freebsd-skq/lib/libc/gen/opendir.c
jilles fba61ef227 libc: Use O_CLOEXEC for various internal file descriptors.
This fixes a race condition where another thread may fork() before CLOEXEC
is set, unintentionally passing the descriptor to the child process.

This commit only adds O_CLOEXEC flags to open() or openat() calls where no
fcntl(fd, F_SETFD, FD_CLOEXEC) follows. The separate fcntl() call still
leaves a race window so it should be fixed later.
2012-09-29 11:54:34 +00:00

317 lines
7.1 KiB
C

/*-
* Copyright (c) 1983, 1993
* The Regents of the University of California. All rights reserved.
*
* 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.
*/
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)opendir.c 8.8 (Berkeley) 5/1/95";
#endif /* LIBC_SCCS and not lint */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "namespace.h"
#include <sys/param.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "un-namespace.h"
#include "gen-private.h"
#include "telldir.h"
static DIR * __opendir_common(int, const char *, int);
/*
* Open a directory.
*/
DIR *
opendir(const char *name)
{
return (__opendir2(name, DTF_HIDEW|DTF_NODUP));
}
/*
* Open a directory with existing file descriptor.
*/
DIR *
fdopendir(int fd)
{
struct stat statb;
/* Check that fd is associated with a directory. */
if (_fstat(fd, &statb) != 0)
return (NULL);
if (!S_ISDIR(statb.st_mode)) {
errno = ENOTDIR;
return (NULL);
}
if (_fcntl(fd, F_SETFD, FD_CLOEXEC) == -1)
return (NULL);
return (__opendir_common(fd, NULL, DTF_HIDEW|DTF_NODUP));
}
DIR *
__opendir2(const char *name, int flags)
{
int fd;
DIR *dir;
int saved_errno;
if ((fd = _open(name,
O_RDONLY | O_NONBLOCK | O_DIRECTORY | O_CLOEXEC)) == -1)
return (NULL);
dir = __opendir_common(fd, name, flags);
if (dir == NULL) {
saved_errno = errno;
_close(fd);
errno = saved_errno;
}
return (dir);
}
static int
opendir_compar(const void *p1, const void *p2)
{
return (strcmp((*(const struct dirent **)p1)->d_name,
(*(const struct dirent **)p2)->d_name));
}
/*
* Common routine for opendir(3), __opendir2(3) and fdopendir(3).
*/
static DIR *
__opendir_common(int fd, const char *name, int flags)
{
DIR *dirp;
int incr;
int saved_errno;
int unionstack;
int fd2;
if ((dirp = malloc(sizeof(DIR) + sizeof(struct _telldir))) == NULL)
return (NULL);
dirp->dd_td = (struct _telldir *)((char *)dirp + sizeof(DIR));
LIST_INIT(&dirp->dd_td->td_locq);
dirp->dd_td->td_loccnt = 0;
/*
* Use the system page size if that is a multiple of DIRBLKSIZ.
* Hopefully this can be a big win someday by allowing page
* trades to user space to be done by _getdirentries().
*/
incr = getpagesize();
if ((incr % DIRBLKSIZ) != 0)
incr = DIRBLKSIZ;
/*
* Determine whether this directory is the top of a union stack.
*/
if (flags & DTF_NODUP) {
struct statfs sfb;
if (_fstatfs(fd, &sfb) < 0)
goto fail;
unionstack = !strcmp(sfb.f_fstypename, "unionfs")
|| (sfb.f_flags & MNT_UNION);
} else {
unionstack = 0;
}
if (unionstack) {
int len = 0;
int space = 0;
char *buf = 0;
char *ddptr = 0;
char *ddeptr;
int n;
struct dirent **dpv;
/*
* The strategy here is to read all the directory
* entries into a buffer, sort the buffer, and
* remove duplicate entries by setting the inode
* number to zero.
*/
do {
/*
* Always make at least DIRBLKSIZ bytes
* available to _getdirentries
*/
if (space < DIRBLKSIZ) {
space += incr;
len += incr;
buf = reallocf(buf, len);
if (buf == NULL)
goto fail;
ddptr = buf + (len - space);
}
n = _getdirentries(fd, ddptr, space, &dirp->dd_seek);
if (n > 0) {
ddptr += n;
space -= n;
}
} while (n > 0);
ddeptr = ddptr;
flags |= __DTF_READALL;
/*
* Re-open the directory.
* This has the effect of rewinding back to the
* top of the union stack and is needed by
* programs which plan to fchdir to a descriptor
* which has also been read -- see fts.c.
*/
if (flags & DTF_REWIND) {
if ((fd2 = _open(name, O_RDONLY | O_DIRECTORY |
O_CLOEXEC)) == -1) {
saved_errno = errno;
free(buf);
free(dirp);
errno = saved_errno;
return (NULL);
}
(void)_dup2(fd2, fd);
_close(fd2);
}
/*
* There is now a buffer full of (possibly) duplicate
* names.
*/
dirp->dd_buf = buf;
/*
* Go round this loop twice...
*
* Scan through the buffer, counting entries.
* On the second pass, save pointers to each one.
* Then sort the pointers and remove duplicate names.
*/
for (dpv = 0;;) {
n = 0;
ddptr = buf;
while (ddptr < ddeptr) {
struct dirent *dp;
dp = (struct dirent *) ddptr;
if ((long)dp & 03L)
break;
if ((dp->d_reclen <= 0) ||
(dp->d_reclen > (ddeptr + 1 - ddptr)))
break;
ddptr += dp->d_reclen;
if (dp->d_fileno) {
if (dpv)
dpv[n] = dp;
n++;
}
}
if (dpv) {
struct dirent *xp;
/*
* This sort must be stable.
*/
mergesort(dpv, n, sizeof(*dpv),
opendir_compar);
dpv[n] = NULL;
xp = NULL;
/*
* Scan through the buffer in sort order,
* zapping the inode number of any
* duplicate names.
*/
for (n = 0; dpv[n]; n++) {
struct dirent *dp = dpv[n];
if ((xp == NULL) ||
strcmp(dp->d_name, xp->d_name)) {
xp = dp;
} else {
dp->d_fileno = 0;
}
if (dp->d_type == DT_WHT &&
(flags & DTF_HIDEW))
dp->d_fileno = 0;
}
free(dpv);
break;
} else {
dpv = malloc((n+1) * sizeof(struct dirent *));
if (dpv == NULL)
break;
}
}
dirp->dd_len = len;
dirp->dd_size = ddptr - dirp->dd_buf;
} else {
dirp->dd_len = incr;
dirp->dd_size = 0;
dirp->dd_buf = malloc(dirp->dd_len);
if (dirp->dd_buf == NULL)
goto fail;
dirp->dd_seek = 0;
flags &= ~DTF_REWIND;
}
dirp->dd_loc = 0;
dirp->dd_fd = fd;
dirp->dd_flags = flags;
dirp->dd_lock = NULL;
/*
* Set up seek point for rewinddir.
*/
dirp->dd_rewind = telldir(dirp);
return (dirp);
fail:
saved_errno = errno;
free(dirp);
errno = saved_errno;
return (NULL);
}