be_access.c

/*
 * Copyright (c) 2017 Kyle J. Kneitinger <[email protected]>
 * Copyright (c) 2018 Kyle Evans <[email protected]>
 * Copyright (c) 2019 Wes Maag <[email protected]>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <sys/cdefs.h>
#include <sys/mntent.h>

#include "be.h"
#include "be_impl.h"

#define	LIBBE_MOUNT_PREFIX	"be_mount."

struct be_mountcheck_info {
	const char *path;
	char *name;
};

struct be_mount_info {
	libbe_handle_t *lbh;
	const char *be;
	const char *mountpoint;
	int mntflags;
	int deepmount;
	int depth;
};

static int
be_mountcheck_cb(zfs_handle_t *zfs_hdl, void *data)
{
	struct be_mountcheck_info *info;
	char *mountpoint;

	if (data == NULL)
		return (1);
	info = (struct be_mountcheck_info *)data;
	if (!zfs_is_mounted(zfs_hdl, &mountpoint))
		return (0);
	if (strcmp(mountpoint, info->path) == 0) {
		info->name = strdup(zfs_get_name(zfs_hdl));
		free(mountpoint);
		return (1);
	}
	free(mountpoint);
	return (0);
}

/*
 * Called from be_mount, uses the given zfs_handle and attempts to
 * mount it at the passed mountpoint. If the deepmount flag is set, continue
 * calling the function for each child dataset.
 */
static int
be_mount_iter(zfs_handle_t *zfs_hdl, void *data)
{
	int err;
	char *mountpoint;
	char tmp[BE_MAXPATHLEN], zfs_mnt[BE_MAXPATHLEN];
	struct be_mount_info *info;

	info = (struct be_mount_info *)data;

	if (zfs_is_mounted(zfs_hdl, &mountpoint)) {
		free(mountpoint);
		return (0);
	}

	/*
	 * canmount and mountpoint are both ignored for the BE dataset, because
	 * the rest of the system (kernel and loader) will effectively do the
	 * same.
	 */
	if (info->depth == 0) {
		snprintf(tmp, BE_MAXPATHLEN, "%s", info->mountpoint);
	} else {
		if (zfs_prop_get_int(zfs_hdl, ZFS_PROP_CANMOUNT) ==
		    ZFS_CANMOUNT_OFF)
			return (0);

		if (zfs_prop_get(zfs_hdl, ZFS_PROP_MOUNTPOINT, zfs_mnt,
		    BE_MAXPATHLEN, NULL, NULL, 0, 1))
			return (1);

		/*
		 * We've encountered mountpoint=none at some intermediate
		 * dataset (e.g. zroot/var) that will have children that may
		 * need to be mounted.  Skip mounting it, but iterate through
		 * the children.
		 */
		if (strcmp("none", zfs_mnt) == 0)
			goto skipmount;

		mountpoint = be_mountpoint_augmented(info->lbh, zfs_mnt);
		snprintf(tmp, BE_MAXPATHLEN, "%s%s", info->mountpoint,
		    mountpoint);
	}

	if ((err = zfs_mount_at(zfs_hdl, NULL, info->mntflags, tmp)) != 0) {
		switch (errno) {
		case ENAMETOOLONG:
			return (set_error(info->lbh, BE_ERR_PATHLEN));
		case ELOOP:
		case ENOENT:
		case ENOTDIR:
			return (set_error(info->lbh, BE_ERR_BADPATH));
		case EPERM:
			return (set_error(info->lbh, BE_ERR_PERMS));
		case EBUSY:
			return (set_error(info->lbh, BE_ERR_PATHBUSY));
		default:
			return (set_error(info->lbh, BE_ERR_UNKNOWN));
		}
	}

	if (!info->deepmount)
		return (0);

skipmount:
	++info->depth;
	err = zfs_iter_filesystems(zfs_hdl, be_mount_iter, info);
	--info->depth;
	return (err);
}


static int
be_umount_iter(zfs_handle_t *zfs_hdl, void *data)
{

	int err;
	char *mountpoint;
	struct be_mount_info *info;

	info = (struct be_mount_info *)data;

	++info->depth;
	if((err = zfs_iter_filesystems(zfs_hdl, be_umount_iter, info)) != 0) {
		return (err);
	}
	--info->depth;

	if (!zfs_is_mounted(zfs_hdl, &mountpoint)) {
		return (0);
	}

	if (info->depth == 0 && info->mountpoint == NULL)
		info->mountpoint = mountpoint;
	else
		free(mountpoint);

	if (zfs_unmount(zfs_hdl, NULL, info->mntflags) != 0) {
		switch (errno) {
		case ENAMETOOLONG:
			return (set_error(info->lbh, BE_ERR_PATHLEN));
		case ELOOP:
		case ENOENT:
		case ENOTDIR:
			return (set_error(info->lbh, BE_ERR_BADPATH));
		case EPERM:
			return (set_error(info->lbh, BE_ERR_PERMS));
		case EBUSY:
			return (set_error(info->lbh, BE_ERR_PATHBUSY));
		default:
			return (set_error(info->lbh, BE_ERR_UNKNOWN));
		}
	}
	return (0);
}

/*
 * usage
 */
int
be_mounted_at(libbe_handle_t *lbh, const char *path, nvlist_t *details)
{
	char be[BE_MAXPATHLEN];
	zfs_handle_t *root_hdl;
	struct be_mountcheck_info info;
	prop_data_t propinfo;

	bzero(&be, BE_MAXPATHLEN);
	if ((root_hdl = zfs_open(lbh->lzh, lbh->root,
	    ZFS_TYPE_FILESYSTEM)) == NULL)
		return (BE_ERR_ZFSOPEN);

	info.path = path;
	info.name = NULL;
	zfs_iter_filesystems(root_hdl, be_mountcheck_cb, &info);
	zfs_close(root_hdl);

	if (info.name != NULL) {
		if (details != NULL) {
			if ((root_hdl = zfs_open(lbh->lzh, info.name,
			    ZFS_TYPE_FILESYSTEM)) == NULL) {
				free(info.name);
				return (BE_ERR_ZFSOPEN);
			}

			propinfo.lbh = lbh;
			propinfo.list = details;
			propinfo.single_object = false;
			propinfo.bootonce = NULL;
			prop_list_builder_cb(root_hdl, &propinfo);
			zfs_close(root_hdl);
		}
		free(info.name);
		return (0);
	}
	return (1);
}

/*
 * usage
 */
int
be_mount(libbe_handle_t *lbh, const char *bootenv, const char *mountpoint,
    int flags, char *result_loc)
{
	char be[BE_MAXPATHLEN];
	char mnt_temp[BE_MAXPATHLEN];
	int mntflags, mntdeep;
	int err;
	struct be_mount_info info;
	zfs_handle_t *zhdl;

	if ((err = be_root_concat(lbh, bootenv, be)) != 0)
		return (set_error(lbh, err));

	if ((err = be_exists(lbh, bootenv)) != 0)
		return (set_error(lbh, err));

	if (is_mounted(lbh->lzh, be, NULL))
		return (set_error(lbh, BE_ERR_MOUNTED));

	mntdeep = (flags & BE_MNT_DEEP) ? 1 : 0;
	mntflags = (flags & BE_MNT_FORCE) ? MNT_FORCE : 0;

	/* Create mountpoint if it is not specified */
	if (mountpoint == NULL) {
		const char *tmpdir;

		tmpdir = getenv("TMPDIR");
		if (tmpdir == NULL)
			tmpdir = _PATH_TMP;

		if (snprintf(mnt_temp, sizeof(mnt_temp), "%s%s%sXXXX", tmpdir,
		    tmpdir[strlen(tmpdir) - 1] == '/' ? "" : "/",
		     LIBBE_MOUNT_PREFIX) >= (int)sizeof(mnt_temp))
			return (set_error(lbh, BE_ERR_PATHLEN));

		if (mkdtemp(mnt_temp) == NULL)
			return (set_error(lbh, BE_ERR_IO));
	}

	if ((zhdl = zfs_open(lbh->lzh, be, ZFS_TYPE_FILESYSTEM)) == NULL)
		return (set_error(lbh, BE_ERR_ZFSOPEN));

	info.lbh = lbh;
	info.be = be;
	info.mountpoint = (mountpoint == NULL) ? mnt_temp : mountpoint;
	info.mntflags = mntflags;
	info.deepmount = mntdeep;
	info.depth = 0;

	if((err = be_mount_iter(zhdl, &info) != 0)) {
		zfs_close(zhdl);
		return (err);
	}
	zfs_close(zhdl);

	if (result_loc != NULL)
		strlcpy(result_loc, mountpoint == NULL ? mnt_temp : mountpoint,
		    BE_MAXPATHLEN);

	return (BE_ERR_SUCCESS);
}

/*
 * usage
 */
int
be_unmount(libbe_handle_t *lbh, const char *bootenv, int flags)
{
	int err;
	char be[BE_MAXPATHLEN];
	zfs_handle_t *root_hdl;
	struct be_mount_info info;

	if ((err = be_root_concat(lbh, bootenv, be)) != 0)
		return (set_error(lbh, err));

	if ((root_hdl = zfs_open(lbh->lzh, be, ZFS_TYPE_FILESYSTEM)) == NULL)
		return (set_error(lbh, BE_ERR_ZFSOPEN));

	info.lbh = lbh;
	info.be = be;
	info.mountpoint = NULL;
	info.mntflags = (flags & BE_MNT_FORCE) ? MS_FORCE : 0;
	info.depth = 0;

	if ((err = be_umount_iter(root_hdl, &info)) != 0) {
		free(__DECONST(char *, info.mountpoint));
		zfs_close(root_hdl);
		return (err);
	}

	/*
	 * We'll attempt to remove the directory if we created it on a
	 * best-effort basis.  rmdir(2) failure will not be reported.
	 */
	if (info.mountpoint != NULL) {
		const char *mdir;

		mdir = strrchr(info.mountpoint, '/');
		if (mdir == NULL)
			mdir = info.mountpoint;
		else
			mdir++;

		if (strncmp(mdir, LIBBE_MOUNT_PREFIX,
		    sizeof(LIBBE_MOUNT_PREFIX) - 1) == 0) {
			(void)rmdir(info.mountpoint);
		}
	}

	free(__DECONST(char *, info.mountpoint));

	zfs_close(root_hdl);
	return (BE_ERR_SUCCESS);
}

/*
 * This function will blow away the input buffer as needed if we're discovered
 * to be looking at a root-mount.  If the mountpoint is naturally beyond the
 * root, however, the buffer may be left intact and a pointer to the section
 * past altroot will be returned instead for the caller's perusal.
 */
char *
be_mountpoint_augmented(libbe_handle_t *lbh, char *mountpoint)
{

	if (lbh->altroot_len == 0)
		return (mountpoint);
	if (mountpoint == NULL || *mountpoint == '\0')
		return (mountpoint);

	if (mountpoint[lbh->altroot_len] == '\0') {
		*(mountpoint + 1) = '\0';
		return (mountpoint);
	} else
		return (mountpoint + lbh->altroot_len);
}