client/umount.cifs.c

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/* 
   Unmount utility program for Linux CIFS VFS (virtual filesystem) client
   Copyright (C) 2005 Steve French  (sfrench@us.ibm.com)

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   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.  */

#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <ctype.h>
#include <sys/types.h>
#include <sys/mount.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/vfs.h>
#include <fcntl.h>
#include <getopt.h>
#include <errno.h>
#include <string.h>
#include <mntent.h>

#define UNMOUNT_CIFS_VERSION_MAJOR "0"
#define UNMOUNT_CIFS_VERSION_MINOR "5"

#ifndef UNMOUNT_CIFS_VENDOR_SUFFIX
 #ifdef _SAMBA_BUILD_
  #include "include/version.h"
  #ifdef SAMBA_VERSION_VENDOR_SUFFIX
   #define UNMOUNT_CIFS_VENDOR_SUFFIX "-"SAMBA_VERSION_OFFICIAL_STRING"-"SAMBA_VERSION_VENDOR_SUFFIX
  #else
   #define UNMOUNT_CIFS_VENDOR_SUFFIX "-"SAMBA_VERSION_OFFICIAL_STRING
  #endif /* SAMBA_VERSION_OFFICIAL_STRING and SAMBA_VERSION_VENDOR_SUFFIX */
 #else
  #define UNMOUNT_CIFS_VENDOR_SUFFIX ""
 #endif /* _SAMBA_BUILD_ */
#endif /* UNMOUNT_CIFS_VENDOR_SUFFIX */

#ifndef MNT_DETACH
#define MNT_DETACH 0x02
#endif

#ifndef MNT_EXPIRE
#define MNT_EXPIRE 0x04
#endif

#ifndef MOUNTED_LOCK
#define MOUNTED_LOCK    "/etc/mtab~"
#endif
#ifndef MOUNTED_TEMP
#define MOUNTED_TEMP    "/etc/mtab.tmp"
#endif

#define CIFS_IOC_CHECKUMOUNT _IO(0xCF, 2)
#define CIFS_MAGIC_NUMBER 0xFF534D42   /* the first four bytes of SMB PDU */
   
static struct option longopts[] = {
        { "all", 0, NULL, 'a' },
        { "help",0, NULL, 'h' },
        { "read-only", 0, NULL, 'r' },
        { "ro", 0, NULL, 'r' },
        { "verbose", 0, NULL, 'v' },
        { "version", 0, NULL, 'V' },
        { "expire", 0, NULL, 'e' },
        { "force", 0, 0, 'f' },
        { "lazy", 0, 0, 'l' },
        { "no-mtab", 0, 0, 'n' },
        { NULL, 0, NULL, 0 }
};

const char * thisprogram;
int verboseflg = 0;

static void umount_cifs_usage(void)
{
        printf("\nUsage:  %s <remotetarget> <dir>\n", thisprogram);
        printf("\nUnmount the specified directory\n");
        printf("\nLess commonly used options:");
        printf("\n\t-r\tIf mount fails, retry with readonly remount.");
        printf("\n\t-n\tDo not write to mtab.");
        printf("\n\t-f\tAttempt a forced unmount, even if the fs is busy.");
        printf("\n\t-l\tAttempt lazy unmount, Unmount now, cleanup later.");
        printf("\n\t-v\tEnable verbose mode (may be useful for debugging).");
        printf("\n\t-h\tDisplay this help.");
        printf("\n\nOptions are described in more detail in the manual page");
        printf("\n\tman 8 umount.cifs\n");
        printf("\nTo display the version number of the cifs umount utility:");
        printf("\n\t%s -V\n",thisprogram);
        printf("\nInvoking the umount utility on cifs mounts, can execute");
        printf(" /sbin/umount.cifs (if present and umount -i is not specified.\n");
}

static int umount_check_perm(char * dir)
{
        int fileid;
        int rc;

        /* allow root to unmount, no matter what */
        if(getuid() == 0)
                return 0;

        /* presumably can not chdir into the target as we do on mount */
        fileid = open(dir, O_RDONLY | O_DIRECTORY | O_NOFOLLOW, 0);
        if(fileid == -1) {
                if(verboseflg)
                        printf("error opening mountpoint %d %s",errno,strerror(errno));
                return errno;
        }

        rc = ioctl(fileid, CIFS_IOC_CHECKUMOUNT, NULL);

        if(verboseflg)
                printf("ioctl returned %d with errno %d %s\n",rc,errno,strerror(errno));

        if(rc == ENOTTY) {
                printf("user unmounting via %s is an optional feature of",thisprogram);
                printf(" the cifs filesystem driver (cifs.ko)");
                printf("\n\tand requires cifs.ko version 1.32 or later\n");
        } else if (rc != 0)
                printf("user unmount of %s failed with %d %s\n",dir,errno,strerror(errno));
        close(fileid);

        return rc;
}

static int lock_mtab(void)
{
        int rc;
        
        rc = mknod(MOUNTED_LOCK , 0600, 0);
        if(rc == -1)
                printf("\ngetting lock file %s failed with %s\n",MOUNTED_LOCK,
                                strerror(errno));
                
        return rc;      
        
}

static void unlock_mtab(void)
{
        unlink(MOUNTED_LOCK);   
}

static int remove_from_mtab(char * mountpoint)
{
        int rc;
        int num_matches;
        FILE * org_fd;
        FILE * new_fd;
        struct mntent * mount_entry;

        /* Do we need to check if it is a symlink to e.g. /proc/mounts
        in which case we probably do not want to update it? */

        /* Do we first need to check if it is writable? */ 

        if (lock_mtab()) {
                printf("Mount table locked\n");
                return -EACCES;
        }
        
        if(verboseflg)
                printf("attempting to remove from mtab\n");

        org_fd = setmntent(MOUNTED, "r");

        if(org_fd == NULL) {
                printf("Can not open %s\n",MOUNTED);
                unlock_mtab();
                return -EIO;
        }

        new_fd = setmntent(MOUNTED_TEMP,"w");
        if(new_fd == NULL) {
                printf("Can not open temp file %s", MOUNTED_TEMP);
                endmntent(org_fd);
                unlock_mtab();
                return -EIO;
        }

        /* BB fix so we only remove the last entry that matches BB */
        num_matches = 0;
        while((mount_entry = getmntent(org_fd)) != NULL) {
                if(strcmp(mount_entry->mnt_dir, mountpoint) == 0) {
                        num_matches++;
                }
        }       
        if(verboseflg)
                printf("%d matching entries in mount table\n", num_matches);
                
        /* Is there a better way to seek back to the first entry in mtab? */
        endmntent(org_fd);
        org_fd = setmntent(MOUNTED, "r");

        if(org_fd == NULL) {
                printf("Can not open %s\n",MOUNTED);
                unlock_mtab();
                return -EIO;
        }
        
        while((mount_entry = getmntent(org_fd)) != NULL) {
                if(strcmp(mount_entry->mnt_dir, mountpoint) != 0) {
                        addmntent(new_fd, mount_entry);
                } else {
                        if(num_matches != 1) {
                                addmntent(new_fd, mount_entry);
                                num_matches--;
                        } else if(verboseflg)
                                printf("entry not copied (ie entry is removed)\n");
                }
        }

        if(verboseflg)
                printf("done updating tmp file\n");
        rc = fchmod (fileno (new_fd), S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH);
        if(rc < 0) {
                printf("error %s changing mode of %s\n", strerror(errno),
                        MOUNTED_TEMP);
        }
        endmntent(new_fd);

        rc = rename(MOUNTED_TEMP, MOUNTED);

        if(rc < 0) {
                printf("failure %s renaming %s to %s\n",strerror(errno),
                        MOUNTED_TEMP, MOUNTED);
                unlock_mtab();
                return -EIO;
        }

        unlock_mtab();
        
        return rc;
}

int main(int argc, char ** argv)
{
        int c;
        int rc;
        int flags = 0;
        int nomtab = 0;
        int retry_remount = 0;
        struct statfs statbuf;
        char * mountpoint;

        if(argc && argv) {
                thisprogram = argv[0];
        } else {
                umount_cifs_usage();
                return -EINVAL;
        }

        if(argc < 2) {
                umount_cifs_usage();
                return -EINVAL;
        }

        if(thisprogram == NULL)
                thisprogram = "umount.cifs";

        /* add sharename in opts string as unc= parm */

        while ((c = getopt_long (argc, argv, "afhilnrvV",
                         longopts, NULL)) != -1) {
                switch (c) {
/* No code to do the following  option yet */
/*              case 'a':              
                        ++umount_all;
                        break; */
                case '?':
                case 'h':   /* help */
                        umount_cifs_usage();
                        exit(1);
                case 'n':
                        ++nomtab;
                        break;
                case 'f':
                        flags |= MNT_FORCE;
                        break;
                case 'l':
                        flags |= MNT_DETACH; /* lazy unmount */
                        break;
                case 'e':
                        flags |= MNT_EXPIRE; /* gradually timeout */
                        break;
                case 'r':
                        ++retry_remount;
                        break;
                case 'v':
                        ++verboseflg;
                        break;
                case 'V':          
                        printf ("umount.cifs version: %s.%s%s\n",
                                UNMOUNT_CIFS_VERSION_MAJOR,
                                UNMOUNT_CIFS_VERSION_MINOR,
                                UNMOUNT_CIFS_VENDOR_SUFFIX);
                        exit (0);
                default:
                        printf("unknown unmount option %c\n",c);
                        umount_cifs_usage();
                        exit(1);
                }
        }

        /* move past the umount options */
        argv += optind;
        argc -= optind;

        mountpoint = argv[0];

        if((argc < 1) || (argv[0] == NULL)) {
                printf("\nMissing name of unmount directory\n");
                umount_cifs_usage();
                return -EINVAL;
        }

        if(verboseflg)
                printf("optind %d unmount dir %s\n",optind, mountpoint);

        /* check if running effectively root */
        if(geteuid() != 0) {
                printf("Trying to unmount when %s not installed suid\n",thisprogram);
                if(verboseflg)
                        printf("euid = %d\n",geteuid());
                return -EACCES;
        }

        /* fixup path if needed */

        /* Trim any trailing slashes */
        while ((strlen(mountpoint) > 1) &&
                (mountpoint[strlen(mountpoint)-1] == '/'))
        {
                mountpoint[strlen(mountpoint)-1] = '\0';
        }

        /* make sure that this is a cifs filesystem */
        rc = statfs(mountpoint, &statbuf);
        
        if(rc || (statbuf.f_type != CIFS_MAGIC_NUMBER)) {
                printf("This utility only unmounts cifs filesystems.\n");
                return -EINVAL;
        }

        /* check if our uid was the one who mounted */
        rc = umount_check_perm(mountpoint);
        if (rc) {
                printf("Not permitted to unmount\n");
                return rc;
        }

        if(umount2(mountpoint, flags)) {
        /* remember to kill daemon on error */
                switch (errno) {
                case 0:
                        printf("unmount failed but no error number set\n");
                        break;
                default:
                        printf("unmount error %d = %s\n",errno,strerror(errno));
                }
                printf("Refer to the umount.cifs(8) manual page (man 8 umount.cifs)\n");
                return -1;
        } else {
                if(verboseflg)
                        printf("umount2 succeeded\n");
                if(nomtab == 0)
                        remove_from_mtab(mountpoint);
        }

        return 0;
}

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