mount.c

Util-linux 软件包包含许多工具。其中比较重要的是加载、卸载、格式化、分区和管理硬盘驱动器

/*
 * A mount(8) for Linux 0.99.
 * mount.c,v 1.1.1.1 1993/11/18 08:40:51 jrs Exp
 *
 * Modifications by many people. Distributed under GPL.
 */

#include <unistd.h>
#include <ctype.h>
#include <errno.h>
#include <string.h>
#include <getopt.h>
#include <stdio.h>

#include <pwd.h>
#include <grp.h>

#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/mount.h>

#include "mount_blkid.h"
#include "mount_constants.h"
#include "sundries.h"
#include "mntent.h"
#include "fstab.h"
#include "lomount.h"
#include "loop.h"
#include "linux_fs.h"		/* for BLKGETSIZE */
#include "mount_guess_rootdev.h"
#include "mount_guess_fstype.h"
#include "mount_by_label.h"
#include "getusername.h"
#include "paths.h"
#include "env.h"
#include "nls.h"

#define DO_PS_FIDDLING

#ifdef DO_PS_FIDDLING
#include "setproctitle.h"
#endif

/* True for fake mount (-f).  */
static int fake = 0;

/* True if we are allowed to call /sbin/mount.${FSTYPE} */
static int external_allowed = 1;

/* Don't write a entry in /etc/mtab (-n).  */
static int nomtab = 0;

/* True for explicit readonly (-r).  */
static int readonly = 0;

/* Nonzero for chatty (-v).  */
int verbose = 0;

/* Nonzero for sloppy (-s).  */
int sloppy = 0;

/* True for explicit read/write (-w).  */
static int readwrite = 0;

/* True for all mount (-a).  */
int mount_all = 0;

/* True for fork() during all mount (-F).  */
static int optfork = 0;

/* Add volumelabel in a listing of mounted devices (-l). */
static int list_with_volumelabel = 0;

/* Nonzero for mount {--bind|--replace|--before|--after|--over|--move} */
static int mounttype = 0;

/* True if ruid != euid.  */
static int suid = 0;

/* Contains the fd to read the passphrase from, if any. */
static int pfd = -1;

/* Map from -o and fstab option strings to the flag argument to mount(2).  */
struct opt_map {
  const char *opt;		/* option name */
  int  skip;			/* skip in mtab option string */
  int  inv;			/* true if flag value should be inverted */
  int  mask;			/* flag mask value */
};

/* Custom mount options for our own purposes.  */
/* Maybe these should now be freed for kernel use again */
#define MS_NOAUTO	0x80000000
#define MS_USERS	0x40000000
#define MS_USER		0x20000000
#define MS_OWNER	0x10000000
#define MS_GROUP	0x08000000
#define MS_COMMENT	0x00020000
#define MS_LOOP		0x00010000

/* Options that we keep the mount system call from seeing.  */
#define MS_NOSYS	(MS_NOAUTO|MS_USERS|MS_USER|MS_COMMENT|MS_LOOP)

/* Options that we keep from appearing in the options field in the mtab.  */
#define MS_NOMTAB	(MS_REMOUNT|MS_NOAUTO|MS_USERS|MS_USER)

/* Options that we make ordinary users have by default.  */
#define MS_SECURE	(MS_NOEXEC|MS_NOSUID|MS_NODEV)

/* Options that we make owner-mounted devices have by default */
#define MS_OWNERSECURE	(MS_NOSUID|MS_NODEV)

static const struct opt_map opt_map[] = {
  { "defaults",	0, 0, 0		},	/* default options */
  { "ro",	1, 0, MS_RDONLY	},	/* read-only */
  { "rw",	1, 1, MS_RDONLY	},	/* read-write */
  { "exec",	0, 1, MS_NOEXEC	},	/* permit execution of binaries */
  { "noexec",	0, 0, MS_NOEXEC	},	/* don't execute binaries */
  { "suid",	0, 1, MS_NOSUID	},	/* honor suid executables */
  { "nosuid",	0, 0, MS_NOSUID	},	/* don't honor suid executables */
  { "dev",	0, 1, MS_NODEV	},	/* interpret device files  */
  { "nodev",	0, 0, MS_NODEV	},	/* don't interpret devices */
  { "sync",	0, 0, MS_SYNCHRONOUS},	/* synchronous I/O */
  { "async",	0, 1, MS_SYNCHRONOUS},	/* asynchronous I/O */
  { "dirsync",	0, 0, MS_DIRSYNC},	/* synchronous directory modifications */
  { "remount",  0, 0, MS_REMOUNT},      /* Alter flags of mounted FS */
  { "bind",	0, 0, MS_BIND   },	/* Remount part of tree elsewhere */
  { "rbind",	0, 0, MS_BIND|MS_REC }, /* Idem, plus mounted subtrees */
  { "auto",	0, 1, MS_NOAUTO	},	/* Can be mounted using -a */
  { "noauto",	0, 0, MS_NOAUTO	},	/* Can  only be mounted explicitly */
  { "users",	0, 0, MS_USERS	},	/* Allow ordinary user to mount */
  { "nousers",	0, 1, MS_USERS	},	/* Forbid ordinary user to mount */
  { "user",	0, 0, MS_USER	},	/* Allow ordinary user to mount */
  { "nouser",	0, 1, MS_USER	},	/* Forbid ordinary user to mount */
  { "owner",	0, 0, MS_OWNER  },	/* Let the owner of the device mount */
  { "noowner",	0, 1, MS_OWNER  },	/* Device owner has no special privs */
  { "group",	0, 0, MS_GROUP  },	/* Let the group of the device mount */
  { "nogroup",	0, 1, MS_GROUP  },	/* Device group has no special privs */
  { "_netdev",	0, 0, MS_COMMENT},	/* Device requires network */
  { "comment",	0, 0, MS_COMMENT},	/* fstab comment only (kudzu,_netdev)*/

  /* add new options here */
#ifdef MS_NOSUB
  { "sub",	0, 1, MS_NOSUB	},	/* allow submounts */
  { "nosub",	0, 0, MS_NOSUB	},	/* don't allow submounts */
#endif
#ifdef MS_SILENT
  { "quiet",	0, 0, MS_SILENT    },	/* be quiet  */
  { "loud",	0, 1, MS_SILENT    },	/* print out messages. */
#endif
#ifdef MS_MANDLOCK
  { "mand",	0, 0, MS_MANDLOCK },	/* Allow mandatory locks on this FS */
  { "nomand",	0, 1, MS_MANDLOCK },	/* Forbid mandatory locks on this FS */
#endif
  { "loop",	1, 0, MS_LOOP	},	/* use a loop device */
#ifdef MS_NOATIME
  { "atime",	0, 1, MS_NOATIME },	/* Update access time */
  { "noatime",	0, 0, MS_NOATIME },	/* Do not update access time */
#endif
#ifdef MS_NODIRATIME
  { "diratime",	0, 1, MS_NODIRATIME },	/* Update dir access times */
  { "nodiratime", 0, 0, MS_NODIRATIME },/* Do not update dir access times */
#endif
  { NULL,	0, 0, 0		}
};

static const char *opt_loopdev, *opt_vfstype, *opt_offset, *opt_encryption,
	*opt_speed, *opt_comment;

static struct string_opt_map {
  char *tag;
  int skip;
  const char **valptr;
} string_opt_map[] = {
  { "loop=",	0, &opt_loopdev },
  { "vfs=",	1, &opt_vfstype },
  { "offset=",	0, &opt_offset },
  { "encryption=", 0, &opt_encryption },
  { "speed=", 0, &opt_speed },
  { "comment=", 1, &opt_comment },
  { NULL, 0, NULL }
};

static void
clear_string_opts(void) {
	struct string_opt_map *m;

	for (m = &string_opt_map[0]; m->tag; m++)
		*(m->valptr) = NULL;
}

static int
parse_string_opt(char *s) {
	struct string_opt_map *m;
	int lth;

	for (m = &string_opt_map[0]; m->tag; m++) {
		lth = strlen(m->tag);
		if (!strncmp(s, m->tag, lth)) {
			*(m->valptr) = xstrdup(s + lth);
			return 1;
		}
	}
	return 0;
}

int mount_quiet=0;

/* Report on a single mount.  */
static void
print_one (const struct my_mntent *me) {
	if (mount_quiet)
		return;
	printf ("%s on %s", me->mnt_fsname, me->mnt_dir);
	if (me->mnt_type != NULL && *(me->mnt_type) != '\0')
		printf (" type %s", me->mnt_type);
	if (me->mnt_opts != NULL)
		printf (" (%s)", me->mnt_opts);
	if (list_with_volumelabel) {
		const char *label;
		label = mount_get_volume_label_by_spec(me->mnt_fsname);
		if (label) {
			printf (" [%s]", label);
			/* free(label); */
		}
	}
	printf ("\n");
}

/* Report on everything in mtab (of the specified types if any).  */
static int
print_all (char *types) {
     struct mntentchn *mc, *mc0;

     mc0 = mtab_head();
     for (mc = mc0->nxt; mc && mc != mc0; mc = mc->nxt) {
	  if (matching_type (mc->m.mnt_type, types))
	       print_one (&(mc->m));
     }
     exit (0);
}

static void
my_free(const void *s) {
	if (s)
		free((void *) s);
}

/*
 * Look for OPT in opt_map table and return mask value.
 * If OPT isn't found, tack it onto extra_opts (which is non-NULL).
 * For the options uid= and gid= replace user or group name by its value.
 */
static inline void
parse_opt (const char *opt, int *mask, char *extra_opts) {
	const struct opt_map *om;

	for (om = opt_map; om->opt != NULL; om++)
		if (streq (opt, om->opt)) {
			if (om->inv)
				*mask &= ~om->mask;
			else
				*mask |= om->mask;
			if ((om->mask == MS_USER || om->mask == MS_USERS)
			    && !om->inv)
				*mask |= MS_SECURE;
			if ((om->mask == MS_OWNER || om->mask == MS_GROUP)
			    && !om->inv)
				*mask |= MS_OWNERSECURE;
#ifdef MS_SILENT
			if (om->mask == MS_SILENT && om->inv)  {
				mount_quiet = 1;
				verbose = 0;
			}
#endif
			return;
		}

	if (*extra_opts)
		strcat(extra_opts, ",");

	/* convert nonnumeric ids to numeric */
	if (!strncmp(opt, "uid=", 4) && !isdigit(opt[4])) {
		struct passwd *pw = getpwnam(opt+4);
		char uidbuf[20];

		if (pw) {
			sprintf(uidbuf, "uid=%d", pw->pw_uid);
			strcat(extra_opts, uidbuf);
			return;
		}
	}
	if (!strncmp(opt, "gid=", 4) && !isdigit(opt[4])) {
		struct group *gr = getgrnam(opt+4);
		char gidbuf[20];

		if (gr) {
			sprintf(gidbuf, "gid=%d", gr->gr_gid);
			strcat(extra_opts, gidbuf);
			return;
		}
	}

	strcat(extra_opts, opt);
}
  
/* Take -o options list and compute 4th and 5th args to mount(2).  flags
   gets the standard options (indicated by bits) and extra_opts all the rest */
static void
parse_opts (const char *options, int *flags, char **extra_opts) {
	*flags = 0;
	*extra_opts = NULL;

	clear_string_opts();

	if (options != NULL) {
		char *opts = xstrdup(options);
		char *opt;

		*extra_opts = xmalloc (strlen (opts) + 1); 
		**extra_opts = '\0';

		for (opt = strtok (opts, ","); opt; opt = strtok (NULL, ","))
			if (!parse_string_opt (opt))
				parse_opt (opt, flags, *extra_opts);

		free(opts);
	}

	if (readonly)
		*flags |= MS_RDONLY;
	if (readwrite)
		*flags &= ~MS_RDONLY;
	*flags |= mounttype;
}

/* Try to build a canonical options string.  */
static char *
fix_opts_string (int flags, const char *extra_opts, const char *user) {
	const struct opt_map *om;
	const struct string_opt_map *m;
	char *new_opts;

	new_opts = xstrdup((flags & MS_RDONLY) ? "ro" : "rw");
	for (om = opt_map; om->opt != NULL; om++) {
		if (om->skip)
			continue;
		if (om->inv || !om->mask || (flags & om->mask) != om->mask)
			continue;
		new_opts = xstrconcat3(new_opts, ",", om->opt);
		flags &= ~om->mask;
	}
	for (m = &string_opt_map[0]; m->tag; m++) {
		if (!m->skip && *(m->valptr))
			new_opts = xstrconcat4(new_opts, ",",
					       m->tag, *(m->valptr));
	}
	if (extra_opts && *extra_opts) {
		new_opts = xstrconcat3(new_opts, ",", extra_opts);
	}
	if (user) {
		new_opts = xstrconcat3(new_opts, ",user=", user);
	}
	return new_opts;
}

static int
already (const char *spec, const char *node) {
	struct mntentchn *mc;
	int ret = 1;

	if ((mc = getmntfile(node)) != NULL)
		error (_("mount: according to mtab, "
			 "%s is already mounted on %s"),
		       mc->m.mnt_fsname, node);
	else if (spec && strcmp (spec, "none") &&
		 (mc = getmntfile(spec)) != NULL)
		error (_("mount: according to mtab, %s is mounted on %s"),
		       spec, mc->m.mnt_dir);
	else
		ret = 0;
	return ret;
}

/* Create mtab with a root entry.  */
static void
create_mtab (void) {
	struct mntentchn *fstab;
	struct my_mntent mnt;
	int flags;
	mntFILE *mfp;

	lock_mtab();

	mfp = my_setmntent (MOUNTED, "a+");
	if (mfp == NULL || mfp->mntent_fp == NULL) {
		int errsv = errno;
		die (EX_FILEIO, _("mount: can't open %s for writing: %s"),
		     MOUNTED, strerror (errsv));
	}

	/* Find the root entry by looking it up in fstab */
	if ((fstab = getfsfile ("/")) || (fstab = getfsfile ("root"))) {
		char *extra_opts;
		parse_opts (fstab->m.mnt_opts, &flags, &extra_opts);
		mnt.mnt_dir = "/";
		mnt.mnt_fsname = canonicalize (fstab->m.mnt_fsname);
		mnt.mnt_type = fstab->m.mnt_type;
		mnt.mnt_opts = fix_opts_string (flags, extra_opts, NULL);
		mnt.mnt_freq = mnt.mnt_passno = 0;
		my_free(extra_opts);

		if (my_addmntent (mfp, &mnt) == 1) {
			int errsv = errno;
			die (EX_FILEIO, _("mount: error writing %s: %s"),
			     MOUNTED, strerror (errsv));
		}
	}
	if (fchmod (fileno (mfp->mntent_fp), 0644) < 0)
		if (errno != EROFS) {
			int errsv = errno;
			die (EX_FILEIO,
			     _("mount: error changing mode of %s: %s"),
			     MOUNTED, strerror (errsv));
		}
	my_endmntent (mfp);

	unlock_mtab();
}

/* count successful mount system calls */
static int mountcount = 0;

/*
 * do_mount_syscall()
 *	Mount a single file system. Keep track of successes.
 * returns: 0: OK, -1: error in errno
 */
static int
do_mount_syscall (struct mountargs *args) {
	int flags = args->flags;
	int ret;

	if ((flags & MS_MGC_MSK) == 0)
		flags |= MS_MGC_VAL;

	ret = mount (args->spec, args->node, args->type, flags, args->data);
	if (ret == 0)
		mountcount++;
	return ret;
}

/*
 * guess_fstype_and_mount()
 *	Mount a single file system. Guess the type when unknown.
 * returns: 0: OK, -1: error in errno, 1: other error
 *	don't exit on non-fatal errors.
 *	on return types is filled with the type used.
 */
static int
guess_fstype_and_mount(const char *spec, const char *node, const char **types,
		       int flags, char *mount_opts) {
   struct mountargs args = { spec, node, NULL, flags & ~MS_NOSYS, mount_opts };
   
   if (*types && strcasecmp (*types, "auto") == 0)
      *types = NULL;

   if (!*types && (flags & (MS_BIND | MS_MOVE)))
      *types = "none";		/* random, but not "bind" */

   if (!*types && !(flags & MS_REMOUNT)) {
      *types = guess_fstype(spec);
      if (*types && !strcmp(*types, "swap")) {
	  error(_("%s looks like swapspace - not mounted"), spec);
	  *types = NULL;
	  return 1;
      }
   }

   /* Accept a comma-separated list of types, and try them one by one */
   /* A list like "nonfs,.." indicates types not to use */
   if (*types && strncmp(*types, "no", 2) && index(*types,',')) {
      char *t = strdup(*types);
      char *p;

      while((p = index(t,',')) != NULL) {
	 *p = 0;
	 args.type = *types = t;
	 if(do_mount_syscall (&args) == 0)
	    return 0;
	 t = p+1;
      }
      /* do last type below */
      *types = t;
   }

   if (*types || (flags & MS_REMOUNT)) {
      args.type = *types;
      return do_mount_syscall (&args);
   }

   return procfsloop(do_mount_syscall, &args, types);
}

/*
 * suid_check()
 *	Die if the user is not allowed to do this.
 */
static void
suid_check(const char *spec, const char *node, int *flags, char **user) {
  if (suid) {
      /*
       * MS_OWNER: Allow owners to mount when fstab contains
       * the owner option.  Note that this should never be used
       * in a high security environment, but may be useful to give
       * people at the console the possibility of mounting a floppy.
       * MS_GROUP: Allow members of device group to mount. (Martin Dickopp)
       */
      if (*flags & (MS_OWNER | MS_GROUP)) {
	  struct stat sb;

	  if (!strncmp(spec, "/dev/", 5) && stat(spec, &sb) == 0) {

	      if (*flags & MS_OWNER) {
		  if (getuid() == sb.st_uid)
		      *flags |= MS_USER;
	      }

	      if (*flags & MS_GROUP) {
		  if (getgid() == sb.st_gid)
		      *flags |= MS_USER;
		  else {
		      int n = getgroups(0, NULL);

		      if (n > 0) {
			      gid_t *groups = xmalloc(n * sizeof(*groups));
			      if (getgroups(n, groups) == n) {
				      int i;
				      for (i = 0; i < n; i++) {
					      if (groups[i] == sb.st_gid) {
						      *flags |= MS_USER;
						      break;
					      }
				      }
			      }
			      free(groups);
		      }
		  }
	      }
	  }
      }

      /* James Kehl <[e-mail]> came with a similar patch:
	 allow an arbitrary user to mount when he is the owner of
	 the mount-point and has write-access to the device.
	 This is even less secure. Let me skip it for the time being;
	 there should be an explicit fstab line allowing such things. */

      if (!(*flags & (MS_USER | MS_USERS))) {
	  if (already (spec, node))
	    die (EX_USAGE, _("mount failed"));
	  else
	    die (EX_USAGE, _("mount: only root can mount %s on %s"), spec, node);
      }
      if (*flags & MS_USER)