mount: support user mounts if CONFIG_DESKTOP

include/applets.h

@@ -46,6 +46,10 @@
 # define _BB_DIR_USR_SBIN _BB_DIR_SBIN
 #endif
 
+// _BB_SUID_ALWAYS: will complain if busybox isn't suid
+// and is run by non-root (applet_main() will not be called at all)
+// _BB_SUID_NEVER: will drop suid prior to applet_main()
+// _BB_SUID_MAYBE: neither of the above
 
 USE_TEST(APPLET_NOUSAGE([, test, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
 USE_TEST(APPLET_NOUSAGE([[, test, _BB_DIR_USR_BIN, _BB_SUID_NEVER))
@@ -198,7 +202,7 @@ USE_MKSWAP(APPLET(mkswap, _BB_DIR_SBIN, _BB_SUID_NEVER))
 USE_MKTEMP(APPLET(mktemp, _BB_DIR_BIN, _BB_SUID_NEVER))
 USE_MODPROBE(APPLET(modprobe, _BB_DIR_SBIN, _BB_SUID_NEVER))
 USE_MORE(APPLET(more, _BB_DIR_BIN, _BB_SUID_NEVER))
-USE_MOUNT(APPLET(mount, _BB_DIR_BIN, _BB_SUID_NEVER))
+USE_MOUNT(APPLET(mount, _BB_DIR_BIN, USE_DESKTOP(_BB_SUID_MAYBE) SKIP_DESKTOP(_BB_SUID_NEVER)))
 USE_MOUNTPOINT(APPLET(mountpoint, _BB_DIR_BIN, _BB_SUID_NEVER))
 USE_MSH(APPLET_NOUSAGE(msh, msh, _BB_DIR_BIN, _BB_SUID_NEVER))
 USE_MT(APPLET(mt, _BB_DIR_BIN, _BB_SUID_NEVER))

util-linux/mount.c

@@ -32,8 +32,19 @@
 
 
 // Not real flags, but we want to be able to check for this.
-#define MOUNT_NOAUTO    (1<<29)
+enum {
-#define MOUNT_SWAP      (1<<30)
+	MOUNT_USERS  = (1<<28)*ENABLE_DESKTOP,
+	MOUNT_NOAUTO = (1<<29),
+	MOUNT_SWAP   = (1<<30),
+};
+// TODO: more "user" flag compatibility.
+// "user" option (from mount manpage):
+// Only the user that mounted a filesystem can unmount it again.
+// If any user should be able to unmount, then use users instead of user
+// in the fstab line.  The owner option is similar to the user option,
+// with the restriction that the user must be the owner of the special file.
+// This may be useful e.g. for /dev/fd if a login script makes
+// the console user owner of this device.
 
 /* Standard mount options (from -o options or --options), with corresponding
  * flags */
@@ -53,6 +64,8 @@ struct {
 		{"quiet", 0},
 		{"noauto", MOUNT_NOAUTO},
 		{"swap", MOUNT_SWAP},
+		USE_DESKTOP({"user",  MOUNT_USERS},)
+		USE_DESKTOP({"users", MOUNT_USERS},)
 	)
 
 	USE_FEATURE_MOUNT_FLAGS(
@@ -106,7 +119,8 @@ static void append_mount_options(char **oldopts, char *newopts)
 			if (p) len = p - newopts;
 			p = *oldopts;
 			while (1) {
-				if (!strncmp(p,newopts,len) && (p[len]==',' || p[len]==0))
+				if (!strncmp(p, newopts, len)
+				 && (p[len]==',' || p[len]==0))
 					goto skip;
 				p = strchr(p,',');
 				if(!p) break;
@@ -1422,6 +1436,8 @@ report_error:
 // Parse options, if necessary parse fstab/mtab, and call singlemount for
 // each directory to be mounted.
 
+const char must_be_root[] = "you must be root";
+
 int mount_main(int argc, char **argv)
 {
 	enum { OPT_ALL = 0x10 };
@@ -1433,6 +1449,8 @@ int mount_main(int argc, char **argv)
 	int i, j, rc = 0;
 	unsigned opt;
 	struct mntent mtpair[2], *mtcur = mtpair;
+	SKIP_DESKTOP(const int nonroot = 0;)
+	USE_DESKTOP( int nonroot = (getuid() != 0);)
 
 	/* parse long options, like --bind and --move.  Note that -o option
 	 * and --option are synonymous.  Yes, this means --remount,rw works. */
@@ -1475,7 +1493,7 @@ int mount_main(int argc, char **argv)
 			while (getmntent_r(mountTable, mtpair, bb_common_bufsiz1,
 								sizeof(bb_common_bufsiz1)))
 			{
-				// Don't show rootfs.
+				// Don't show rootfs. FIXME: why??
 				if (!strcmp(mtpair->mnt_fsname, "rootfs")) continue;
 
 				if (!fstype || !strcmp(mtpair->mnt_type, fstype))
@@ -1493,6 +1511,8 @@ int mount_main(int argc, char **argv)
 	// argument when we get it.
 
 	if (argc == 2) {
+		if (nonroot)
+			bb_error_msg_and_die(must_be_root);
 		mtpair->mnt_fsname = argv[0];
 		mtpair->mnt_dir = argv[1];
 		mtpair->mnt_type = fstype;
@@ -1502,6 +1522,8 @@ int mount_main(int argc, char **argv)
 	}
 
 	i = parse_mount_options(cmdopts, 0);
+	if (nonroot && (i & ~MS_SILENT)) // Non-root users cannot specify flags
+		bb_error_msg_and_die(must_be_root);
 
 	// If we have a shared subtree flag, don't worry about fstab or mtab.
 
@@ -1515,9 +1537,10 @@ int mount_main(int argc, char **argv)
 
 	// Open either fstab or mtab
 
-	if (i & MS_REMOUNT)
+	fstabname = "/etc/fstab";
+	if (i & MS_REMOUNT) {
 		fstabname = bb_path_mtab_file;
-	else fstabname = "/etc/fstab";
+	}
 	fstab = setmntent(fstabname, "r");
 	if (!fstab)
 		bb_perror_msg_and_die("cannot read %s", fstabname);
@@ -1544,9 +1567,15 @@ int mount_main(int argc, char **argv)
 					bb_error_msg_and_die("can't find %s in %s",
 						argv[0], fstabname);
 
+				mtcur = mtnext;
+				if (nonroot) {
+					// fstab must have "users" or "user"
+					if (!(parse_mount_options(mtcur->mnt_opts, 0) & MOUNT_USERS))
+						bb_error_msg_and_die(must_be_root);
+				}
+
 				// Mount the last thing we found.
 
-				mtcur = mtnext;
 				mtcur->mnt_opts = xstrdup(mtcur->mnt_opts);
 				append_mount_options(&(mtcur->mnt_opts), cmdopts);
 				rc = singlemount(mtcur, 0);
@@ -1576,8 +1605,9 @@ int mount_main(int argc, char **argv)
 		// If we're mounting all.
 
 		} else {
-
 			// Do we need to match a filesystem type?
+			// TODO: support "-t type1,type2"; "-t notype1,type2"
+
 			if (fstype && strcmp(mtcur->mnt_type, fstype)) continue;
 
 			// Skip noauto and swap anyway.
@@ -1585,6 +1615,12 @@ int mount_main(int argc, char **argv)
 			if (parse_mount_options(mtcur->mnt_opts, 0)
 				& (MOUNT_NOAUTO | MOUNT_SWAP)) continue;
 
+			// No, mount -a won't mount anything,
+			// even user mounts, for mere humans.
+
+			if (nonroot)
+				bb_error_msg_and_die(must_be_root);
+
 			// Mount this thing.
 
 			if (singlemount(mtcur, 1)) {