propagator/lomount.c

/*
 * Guillaume Cottenceau (gc@mandrakesoft.com)
 *
 * Copyright 2000 MandrakeSoft
 *
 * This software may be freely redistributed under the terms of the GNU
 * public license.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */

/* This code comes from util-linux-2.10n (mount/lomount.c)
 * (this is a simplified version of this code)
 */

#include <sys/types.h>
#include <sys/mount.h>
#include <sys/ioctl.h>
#include <sys/mount.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include "stage1.h"
#include "frontend.h"
#include "log.h"
#include "mount.h"
#include "modules.h"
#include "udev.h"

#include "lomount.h"


#define LO_NAME_SIZE	64
#define LO_KEY_SIZE	32

struct loop_info
{
	int		lo_number;	/* ioctl r/o */
	dev_t		lo_device; 	/* ioctl r/o */
	unsigned long	lo_inode; 	/* ioctl r/o */
	dev_t		lo_rdevice; 	/* ioctl r/o */
	int		lo_offset;
	int		lo_encrypt_type;
	int		lo_encrypt_key_size; 	/* ioctl w/o */
	int		lo_flags;	/* ioctl r/o */
	char		lo_name[LO_NAME_SIZE];
	unsigned char	lo_encrypt_key[LO_KEY_SIZE]; /* ioctl w/o */
	unsigned long	lo_init[2];
	char		reserved[4];
};

#define LOOP_SET_FD	0x4C00
#define LOOP_CLR_FD	0x4C01
#define LOOP_SET_STATUS	0x4C02
#define LOOP_GET_STATUS	0x4C03

int
set_loop (const char *device, const char *file)
{
	struct loop_info loopinfo;
	int i, fd, ffd, mode;

	mode = O_RDONLY;

	if ((ffd = open (file, mode)) < 0)
		return 1;

	for (i=3; i && (fd = open(device, mode)) < 0; --i, sleep(1));
	if (fd < 0) {
		close(ffd);
		return 1;
	}

	memset(&loopinfo, 0, sizeof (loopinfo));
	strncpy(loopinfo.lo_name, file, LO_NAME_SIZE);
	loopinfo.lo_name[LO_NAME_SIZE - 1] = 0;
	loopinfo.lo_offset = 0;

#ifdef MCL_FUTURE
	/*
	 * Oh-oh, sensitive data coming up. Better lock into memory to prevent
	 * passwd etc being swapped out and left somewhere on disk.
	 */

	  if(mlockall(MCL_CURRENT|MCL_FUTURE)) {
		  log_message("CRITICAL Couldn't lock into memory! %s (memlock)", strerror(errno));
		  return 1;
	  }
#endif

	if (ioctl(fd, LOOP_SET_FD, ffd) < 0) {
		close(fd);
		close(ffd);
		return 1;
	}
	/* Note: LOOP_SET_FD triggers change event. While processing it
	 * udev reads the loop device with builtin blkid. This can race
	 * with subsequent access by kernel due to LOOP_SET_STATUS (or
	 * mounting the loop device). Therefore give udev a chance to
	 * process the event without concurrent access to the loop device
	 */
	udev_settle();

	if (ioctl(fd, LOOP_SET_STATUS, &loopinfo) < 0) {
		(void) ioctl (fd, LOOP_CLR_FD, 0);
		close(fd);
		close(ffd);
		return 1;
	}

	/* Same here: LOOP_SET_STATUS triggers change event, give udev
	 * a chance to process it without concurrent access to the loop
	 * device. In other words, prevent the caller of this function
	 * from mounting the device while udev still running blkid on it
	 */
	udev_settle();

	close(fd);
	close(ffd);
	/* udev might be monitoring loopback device (with fanotify) and
	 * will synthesize a change event on close. Give udev some time
	 * to process without racing with the caller of this function
	 * (which is going to mount the newly configured loopback device)
	 */
	udev_settle();
	return 0;
}


char * loopdev = "/dev/loop3"; /* Ugly. But do I care? */

void del_loop(char *device)
{
	int fd;

	if ((fd = open (device, O_RDONLY)) < 0)
		return;

	if (ioctl (fd, LOOP_CLR_FD, 0) < 0)
		return;

	close (fd);
}


static char * where_mounted = NULL;

int
lomount(char *loopfile, char *where)
{

	long int flag;

	flag = MS_MGC_VAL;
	flag |= MS_RDONLY;

	my_insmod("loop", NULL);

	if (set_loop(loopdev, loopfile)) {
		log_message("set_loop failed on %s (%s)", loopdev, strerror(errno));
		return 1;
	}

	if (my_mount(loopdev, where, "iso9660", 0)) {
		del_loop(loopdev);
		return 1;
	}

	where_mounted = strdup(where);
	log_message("lomount succeeded for %s on %s", loopfile, where);
	return 0;
}


int
loumount()
{
	if (where_mounted) {
		umount(where_mounted);
		where_mounted = NULL;
	}
	del_loop(loopdev);
	return 0;
}