Merge illumos-gate

[unleashed.git] / usr / src / cmd / rmvolmgr / vold.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * Vold compatibility for rmvolmgr: emulate old commands as well as
 * action_filemgr.so to notify legacy apps via /tmp/.removable pipes.
 * A lot of this code is copied verbatim from vold sources.
 *
 * Here's the original description of action_filemgr.so:
 *
 * action_filemgr.so - filemgr interface routines for rmmount
 *
 * This shared object allows rmmount to communicate with filemgr.
 * This is done by communicating over a named pipe that filemgr
 * creates in directory NOTIFY_DIR.  The name of the pipe must
 * begin with NOTIFY_NAME.  This source file contains #define
 * compiler directives set the values of NOTIFY_DIR and NOTIFY_NAME.
 *
 * After a partition on a medium has been mounted as a result of
 * either insertion or remounting of the medium, the action()
 * method creates a file named with the symbolic name of the
 * device in which the medium is inserted and the partition name
 * (e.g. "jaz0-s2") in NOTIFY_DIR.  The file consists of one text
 * line containing a string naming the mount point of the partition,
 * a string giving the raw device path to the partition, and a
 * string naming the file system type on the partition.  The action()
 * method then sends a single character ('i' for insertion, 'r' for
 * remounting) through the named pipe NOTIFY_NAME to tell filemgr to
 * look for new files in NOTIFY_DIR.
 *
 * If a medium containing no mountable partitions is inserted
 * or remounted in a device, the action() method creates a file
 * named with the symbolic name of the device in NOTIFY_DIR.
 * The file consists of one text line containing a string
 * giving the symbolic name of the device and a string naming
 * the reason that the medium couldn't be mounted.  The action
 * method then sends either an 'i' or an 'r' through the named
 * pipe to tell filemgr to look for new files in NOTIFY_DIR.
 *
 * When a medium is ejected or unmounted, the action() method
 * removes the files that were created in NOTIFY_DIR when the medium
 * was inserted or remounted and sends a single character ('e' for
 * ejection, 'u' for unmounting) through the named pipe.
 *
 * The following environment variables must be set before calling action():
 *
 *      VOLUME_ACTION           action that occurred (e.g. "insert", "eject")
 *      VOLUME_SYMDEV           symbolic name (e.g. "cdrom0", "floppy1")
 *      VOLUME_NAME             volume name (e.g. "unnamed_cdrom", "s2")
 */


#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <strings.h>
#include <dirent.h>
#include <signal.h>
#include <errno.h>
#include <libintl.h>
#include <zone.h>
#include <pwd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/dkio.h>
#include <sys/cdio.h>
#include <sys/vtoc.h>
#include <sys/param.h>
#include <sys/wait.h>
#include <libcontract.h>
#include <sys/contract/process.h>
#include <sys/ctfs.h>

#include "vold.h"
#include "rmm_common.h"

int             rmm_debug = 0;
boolean_t       rmm_vold_actions_enabled = B_FALSE;
boolean_t       rmm_vold_mountpoints_enabled = B_FALSE;

static char     *prog_name = NULL;
static pid_t    prog_pid = 0;
static uid_t    mnt_uid = (uid_t)-1;
static gid_t    mnt_gid = (gid_t)-1;
static zoneid_t mnt_zoneid = -1;
static char     mnt_zoneroot[MAXPATHLEN];
static char     mnt_userdir[MAXPATHLEN];

/*
 * Private attribute types and attributes.
 */
static const char notify_characters[] = {
        'e',
        'i',
        'r',
        'u'
};

static const char *result_strings[] = {
        "FALSE",
        "TRUE"
};

#define NOTIFY_DIR      "/tmp/.removable"       /* dir where filemgr looks */
#define NOTIFY_NAME     "notify"                /* named pipe to talk over */

static void     volrmmount_usage();
static void     volcheck_usage();
static int      vold_action(struct action_arg *aap);
static void     vold_update_mountpoints(struct action_arg *aap);
static char     *not_mountable(struct action_arg *aa);
static int      create_one_notify_file(char *fstype,
                                char *mount_point,
                                char *notify_file,
                                char *raw_partitionp,
                                char *reason,
                                char *symdev);
static int      create_notify_files(struct action_arg **aa);
static boolean_t notify_clients(action_t action, int do_notify);
static void     popdir(int fd);
static int      pushdir(const char *dir);
static boolean_t remove_notify_files(struct action_arg **aa);

/*
 * Old version of rmmount(8)
 */
/* ARGSUSED */
int
vold_rmmount(int argc, char **argv)
{
        char            *volume_action;
        char            *volume_mediatype;
        char            *volume_mount_mode;
        char            *volume_name;
        char            *volume_path;
        char            *volume_pcfs_id;
        char            *volume_symdev;
        char            *volume_zonename;
        char            *volume_user;
        action_t        action;
        char            mountpoint[MAXPATHLEN];
        char            *zonemountpoint;
        char            *arg_mountpoint = NULL;
        LibHalContext   *hal_ctx;
        DBusError       error;
        rmm_error_t     rmm_error;
        int             ret;

        prog_name = argv[0];
        prog_pid = getpid();

        mnt_zoneroot[0] = '\0';
        mnt_userdir[0] = '\0';

        volume_action = getenv("VOLUME_ACTION");
        volume_mediatype = getenv("VOLUME_MEDIATYPE");
        volume_mount_mode = getenv("VOLUME_MOUNT_MODE");
        volume_name = getenv("VOLUME_NAME");
        volume_path = getenv("VOLUME_PATH");
        volume_pcfs_id = getenv("VOLUME_PCFS_ID");
        volume_symdev = getenv("VOLUME_SYMDEV");

        if (volume_action == NULL) {
                dprintf("%s(%ld): VOLUME_ACTION was null!!\n",
                    prog_name, prog_pid);
                return (-1);
        }
        if (volume_mediatype == NULL) {
                dprintf("%s(%ld): VOLUME_MEDIATYPE was null!!\n",
                    prog_name, prog_pid);
                return (-1);
        }
        if (volume_mount_mode == NULL) {
                volume_mount_mode = "rw";
        }
        if (volume_name == NULL) {
                dprintf("%s(%ld): VOLUME_NAME was null!!\n",
                    prog_name, prog_pid);
                return (-1);
        }
        if (volume_path == NULL) {
                dprintf("%s(%ld): VOLUME_PATH was null!!\n",
                    prog_name, prog_pid);
                return (-1);
        }
        if (volume_pcfs_id == NULL) {
                volume_pcfs_id = "";
        }
        if (volume_symdev == NULL) {
                dprintf("%s(%ld): VOLUME_SYMDEV was null!!\n",
                    prog_name, prog_pid);
                return (-1);
        }

        rmm_vold_mountpoints_enabled = B_TRUE;
        rmm_vold_actions_enabled = B_TRUE;

        if ((hal_ctx = rmm_hal_init(0, 0, 0, 0, &error, &rmm_error)) == NULL) {
                rmm_dbus_error_free(&error);

                /* if HAL's not running, must be root */
                if (geteuid() != 0) {
                        (void) fprintf(stderr,
                            gettext("%s(%ld) error: must be root to execute\n"),
                            prog_name, prog_pid);
                        return (-1);
                }
        }

        if (strcmp(volume_action, "eject") == 0) {
                action = EJECT;
        } else if (strcmp(volume_action, "insert") == 0) {
                action = INSERT;
        } else if (strcmp(volume_action, "remount") == 0) {
                action = REMOUNT;
        } else if (strcmp(volume_action, "unmount") == 0) {
                action = UNMOUNT;
        }

        ret = rmm_action(hal_ctx, volume_symdev, action, 0, 0, 0,
            arg_mountpoint) ? 0 : 1;

        if (hal_ctx != NULL) {
                rmm_hal_fini(hal_ctx);
        }

        return (ret);
}


/*
 * this should be called after rmm_hal_{mount,unmount,eject}
 */
int
vold_postprocess(LibHalContext *hal_ctx, const char *udi,
    struct action_arg *aap)
{
        int     ret = 0;

        /* valid mountpoint required */
        if ((aap->aa_action == INSERT) || (aap->aa_action == REMOUNT)) {
                rmm_volume_aa_update_mountpoint(hal_ctx, udi, aap);
                if ((aap->aa_mountpoint == NULL) ||
                    (strlen(aap->aa_mountpoint) == 0)) {
                        return (1);
                }
        }

        if (rmm_vold_mountpoints_enabled) {
                vold_update_mountpoints(aap);
        }
        if (rmm_vold_actions_enabled) {
                ret = vold_action(aap);
        }

        return (ret);
}

/*
 * update legacy symlinks
 *
 * For cdrom:
 *
 *      /cdrom/<name> -> original mountpoint
 *      /cdrom/cdrom0 -> ./<name>
 *      /cdrom/cdrom -> cdrom0  (only for cdrom0)
 *
 * If it's a slice or partition, /cdrom/<name> becomes a directory:
 *
 *      /cdrom/<name>/s0
 *
 * Same for rmdisk and floppy.
 */
static void
vold_update_mountpoints(struct action_arg *aap)
{
        boolean_t       is_partition;
        char            part_dir[2 * MAXNAMELEN];
        char            symname_mp[2 * MAXNAMELEN];
        char            symcontents_mp[MAXNAMELEN];
        char            symname[2 * MAXNAMELEN];
        char            symcontents[MAXNAMELEN];

        is_partition = (aap->aa_partname != NULL);

        if (!is_partition) {
                /* /cdrom/<name> -> original mountpoint */
                (void) snprintf(symcontents_mp, sizeof (symcontents_mp),
                    "%s", aap->aa_mountpoint);
                (void) snprintf(symname_mp, sizeof (symname_mp),
                    "/%s/%s", aap->aa_media, aap->aa_name);
        } else {
                /* /cdrom/<name>/slice -> original mountpoint */
                (void) snprintf(part_dir, sizeof (part_dir),
                    "/%s/%s", aap->aa_media, aap->aa_name);
                (void) snprintf(symcontents_mp, sizeof (symcontents_mp),
                    "%s", aap->aa_mountpoint);
                (void) snprintf(symname_mp, sizeof (symname_mp),
                    "/%s/%s/%s", aap->aa_media, aap->aa_name,
                    aap->aa_partname);

        }
        /* /cdrom/cdrom0 -> ./<name> */
        (void) snprintf(symcontents, sizeof (symcontents),
            "./%s", aap->aa_name);
        (void) snprintf(symname, sizeof (symname),
            "/%s/%s", aap->aa_media, aap->aa_symdev);

        (void) unlink(symname);
        (void) unlink(symname_mp);
        if (is_partition) {
                (void) rmdir(part_dir);
        }

        if ((aap->aa_action == INSERT) || (aap->aa_action == REMOUNT)) {
                (void) mkdir(aap->aa_media, 0755);
                if (is_partition) {
                        (void) mkdir(part_dir, 0755);
                }
                (void) symlink(symcontents_mp, symname_mp);
                (void) symlink(symcontents, symname);
        }
}


static int
vold_action(struct action_arg *aap)
{
        action_t        action;
        int             result;
        int             do_notify = FALSE;
        action_t        notify_act = EJECT;
        struct action_arg *aa[2];
        struct action_arg a1;

        dprintf("%s[%d]: entering action()\n", __FILE__, __LINE__);

        if (mnt_zoneid > GLOBAL_ZONEID) {
                pid_t   pid;
                int     status;
                int     ifx;
                int     tmpl_fd;
                int     err = 0;

                tmpl_fd = open(CTFS_ROOT "/process/template",
                    O_RDWR);
                if (tmpl_fd == -1)
                        return (1);

                /*
                 * Deliver no events, don't inherit,
                 * and allow it to be orphaned.
                 */
                err |= ct_tmpl_set_critical(tmpl_fd, 0);
                err |= ct_tmpl_set_informative(tmpl_fd, 0);
                err |= ct_pr_tmpl_set_fatal(tmpl_fd,
                    CT_PR_EV_HWERR);
                err |= ct_pr_tmpl_set_param(tmpl_fd,
                    CT_PR_PGRPONLY |
                    CT_PR_REGENT);
                if (err || ct_tmpl_activate(tmpl_fd)) {
                        (void) close(tmpl_fd);
                        return (1);
                }
                switch (pid = fork1()) {
                case 0:
                        (void) ct_tmpl_clear(tmpl_fd);
                        for (ifx = 0; ifx < _NFILE; ifx++)
                                (void) close(ifx);

                        if (zone_enter(mnt_zoneid) == -1)
                                _exit(0);

                        /* entered zone, proceed to action */
                        break;
                case -1:
                        dprintf("fork1 failed \n ");
                        return (1);
                default :
                        (void) ct_tmpl_clear(tmpl_fd);
                        (void) close(tmpl_fd);
                        if (waitpid(pid, &status, 0) < 0) {
                                dprintf("%s(%ld): waitpid() "
                                    "failed (errno %d) \n",
                                    prog_name, prog_pid, errno);
                                return (1);
                        }
                }
        }

        /* only support one action at a time XXX */
        a1.aa_path = NULL;
        aa[0] = aap;
        aa[1] = &a1;

        action = aa[0]->aa_action;

        if (action == CLEAR_MOUNTS) {
                /*
                 * Remove the notifications files, but don't
                 * notify the client.  The "clear_mounts" action
                 * simply clears all existing mounts of a medium's
                 * partitions after a medium has been repartitioned.
                 * Then vold builds a new file system that reflects
                 * the medium's new partition structure and mounts
                 * the new partitions by calling rmmount, and therefore
                 * action(), with the VOLUME_ACTION environment variable
                 * set to "remount".
                 */
                result = remove_notify_files(aa);
                result = TRUE;
        } else if (action == EJECT) {
                result = remove_notify_files(aa);
                if (result == TRUE) {
                        do_notify = TRUE;
                        notify_act = EJECT;
                }
        } else if (action = INSERT) {
                result = create_notify_files(aa);
                if (result == TRUE) {
                        do_notify = TRUE;
                        notify_act = INSERT;
                }
        } else if (action == REMOUNT) {
                result = create_notify_files(aa);
                if (result == TRUE) {
                        do_notify = TRUE;
                        notify_act = REMOUNT;
                }
        } else if (action == UNMOUNT) {
                result = remove_notify_files(aa);
                if (result == TRUE) {
                        do_notify = TRUE;
                        notify_act = UNMOUNT;
                }
        } else {
                dprintf("%s[%d]: action(): invalid action: %s\n",
                    __FILE__, __LINE__, action);
                result = FALSE;
        }

        if (result == TRUE) {
                result = notify_clients(notify_act, do_notify);
        }

        dprintf("%s[%d]: leaving action(), result = %s\n",
            __FILE__, __LINE__, result_strings[result]);

        if (mnt_zoneid > GLOBAL_ZONEID) {
                /* exit forked local zone process */
                _exit(0);
        }

        if (result == TRUE) {
                /*
                 * File Manager is running. return 0.
                 * see man page rmmount.conf(4).
                 */
                return (0);
        } else {
                return (1);
        }
}


/*
 * Returns NULL if a medium or partition is mountable
 * and a string stating the reason the medium or partition
 * can't be mounted if the medium or partition isn't mountable.
 *
 * If the volume_name of the medium or partition is one of the
 * following, the medium or partition isn't mountable.
 *
 * unlabeled_<media_type>
 * unknown_format
 * password_protected
 */
/* ARGSUSED */
static char *
not_mountable(struct action_arg *aa)
{
        return (NULL);
}

static int
create_notify_files(struct action_arg **aa)
{
        int     ai;
        char    *fstype;
        char    *mount_point;
        char    notify_file[64];
        char    *raw_partitionp;
        char    *reason; /* Why the medium wasn't mounted */
        int     result;
        char    *symdev;

        dprintf("%s[%d]: entering create_notify_files()\n", __FILE__, __LINE__);

        ai = 0;
        result = FALSE;
        symdev = aa[ai]->aa_symdev;
        while ((aa[ai] != NULL) && (aa[ai]->aa_path != NULL)) {
                if (aa[ai]->aa_mountpoint != NULL) {
                        if (aa[ai]->aa_type) {
                                fstype = aa[ai]->aa_type;
                        } else {
                                fstype = "unknown";
                        }
                        mount_point = aa[ai]->aa_mountpoint;
                        if (aa[ai]->aa_partname != NULL) {
                                /*
                                 * Is aa_partname ever NULL?
                                 * When time permits, check.
                                 * If it is, the action taken
                                 * in the else clause could produce
                                 * file name conflicts.
                                 */
                                sprintf(notify_file, "%s-%s", symdev,
                                    aa[ai]->aa_partname);
                        } else {
                                sprintf(notify_file, "%s-0", symdev);
                        }
                        reason = NULL;
                } else {
                        /*
                         * The partition isn't mounted.
                         */
                        fstype = "none";
                        mount_point = "none";
                        reason = not_mountable(aa[ai]);
                        if (reason != NULL) {
                                sprintf(notify_file, "%s-0", symdev);
                        } else {
                                /*
                                 * Either the partition is a backup slice, or
                                 * rmmount tried to mount the partition, but
                                 * idenf_fs couldn't identify the file system
                                 * type; that can occur when rmmount is
                                 * trying to mount all the slices in a Solaris
                                 * VTOC, and one or more partitions don't have
                                 * file systems in them.
                                 */
                                if (aa[0]->aa_partname != NULL) {
                                        /*
                                         * Is aa_partname ever NULL?
                                         * When time permits, check.
                                         * If it is, the action taken
                                         * in the else clause could produce
                                         * file name conflicts.
                                         */
                                        sprintf(notify_file, "%s-%s", symdev,
                                            aa[0]->aa_partname);
                                } else {
                                        sprintf(notify_file, "%s-0", symdev);
                                }
                                if ((aa[0]->aa_type != NULL) &&
                                    (strcmp(aa[0]->aa_type, "backup_slice")
                                    == 0)) {
                                        reason = "backup_slice";
                                } else {
                                        reason = "unformatted_media";
                                }
                                /*
                                 * "unformatted_media" should be
                                 * changed to "unformmated_medium" for
                                 * grammatical correctness, but
                                 * "unformatted_media" is now specified
                                 * in the interface to filemgr, so the
                                 * change can't be made without the
                                 * approval of the CDE group.
                                 */
                        }
                }
                raw_partitionp = aa[0]->aa_rawpath;
                result = create_one_notify_file(fstype,
                    mount_point,
                    notify_file,
                    raw_partitionp,
                    reason,
                    symdev);
                ai++;
        }
        dprintf("%s[%d]: leaving create_notify_files(), result = %s\n",
            __FILE__, __LINE__, result_strings[result]);
        return (result);
}

static int
create_one_notify_file(char *fstype,
        char *mount_point,
        char *notify_file,
        char *raw_partitionp,
        char *reason,
        char *symdev)
{
        /*
         * For a mounted partition, create a notification file
         * indicating the mount point,  the raw device pathname
         * of the partition, and the partition's file system
         * type.  For an unmounted partition, create a
         * notification file containing the reason that the
         * partition wasn't mounted and the raw device pathname
         * of the partition.
         *
         * Create the file as root in a world-writable
         * directory that resides in a world-writable directory.
         *
         * Handle two possible race conditions that could
         * allow security breaches.
         */

        int     current_working_dir_fd;
        int     file_descriptor;
        FILE    *filep;
        int     result;

        dprintf("%s[%d]:Entering create_one_notify_file()\n",
            __FILE__, __LINE__);
        dprintf("\tcreate_one_notify_file(): fstype = %s\n", fstype);
        dprintf("\tcreate_one_notify_file(): mount_point = %s\n", mount_point);
        dprintf("\tcreate_one_notify_file(): notify_file = %s\n", notify_file);
        dprintf("\tcreate_one_notify_file(): raw_partitionp = %s\n",
            raw_partitionp);
        if (reason != NULL) {
                dprintf("\tcreate_one_notify_file(): reason = %s\n", reason);
        } else {
                dprintf("\tcreate_one_notify_file(): reason = NULL\n");
        }
        dprintf("\tcreate_one_notify_file(): symdev = %s\n", symdev);

        result = TRUE;
        /*
         * Handle Race Condition One:
         *
         *   If NOTIFY_DIR exists, make sure it is not a symlink.
         *   if it is, remove it and try to create it.  Check
         *   again to make sure NOTIFY_DIR isn't a symlink.
         *   If it is, remove it and return without creating
         *   a notification file.  The condition can only occur if
         *   someone is trying to break into the system by running
         *   a program that repeatedly creates NOTIFY_DIR as a
         *   symlink.  If NOTIFY_DIR exists and isn't a symlink,
         *   change the working directory to NOTIFY_DIR.
         */
        current_working_dir_fd = pushdir(NOTIFY_DIR);
        if (current_working_dir_fd < 0) {
                (void) makepath(NOTIFY_DIR, 0777);
                current_working_dir_fd = pushdir(NOTIFY_DIR);
                if (current_working_dir_fd < 0) {
                        result = FALSE;
                }
        }
        /*
         * Handle Race Condition Two:
         *
         * Create the notification file in NOTIFY_DIR.
         * Remove any files with the same name that may already be
         * there, using remove(), as it safely removes directories.
         * Then open the file O_CREAT|O_EXCL, which doesn't follow
         * symlinks and requires that the file not exist already,
         * so the new file actually resides in the current working
         * directory.  Create the file with access mode 644, which
         * renders it unusable by anyone trying to break into the
         * system.
         */
        if (result == TRUE) {
                /*
                 * The current working directory is now NOTIFY_DIR.
                 */
                (void) remove(notify_file);
                file_descriptor =
                    open(notify_file, O_CREAT|O_EXCL|O_WRONLY, 0644);
                if (file_descriptor < 0) {
                        dprintf("%s[%d]: can't create %s/%s; %m\n",
                            __FILE__, __LINE__, NOTIFY_DIR, notify_file);
                        result = FALSE;
                } else {
                        filep = fdopen(file_descriptor, "w");
                        if (filep != NULL) {
                                if (reason == NULL) {
                                        (void) fprintf(filep, "%s %s %s",
                                            mount_point,
                                            raw_partitionp,
                                            fstype);
                                        (void) fclose(filep);
                                dprintf("%s[%d]: Just wrote %s %s %s to %s\n",
                                    __FILE__,
                                    __LINE__,
                                    mount_point,
                                    raw_partitionp,
                                    fstype,
                                    notify_file);
                                } else {
                                        (void) fprintf(filep, "%s %s",
                                            reason, raw_partitionp);
                                        (void) fclose(filep);
                                dprintf("%s[%d]: Just wrote %s %s to %s\n",
                                    __FILE__,
                                    __LINE__,
                                    reason,
                                    raw_partitionp,
                                    notify_file);
                                }
                        } else {
                                dprintf("%s[%d]: can't write %s/%s; %m\n",
                                    __FILE__, __LINE__,
                                    NOTIFY_DIR, notify_file);
                                (void) close(file_descriptor);
                                result = FALSE;
                        }
                }
                popdir(current_working_dir_fd);
        }
        dprintf("%s[%d]: leaving create_one_notify_file, result = %s\n",
            __FILE__, __LINE__, result_strings[result]);
        return (result);
}

static boolean_t
notify_clients(action_t action, int do_notify)
{
        /*
         * Notify interested applications of changes in the state
         * of removable media.  Interested applications are those
         * that create a named pipe in NOTIFY_DIR with a name that
         * begins with "notify".  Open the pipe and write a
         * character through it that indicates the type of state
         * change = 'e' for ejections, 'i' for insertions, 'r'
         * for remounts of the file systems on repartitioned media,
         * and 'u' for unmounts of file systems.
         */

        int             current_working_dir_fd;
        DIR             *dirp;
        struct dirent   *dir_entryp;
        size_t          len;
        int             fd;
        char            namebuf[MAXPATHLEN];
        char            notify_character;
        void            (*old_signal_handler)();
        int             result;
        struct stat     sb;

        dprintf("%s[%d]: entering notify_clients()\n", __FILE__, __LINE__);

        result = TRUE;
        /*
         * Use relative pathnames after changing the
         * working directory to the notification directory.
         * Check to make sure that each "notify" file is a
         * named pipe to make sure that it hasn't changed
         * its file type, which could mean that someone is
         * trying to use "notify" files to break into the
         * system.
         */
        if ((current_working_dir_fd = pushdir(NOTIFY_DIR)) < 0) {
                result = FALSE;
        }
        if (result == TRUE) {
                dirp = opendir(".");
                if (dirp == NULL) {
                        dprintf("%s[%d]:opendir failed on '.'; %m\n",
                            __FILE__, __LINE__);
                        popdir(current_working_dir_fd);
                        result = FALSE;
                }
        }
        if (result == TRUE) {
                /*
                 * Read through the directory and write a notify
                 * character to all files whose names start with "notify".
                 */
                result = FALSE;
                old_signal_handler = signal(SIGPIPE, SIG_IGN);
                len = strlen(NOTIFY_NAME);
                while (dir_entryp = readdir(dirp)) {
                        if (strncmp(dir_entryp->d_name, NOTIFY_NAME, len)
                            != 0) {
                                continue;
                        }
                        result = TRUE;
                        if (do_notify != TRUE) {
                                continue;
                        }
                        (void) sprintf(namebuf, "%s/%s",
                            NOTIFY_DIR, dir_entryp->d_name);
                        if ((fd = open(namebuf, O_WRONLY|O_NDELAY)) < 0) {
                                dprintf("%s[%d]: open failed for %s; %m\n",
                                    __FILE__, __LINE__, namebuf);
                                continue;
                        }
                        /*
                         * Check to be sure that the entry is a named pipe.
                         * That closes a small security hole that could
                         * enable unauthorized access to the system root.
                         */
                        if ((fstat(fd, &sb) < 0) || (!S_ISFIFO(sb.st_mode))) {
                                dprintf("%s[%d]: %s isn't a named pipe\n",
                                    __FILE__, __LINE__, namebuf);

                                (void) close(fd);
                                continue;
                        }
                        notify_character = notify_characters[action];
                        if (write(fd, &notify_character, 1) < 0) {
                                dprintf("%s[%d]: write failed for %s; %m\n",
                                    __FILE__, __LINE__, namebuf);
                                (void) close(fd);
                                continue;
                        }
                        (void) close(fd);
                }
                (void) closedir(dirp);
                (void) signal(SIGPIPE, old_signal_handler);
                popdir(current_working_dir_fd);
        }
        dprintf("%s[%d]: leaving notify_clients(), result = %s\n",
            __FILE__, __LINE__, result_strings[result]);
        return (result);
}

static void
popdir(int fd)
{
        /*
         * Change the current working directory to the directory
         * specified by fd and close the fd.  Exit the program
         * on failure.
         */
        if (fchdir(fd) < 0) {
                dprintf("%s[%d]: popdir() failed\n", __FILE__, __LINE__);
                exit(1);
        }
        (void) close(fd);
}

static int
pushdir(const char *dir)
{
        /*
         * Change the current working directory to dir and
         * return a file descriptor for the old working
         * directory.
         *
         * Exception handling:
         *
         * If dir doesn't exist, leave the current working
         * directory the same and return -1.
         *
         * If dir isn't a directory, remove it, leave the
         * current working directory the same, and return -1.
         *
         * If open() fails on the current working directory
         * or the chdir operation fails on dir, leave the
         * current working directory the same and return -1.
         */

        int             current_working_dir_fd;
        struct stat     stat_buf;

        if (lstat(dir, &stat_buf) < 0) {
                dprintf("%s[%d]: push_dir_and_check(): %s does not exist\n",
                    __FILE__, __LINE__, dir);
                return (-1);
        }

        if (!(S_ISDIR(stat_buf.st_mode))) {
                dprintf("%s[%d]: push_dir_and_check(): %s not a directory.\n",
                    __FILE__, __LINE__, dir);
                (void) remove(dir);
                return (-1);
        }
        if ((current_working_dir_fd = open(".", O_RDONLY)) < 0) {
                dprintf("%s[%d]: push_dir_and_check(): can't open %s.\n",
                    __FILE__, __LINE__, dir);
                return (-1);
        }
        if (chdir(dir) < 0) {
                (void) close(current_working_dir_fd);
                dprintf("%s[%d]: push_dir_and_check(): can't chdir() to %s.\n",
                    __FILE__, __LINE__, dir);
                return (-1);
        }
        return (current_working_dir_fd);
}

static boolean_t
remove_notify_files(struct action_arg **aa)
{
        int     ai;
        int     current_working_dir_fd;
        char    notify_file[64];
        int     result;
        char    *symdev;

        dprintf("%s[%d]: entering remove_notify_files()\n", __FILE__, __LINE__);

        ai = 0;
        result = TRUE;
        symdev = aa[ai]->aa_symdev;
        while ((result == TRUE) &&
            (aa[ai] != NULL) &&
            (aa[ai]->aa_path != NULL)) {

                if (not_mountable(aa[ai])) {
                        sprintf(notify_file, "%s-0", symdev);
                } else if (aa[ai]->aa_partname != NULL) {
                        /*
                         * Is aa_partname ever NULL?
                         * When time permits, check.
                         * If it is, the action taken
                         * in the else clause could produce
                         * file name conflicts.
                         */
                        sprintf(notify_file, "%s-%s",
                            symdev, aa[0]->aa_partname);
                } else {
                        sprintf(notify_file, "%s-0", symdev);
                }

                current_working_dir_fd = pushdir(NOTIFY_DIR);
                if (current_working_dir_fd < 0) {
                        result = FALSE;
                }
                if ((result == TRUE) && (remove(notify_file) < 0)) {
                        dprintf("%s[%d]: remove %s/%s; %m\n",
                            __FILE__, __LINE__, NOTIFY_DIR, notify_file);
                        result = FALSE;
                }
                if (current_working_dir_fd != -1) {
                        popdir(current_working_dir_fd);
                }
                ai++;
        }
        dprintf("%s[%d]: leaving remove_notify_files(), result = %s\n",
            __FILE__, __LINE__, result_strings[result]);

        return (result);
}