mount.c

/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2007  Miklos Szeredi <miklos@szeredi.hu>

  Architecture specific file system mounting (Linux).

  This program can be distributed under the terms of the GNU LGPLv2.
  See the file COPYING.LIB.
*/

#include "config.h"
#include "fuse_i.h"
#include "fuse_misc.h"
#include "fuse_opt.h"
#include "mount_util.h"

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <stddef.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <poll.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/wait.h>
#include <sys/mount.h>

#ifdef __NetBSD__
#include <perfuse.h>

#define MS_RDONLY       MNT_RDONLY
#define MS_NOSUID       MNT_NOSUID
#define MS_NODEV        MNT_NODEV
#define MS_NOEXEC       MNT_NOEXEC
#define MS_SYNCHRONOUS  MNT_SYNCHRONOUS
#define MS_NOATIME      MNT_NOATIME

#define umount2(mnt, flags) unmount(mnt, (flags == 2) ? MNT_FORCE : 0)
#endif

#define FUSERMOUNT_PROG         "fusermount3"
#define FUSE_COMMFD_ENV         "_FUSE_COMMFD"

#ifndef HAVE_FORK
#define fork() vfork()
#endif

#ifndef MS_DIRSYNC
#define MS_DIRSYNC 128
#endif

enum {
        KEY_KERN_FLAG,
        KEY_KERN_OPT,
        KEY_FUSERMOUNT_OPT,
        KEY_SUBTYPE_OPT,
        KEY_MTAB_OPT,
        KEY_ALLOW_OTHER,
        KEY_RO,
};

struct mount_opts {
        int allow_other;
        int flags;
        int auto_unmount;
        int blkdev;
        char *fsname;
        char *subtype;
        char *subtype_opt;
        char *mtab_opts;
        char *fusermount_opts;
        char *kernel_opts;
        unsigned max_read;
};

#define FUSE_MOUNT_OPT(t, p) { t, offsetof(struct mount_opts, p), 1 }

static const struct fuse_opt fuse_mount_opts[] = {
        FUSE_MOUNT_OPT("allow_other",           allow_other),
        FUSE_MOUNT_OPT("blkdev",                blkdev),
        FUSE_MOUNT_OPT("auto_unmount",          auto_unmount),
        FUSE_MOUNT_OPT("fsname=%s",             fsname),
        FUSE_MOUNT_OPT("max_read=%u",           max_read),
        FUSE_MOUNT_OPT("subtype=%s",            subtype),
        FUSE_OPT_KEY("allow_other",             KEY_KERN_OPT),
        FUSE_OPT_KEY("auto_unmount",            KEY_FUSERMOUNT_OPT),
        FUSE_OPT_KEY("blkdev",                  KEY_FUSERMOUNT_OPT),
        FUSE_OPT_KEY("fsname=",                 KEY_FUSERMOUNT_OPT),
        FUSE_OPT_KEY("subtype=",                KEY_SUBTYPE_OPT),
        FUSE_OPT_KEY("blksize=",                KEY_KERN_OPT),
        FUSE_OPT_KEY("default_permissions",     KEY_KERN_OPT),
        FUSE_OPT_KEY("context=",                KEY_KERN_OPT),
        FUSE_OPT_KEY("fscontext=",              KEY_KERN_OPT),
        FUSE_OPT_KEY("defcontext=",             KEY_KERN_OPT),
        FUSE_OPT_KEY("rootcontext=",            KEY_KERN_OPT),
        FUSE_OPT_KEY("max_read=",               KEY_KERN_OPT),
        FUSE_OPT_KEY("user=",                   KEY_MTAB_OPT),
        FUSE_OPT_KEY("-r",                      KEY_RO),
        FUSE_OPT_KEY("ro",                      KEY_KERN_FLAG),
        FUSE_OPT_KEY("rw",                      KEY_KERN_FLAG),
        FUSE_OPT_KEY("suid",                    KEY_KERN_FLAG),
        FUSE_OPT_KEY("nosuid",                  KEY_KERN_FLAG),
        FUSE_OPT_KEY("dev",                     KEY_KERN_FLAG),
        FUSE_OPT_KEY("nodev",                   KEY_KERN_FLAG),
        FUSE_OPT_KEY("exec",                    KEY_KERN_FLAG),
        FUSE_OPT_KEY("noexec",                  KEY_KERN_FLAG),
        FUSE_OPT_KEY("async",                   KEY_KERN_FLAG),
        FUSE_OPT_KEY("sync",                    KEY_KERN_FLAG),
        FUSE_OPT_KEY("dirsync",                 KEY_KERN_FLAG),
        FUSE_OPT_KEY("atime",                   KEY_KERN_FLAG),
        FUSE_OPT_KEY("noatime",                 KEY_KERN_FLAG),
        FUSE_OPT_END
};

static void exec_fusermount(const char *argv[])
{
        execv(FUSERMOUNT_DIR "/" FUSERMOUNT_PROG, (char **) argv);
        execvp(FUSERMOUNT_PROG, (char **) argv);
}

void fuse_mount_version(void)
{
        int pid = fork();
        if (!pid) {
                const char *argv[] = { FUSERMOUNT_PROG, "--version", NULL };
                exec_fusermount(argv);
                _exit(1);
        } else if (pid != -1)
                waitpid(pid, NULL, 0);
}

struct mount_flags {
        const char *opt;
        unsigned long flag;
        int on;
};

static const struct mount_flags mount_flags[] = {
        {"rw",      MS_RDONLY,      0},
        {"ro",      MS_RDONLY,      1},
        {"suid",    MS_NOSUID,      0},
        {"nosuid",  MS_NOSUID,      1},
        {"dev",     MS_NODEV,       0},
        {"nodev",   MS_NODEV,       1},
        {"exec",    MS_NOEXEC,      0},
        {"noexec",  MS_NOEXEC,      1},
        {"async",   MS_SYNCHRONOUS, 0},
        {"sync",    MS_SYNCHRONOUS, 1},
        {"atime",   MS_NOATIME,     0},
        {"noatime", MS_NOATIME,     1},
#ifndef __NetBSD__
        {"dirsync", MS_DIRSYNC,     1},
#endif
        {NULL,      0,              0}
};

unsigned get_max_read(struct mount_opts *o)
{
        return o->max_read;
}

static void set_mount_flag(const char *s, int *flags)
{
        int i;

        for (i = 0; mount_flags[i].opt != NULL; i++) {
                const char *opt = mount_flags[i].opt;
                if (strcmp(opt, s) == 0) {
                        if (mount_flags[i].on)
                                *flags |= mount_flags[i].flag;
                        else
                                *flags &= ~mount_flags[i].flag;
                        return;
                }
        }
        fuse_log(FUSE_LOG_ERR, "fuse: internal error, can't find mount flag\n");
        abort();
}

static int fuse_mount_opt_proc(void *data, const char *arg, int key,
                               struct fuse_args *outargs)
{
        (void) outargs;
        struct mount_opts *mo = data;

        switch (key) {
        case KEY_RO:
                arg = "ro";
                /* fall through */
        case KEY_KERN_FLAG:
                set_mount_flag(arg, &mo->flags);
                return 0;

        case KEY_KERN_OPT:
                return fuse_opt_add_opt(&mo->kernel_opts, arg);

        case KEY_FUSERMOUNT_OPT:
                return fuse_opt_add_opt_escaped(&mo->fusermount_opts, arg);

        case KEY_SUBTYPE_OPT:
                return fuse_opt_add_opt(&mo->subtype_opt, arg);

        case KEY_MTAB_OPT:
                return fuse_opt_add_opt(&mo->mtab_opts, arg);
        }

        /* Pass through unknown options */
        return 1;
}

/* return value:
 * >= 0  => fd
 * -1    => error
 */
static int receive_fd(int fd)
{
        struct msghdr msg;
        struct iovec iov;
        char buf[1];
        int rv;
        size_t ccmsg[CMSG_SPACE(sizeof(int)) / sizeof(size_t)];
        struct cmsghdr *cmsg;

        iov.iov_base = buf;
        iov.iov_len = 1;

        memset(&msg, 0, sizeof(msg));
        msg.msg_name = 0;
        msg.msg_namelen = 0;
        msg.msg_iov = &iov;
        msg.msg_iovlen = 1;
        /* old BSD implementations should use msg_accrights instead of
         * msg_control; the interface is different. */
        msg.msg_control = ccmsg;
        msg.msg_controllen = sizeof(ccmsg);

        while(((rv = recvmsg(fd, &msg, 0)) == -1) && errno == EINTR);
        if (rv == -1) {
                perror("recvmsg");
                return -1;
        }
        if(!rv) {
                /* EOF */
                return -1;
        }

        cmsg = CMSG_FIRSTHDR(&msg);
        if (cmsg->cmsg_type != SCM_RIGHTS) {
                fuse_log(FUSE_LOG_ERR, "got control message of unknown type %d\n",
                        cmsg->cmsg_type);
                return -1;
        }
        return *(int*)CMSG_DATA(cmsg);
}

void fuse_kern_unmount(const char *mountpoint, int fd)
{
        int res;
        int pid;

        if (fd != -1) {
                struct pollfd pfd;

                pfd.fd = fd;
                pfd.events = 0;
                res = poll(&pfd, 1, 0);

                /* Need to close file descriptor, otherwise synchronous umount
                   would recurse into filesystem, and deadlock.

                   Caller expects fuse_kern_unmount to close the fd, so close it
                   anyway. */
                close(fd);

                /* If file poll returns POLLERR on the device file descriptor,
                   then the filesystem is already unmounted or the connection
                   was severed via /sys/fs/fuse/connections/NNN/abort */
                if (res == 1 && (pfd.revents & POLLERR))
                        return;
        }

        if (geteuid() == 0) {
                fuse_mnt_umount("fuse", mountpoint, mountpoint,  1);
                return;
        }

        res = umount2(mountpoint, 2);
        if (res == 0)
                return;

        pid = fork();
        if(pid == -1)
                return;

        if(pid == 0) {
                const char *argv[] = { FUSERMOUNT_PROG, "-u", "-q", "-z",
                                       "--", mountpoint, NULL };

                exec_fusermount(argv);
                _exit(1);
        }
        waitpid(pid, NULL, 0);
}

static int fuse_mount_fusermount(const char *mountpoint, struct mount_opts *mo,
                const char *opts, int quiet)
{
        int fds[2], pid;
        int res;
        int rv;

        if (!mountpoint) {
                fuse_log(FUSE_LOG_ERR, "fuse: missing mountpoint parameter\n");
                return -1;
        }

        res = socketpair(PF_UNIX, SOCK_STREAM, 0, fds);
        if(res == -1) {
                perror("fuse: socketpair() failed");
                return -1;
        }

        pid = fork();
        if(pid == -1) {
                perror("fuse: fork() failed");
                close(fds[0]);
                close(fds[1]);
                return -1;
        }

        if(pid == 0) {
                char env[10];
                const char *argv[32];
                int a = 0;

                if (quiet) {
                        int fd = open("/dev/null", O_RDONLY);
                        if (fd != -1) {
                                dup2(fd, 1);
                                dup2(fd, 2);
                        }
                }

                argv[a++] = FUSERMOUNT_PROG;
                if (opts) {
                        argv[a++] = "-o";
                        argv[a++] = opts;
                }
                argv[a++] = "--";
                argv[a++] = mountpoint;
                argv[a++] = NULL;

                close(fds[1]);
                fcntl(fds[0], F_SETFD, 0);
                snprintf(env, sizeof(env), "%i", fds[0]);
                setenv(FUSE_COMMFD_ENV, env, 1);
                exec_fusermount(argv);
                perror("fuse: failed to exec fusermount3");
                _exit(1);
        }

        close(fds[0]);
        rv = receive_fd(fds[1]);

        if (!mo->auto_unmount) {
                /* with auto_unmount option fusermount3 will not exit until
                   this socket is closed */
                close(fds[1]);
                waitpid(pid, NULL, 0); /* bury zombie */
        }

        if (rv >= 0)
                fcntl(rv, F_SETFD, FD_CLOEXEC);

        return rv;
}

#ifndef O_CLOEXEC
#define O_CLOEXEC 0
#endif

static int fuse_mount_sys(const char *mnt, struct mount_opts *mo,
                          const char *mnt_opts)
{
        char tmp[128];
        const char *devname = "/dev/fuse";
        char *source = NULL;
        char *type = NULL;
        struct stat stbuf;
        int fd;
        int res;

        if (!mnt) {
                fuse_log(FUSE_LOG_ERR, "fuse: missing mountpoint parameter\n");
                return -1;
        }

        res = stat(mnt, &stbuf);
        if (res == -1) {
                fuse_log(FUSE_LOG_ERR, "fuse: failed to access mountpoint %s: %s\n",
                        mnt, strerror(errno));
                return -1;
        }

        if (mo->auto_unmount) {
                /* Tell the caller to fallback to fusermount3 because
                   auto-unmount does not work otherwise. */
                return -2;
        }

        fd = open(devname, O_RDWR | O_CLOEXEC);
        if (fd == -1) {
                if (errno == ENODEV || errno == ENOENT)
                        fuse_log(FUSE_LOG_ERR, "fuse: device not found, try 'modprobe fuse' first\n");
                else
                        fuse_log(FUSE_LOG_ERR, "fuse: failed to open %s: %s\n",
                                devname, strerror(errno));
                return -1;
        }
        if (!O_CLOEXEC)
                fcntl(fd, F_SETFD, FD_CLOEXEC);

        snprintf(tmp, sizeof(tmp),  "fd=%i,rootmode=%o,user_id=%u,group_id=%u",
                 fd, stbuf.st_mode & S_IFMT, getuid(), getgid());

        res = fuse_opt_add_opt(&mo->kernel_opts, tmp);
        if (res == -1)
                goto out_close;

        source = malloc((mo->fsname ? strlen(mo->fsname) : 0) +
                        (mo->subtype ? strlen(mo->subtype) : 0) +
                        strlen(devname) + 32);

        type = malloc((mo->subtype ? strlen(mo->subtype) : 0) + 32);
        if (!type || !source) {
                fuse_log(FUSE_LOG_ERR, "fuse: failed to allocate memory\n");
                goto out_close;
        }

        strcpy(type, mo->blkdev ? "fuseblk" : "fuse");
        if (mo->subtype) {
                strcat(type, ".");
                strcat(type, mo->subtype);
        }
        strcpy(source,
               mo->fsname ? mo->fsname : (mo->subtype ? mo->subtype : devname));

        res = mount(source, mnt, type, mo->flags, mo->kernel_opts);
        if (res == -1 && errno == ENODEV && mo->subtype) {
                /* Probably missing subtype support */
                strcpy(type, mo->blkdev ? "fuseblk" : "fuse");
                if (mo->fsname) {
                        if (!mo->blkdev)
                                sprintf(source, "%s#%s", mo->subtype,
                                        mo->fsname);
                } else {
                        strcpy(source, type);
                }
                res = mount(source, mnt, type, mo->flags, mo->kernel_opts);
        }
        if (res == -1) {
                /*
                 * Maybe kernel doesn't support unprivileged mounts, in this
                 * case try falling back to fusermount3
                 */
                if (errno == EPERM) {
                        res = -2;
                } else {
                        int errno_save = errno;
                        if (mo->blkdev && errno == ENODEV &&
                            !fuse_mnt_check_fuseblk())
                                fuse_log(FUSE_LOG_ERR,
                                        "fuse: 'fuseblk' support missing\n");
                        else
                                fuse_log(FUSE_LOG_ERR, "fuse: mount failed: %s\n",
                                        strerror(errno_save));
                }

                goto out_close;
        }

#ifndef IGNORE_MTAB
        if (geteuid() == 0) {
                char *newmnt = fuse_mnt_resolve_path("fuse", mnt);
                res = -1;
                if (!newmnt)
                        goto out_umount;

                res = fuse_mnt_add_mount("fuse", source, newmnt, type,
                                         mnt_opts);
                free(newmnt);
                if (res == -1)
                        goto out_umount;
        }
#endif /* IGNORE_MTAB */
        free(type);
        free(source);

        return fd;

out_umount:
        umount2(mnt, 2); /* lazy umount */
out_close:
        free(type);
        free(source);
        close(fd);
        return res;
}

static int get_mnt_flag_opts(char **mnt_optsp, int flags)
{
        int i;

        if (!(flags & MS_RDONLY) && fuse_opt_add_opt(mnt_optsp, "rw") == -1)
                return -1;

        for (i = 0; mount_flags[i].opt != NULL; i++) {
                if (mount_flags[i].on && (flags & mount_flags[i].flag) &&
                    fuse_opt_add_opt(mnt_optsp, mount_flags[i].opt) == -1)
                        return -1;
        }
        return 0;
}

struct mount_opts *parse_mount_opts(struct fuse_args *args)
{
        struct mount_opts *mo;

        mo = (struct mount_opts*) malloc(sizeof(struct mount_opts));
        if (mo == NULL)
                return NULL;

        memset(mo, 0, sizeof(struct mount_opts));
        mo->flags = MS_NOSUID | MS_NODEV;

        if (args &&
            fuse_opt_parse(args, mo, fuse_mount_opts, fuse_mount_opt_proc) == -1)
                goto err_out;

        return mo;

err_out:
        destroy_mount_opts(mo);
        return NULL;
}

void destroy_mount_opts(struct mount_opts *mo)
{
        free(mo->fsname);
        free(mo->subtype);
        free(mo->fusermount_opts);
        free(mo->subtype_opt);
        free(mo->kernel_opts);
        free(mo->mtab_opts);
        free(mo);
}


int fuse_kern_mount(const char *mountpoint, struct mount_opts *mo)
{
        int res = -1;
        char *mnt_opts = NULL;

        res = -1;
        if (get_mnt_flag_opts(&mnt_opts, mo->flags) == -1)
                goto out;
        if (mo->kernel_opts && fuse_opt_add_opt(&mnt_opts, mo->kernel_opts) == -1)
                goto out;
        if (mo->mtab_opts &&  fuse_opt_add_opt(&mnt_opts, mo->mtab_opts) == -1)
                goto out;

        res = fuse_mount_sys(mountpoint, mo, mnt_opts);
        if (res == -2) {
                if (mo->fusermount_opts &&
                    fuse_opt_add_opt(&mnt_opts, mo->fusermount_opts) == -1)
                        goto out;

                if (mo->subtype) {
                        char *tmp_opts = NULL;

                        res = -1;
                        if (fuse_opt_add_opt(&tmp_opts, mnt_opts) == -1 ||
                            fuse_opt_add_opt(&tmp_opts, mo->subtype_opt) == -1) {
                                free(tmp_opts);
                                goto out;
                        }

                        res = fuse_mount_fusermount(mountpoint, mo, tmp_opts, 1);
                        free(tmp_opts);
                        if (res == -1)
                                res = fuse_mount_fusermount(mountpoint, mo,
                                                            mnt_opts, 0);
                } else {
                        res = fuse_mount_fusermount(mountpoint, mo, mnt_opts, 0);
                }
        }
out:
        free(mnt_opts);
        return res;
}