) {
#ifdef KTRACE
if (KTRPOINT(curthread, KTR_CAPFAIL))
ktrcapfail(CAPFAIL_LOOKUP, 0, 0);
#endif
return (ENOTCAPABLE);
}
while (*(cnp->cn_nameptr) == '/') {
cnp->cn_nameptr++;
ndp->ni_pathlen--;
}
dp = ndp->ni_rootdir;
VREF(dp);
}
ndp->ni_startdir = dp;
error = lookup(ndp);
if (error) {
uma_zfree(namei_zone, cnp->cn_pnbuf);
#ifdef DIAGNOSTIC
cnp->cn_pnbuf = NULL;
cnp->cn_nameptr = NULL;
#endif
SDT_PROBE(vfs, namei, lookup, return, error, NULL, 0,
0, 0);
return (error);
}
/*
* If not a symbolic link, we're done.
*/
if ((cnp->cn_flags & ISSYMLINK) == 0) {
if ((cnp->cn_flags & (SAVENAME | SAVESTART)) == 0) {
uma_zfree(namei_zone, cnp->cn_pnbuf);
#ifdef DIAGNOSTIC
cnp->cn_pnbuf = NULL;
cnp->cn_nameptr = NULL;
#endif
} else
cnp->cn_flags |= HASBUF;
SDT_PROBE(vfs, namei, lookup, return, 0, ndp->ni_vp,
0, 0, 0);
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)
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) {
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;
}
uma_zfree(namei_zone, cnp->cn_pnbuf);
#ifdef DIAGNOSTIC
cnp->cn_pnbuf = NULL;
cnp->cn_nameptr = NULL;
#endif
vput(ndp->ni_vp);
ndp->ni_vp = NULL;
vrele(ndp->ni_dvp);
SDT_PROBE(vfs, namei, lookup, return, error, NULL, 0, 0, 0);
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;
}
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) {
if (mp != NULL &&
(mp->mnt_kern_flag & MNTK_EXTENDED_SHARED))
return (0);
else
return (1);
}
/*
* 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 */
struct vnode *dp = 0; /* the directory we are searching */
struct vnode *tdp; /* saved dp */
struct mount *mp; /* mount table entry */
struct prison *pr;
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 */
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.
*/
if (lookup_shared)
cnp->cn_lkflags = LK_SHARED;
else
cnp->cn_lkflags = LK_EXCLUSIVE;
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.
*/
cnp->cn_consume = 0;
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
ndp->ni_pathlen -= cnp->cn_namelen;
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;
}
/*
* 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, return ENOTCAPABLE (this is a
* fairly conservative design choice, but it's the only one that we
* are satisfied guarantees the property we're looking for).
* 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.
*/
if (cnp->cn_flags & ISDOTDOT) {
if (ndp->ni_strictrelative != 0) {
#ifdef KTRACE
if (KTRPOINT(curthread, KTR_CAPFAIL))
ktrcapfail(CAPFAIL_LOOKUP, 0, 0);
#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));
}
}
/*
* 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 (dp != vp_crossmp &&
VOP_ISLOCKED(dp) == LK_SHARED &&
(cnp->cn_flags & ISLASTCN) && (cnp->cn_flags & LOCKPARENT))
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
vprint("lookup in", dp);
#endif
lkflags_save = cnp->cn_lkflags;
cnp->cn_lkflags = compute_cn_lkflags(dp->v_mount, cnp->cn_lkflags,
cnp->cn_flags);
if ((error = VOP_LOOKUP(dp, &ndp->ni_vp, cnp)) != 0) {
cnp->cn_lkflags = lkflags_save;
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));
goto unionlookup;
}
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;
} else
cnp->cn_lkflags = lkflags_save;
#ifdef NAMEI_DIAGNOSTIC
printf("found\n");
#endif
/*
* Take into account any additional components consumed by
* the underlying filesystem.
*/
if (cnp->cn_consume > 0) {
cnp->cn_nameptr += cnp->cn_consume;
ndp->ni_next += cnp->cn_consume;
ndp->ni_pathlen -= cnp->cn_consume;
cnp->cn_consume = 0;
}
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);
vref(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 (*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 lookup_shared 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 = 0; /* 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
vprint("search in:", dp);
#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_strictrelative = 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_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_UNLOCK) &&
(ndp->ni_cnd.cn_flags & LOCKPARENT) &&
ndp->ni_dvp != ndp->ni_vp)
unlock_dvp = 1;
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 compatiblity 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, FOLLOW, UIO_SYSSPACE, buf, td);
error = namei(&nd);
*cp = '/';
if (error != 0)
goto keeporig;
} else {
NDINIT(&nd, LOOKUP, FOLLOW, 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);
}
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