Fix DR_OVERRIDDEN use-after-free race in dbuf_sync_leaf

[zfs.git] / module / zcommon / zfs_namecheck.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 https://opensource.org/licenses/CDDL-1.0.
 * 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.
 */
/*
 * Copyright (c) 2013, 2016 by Delphix. All rights reserved.
 */

/*
 * Common name validation routines for ZFS.  These routines are shared by the
 * userland code as well as the ioctl() layer to ensure that we don't
 * inadvertently expose a hole through direct ioctl()s that never gets tested.
 * In userland, however, we want significantly more information about _why_ the
 * name is invalid.  In the kernel, we only care whether it's valid or not.
 * Each routine therefore takes a 'namecheck_err_t' which describes exactly why
 * the name failed to validate.
 */

#if !defined(_KERNEL)
#include <string.h>
#endif

#include <sys/dsl_dir.h>
#include <sys/param.h>
#include <sys/nvpair.h>
#include "zfs_namecheck.h"
#include "zfs_deleg.h"

/*
 * Deeply nested datasets can overflow the stack, so we put a limit
 * in the amount of nesting a path can have. zfs_max_dataset_nesting
 * can be tuned temporarily to fix existing datasets that exceed our
 * predefined limit.
 */
int zfs_max_dataset_nesting = 50;

static int
valid_char(char c)
{
        return ((c >= 'a' && c <= 'z') ||
            (c >= 'A' && c <= 'Z') ||
            (c >= '0' && c <= '9') ||
            c == '-' || c == '_' || c == '.' || c == ':' || c == ' ');
}

/*
 * Looks at a path and returns its level of nesting (depth).
 */
int
get_dataset_depth(const char *path)
{
        const char *loc = path;
        int nesting = 0;

        /*
         * Keep track of nesting until you hit the end of the
         * path or found the snapshot/bookmark separator.
         */
        for (int i = 0; loc[i] != '\0' &&
            loc[i] != '@' &&
            loc[i] != '#'; i++) {
                if (loc[i] == '/')
                        nesting++;
        }

        return (nesting);
}

/*
 * Snapshot names must be made up of alphanumeric characters plus the following
 * characters:
 *
 *      [-_.: ]
 *
 * Returns 0 on success, -1 on error.
 */
int
zfs_component_namecheck(const char *path, namecheck_err_t *why, char *what)
{
        const char *loc;

        if (strlen(path) >= ZFS_MAX_DATASET_NAME_LEN) {
                if (why)
                        *why = NAME_ERR_TOOLONG;
                return (-1);
        }

        if (path[0] == '\0') {
                if (why)
                        *why = NAME_ERR_EMPTY_COMPONENT;
                return (-1);
        }

        for (loc = path; *loc; loc++) {
                if (!valid_char(*loc)) {
                        if (why) {
                                *why = NAME_ERR_INVALCHAR;
                                *what = *loc;
                        }
                        return (-1);
                }
        }
        return (0);
}


/*
 * Permissions set name must start with the letter '@' followed by the
 * same character restrictions as snapshot names, except that the name
 * cannot exceed 64 characters.
 *
 * Returns 0 on success, -1 on error.
 */
int
permset_namecheck(const char *path, namecheck_err_t *why, char *what)
{
        if (strlen(path) >= ZFS_PERMSET_MAXLEN) {
                if (why)
                        *why = NAME_ERR_TOOLONG;
                return (-1);
        }

        if (path[0] != '@') {
                if (why) {
                        *why = NAME_ERR_NO_AT;
                        *what = path[0];
                }
                return (-1);
        }

        return (zfs_component_namecheck(&path[1], why, what));
}

/*
 * Dataset paths should not be deeper than zfs_max_dataset_nesting
 * in terms of nesting.
 *
 * Returns 0 on success, -1 on error.
 */
int
dataset_nestcheck(const char *path)
{
        return ((get_dataset_depth(path) < zfs_max_dataset_nesting) ? 0 : -1);
}

/*
 * Entity names must be of the following form:
 *
 *      [component/]*[component][(@|#)component]?
 *
 * Where each component is made up of alphanumeric characters plus the following
 * characters:
 *
 *      [-_.: %]
 *
 * We allow '%' here as we use that character internally to create unique
 * names for temporary clones (for online recv).
 *
 * Returns 0 on success, -1 on error.
 */
int
entity_namecheck(const char *path, namecheck_err_t *why, char *what)
{
        const char *end;

        EQUIV(why == NULL, what == NULL);

        /*
         * Make sure the name is not too long.
         */
        if (strlen(path) >= ZFS_MAX_DATASET_NAME_LEN) {
                if (why)
                        *why = NAME_ERR_TOOLONG;
                return (-1);
        }

        /* Explicitly check for a leading slash.  */
        if (path[0] == '/') {
                if (why)
                        *why = NAME_ERR_LEADING_SLASH;
                return (-1);
        }

        if (path[0] == '\0') {
                if (why)
                        *why = NAME_ERR_EMPTY_COMPONENT;
                return (-1);
        }

        const char *start = path;
        boolean_t found_delim = B_FALSE;
        for (;;) {
                /* Find the end of this component */
                end = start;
                while (*end != '/' && *end != '@' && *end != '#' &&
                    *end != '\0')
                        end++;

                if (*end == '\0' && end[-1] == '/') {
                        /* trailing slashes are not allowed */
                        if (why)
                                *why = NAME_ERR_TRAILING_SLASH;
                        return (-1);
                }

                /* Validate the contents of this component */
                for (const char *loc = start; loc != end; loc++) {
                        if (!valid_char(*loc) && *loc != '%') {
                                if (why) {
                                        *why = NAME_ERR_INVALCHAR;
                                        *what = *loc;
                                }
                                return (-1);
                        }
                }

                if (*end == '\0' || *end == '/') {
                        int component_length = end - start;
                        /* Validate the contents of this component is not '.' */
                        if (component_length == 1) {
                                if (start[0] == '.') {
                                        if (why)
                                                *why = NAME_ERR_SELF_REF;
                                        return (-1);
                                }
                        }

                        /* Validate the content of this component is not '..' */
                        if (component_length == 2) {
                                if (start[0] == '.' && start[1] == '.') {
                                        if (why)
                                                *why = NAME_ERR_PARENT_REF;
                                        return (-1);
                                }
                        }
                }

                /* Snapshot or bookmark delimiter found */
                if (*end == '@' || *end == '#') {
                        /* Multiple delimiters are not allowed */
                        if (found_delim != 0) {
                                if (why)
                                        *why = NAME_ERR_MULTIPLE_DELIMITERS;
                                return (-1);
                        }

                        found_delim = B_TRUE;
                }

                /* Zero-length components are not allowed */
                if (start == end) {
                        if (why)
                                *why = NAME_ERR_EMPTY_COMPONENT;
                        return (-1);
                }

                /* If we've reached the end of the string, we're OK */
                if (*end == '\0')
                        return (0);

                /*
                 * If there is a '/' in a snapshot or bookmark name
                 * then report an error
                 */
                if (*end == '/' && found_delim != 0) {
                        if (why)
                                *why = NAME_ERR_TRAILING_SLASH;
                        return (-1);
                }

                /* Update to the next component */
                start = end + 1;
        }
}

/*
 * Dataset is any entity, except bookmark
 */
int
dataset_namecheck(const char *path, namecheck_err_t *why, char *what)
{
        int ret = entity_namecheck(path, why, what);

        if (ret == 0 && strchr(path, '#') != NULL) {
                if (why != NULL) {
                        *why = NAME_ERR_INVALCHAR;
                        *what = '#';
                }
                return (-1);
        }

        return (ret);
}

/*
 * Assert path is a valid bookmark name
 */
int
bookmark_namecheck(const char *path, namecheck_err_t *why, char *what)
{
        int ret = entity_namecheck(path, why, what);

        if (ret == 0 && strchr(path, '#') == NULL) {
                if (why != NULL) {
                        *why = NAME_ERR_NO_POUND;
                        *what = '#';
                }
                return (-1);
        }

        return (ret);
}

/*
 * Assert path is a valid snapshot name
 */
int
snapshot_namecheck(const char *path, namecheck_err_t *why, char *what)
{
        int ret = entity_namecheck(path, why, what);

        if (ret == 0 && strchr(path, '@') == NULL) {
                if (why != NULL) {
                        *why = NAME_ERR_NO_AT;
                        *what = '@';
                }
                return (-1);
        }

        return (ret);
}

/*
 * mountpoint names must be of the following form:
 *
 *      /[component][/]*[component][/]
 *
 * Returns 0 on success, -1 on error.
 */
int
mountpoint_namecheck(const char *path, namecheck_err_t *why)
{
        const char *start, *end;

        /*
         * Make sure none of the mountpoint component names are too long.
         * If a component name is too long then the mkdir of the mountpoint
         * will fail but then the mountpoint property will be set to a value
         * that can never be mounted.  Better to fail before setting the prop.
         * Extra slashes are OK, they will be tossed by the mountpoint mkdir.
         */

        if (path == NULL || *path != '/') {
                if (why)
                        *why = NAME_ERR_LEADING_SLASH;
                return (-1);
        }

        /* Skip leading slash  */
        start = &path[1];
        do {
                end = start;
                while (*end != '/' && *end != '\0')
                        end++;

                if (end - start >= ZFS_MAX_DATASET_NAME_LEN) {
                        if (why)
                                *why = NAME_ERR_TOOLONG;
                        return (-1);
                }
                start = end + 1;

        } while (*end != '\0');

        return (0);
}

/*
 * For pool names, we have the same set of valid characters as described in
 * dataset names, with the additional restriction that the pool name must begin
 * with a letter.  The pool names 'raidz' and 'mirror' are also reserved names
 * that cannot be used.
 *
 * Returns 0 on success, -1 on error.
 */
int
pool_namecheck(const char *pool, namecheck_err_t *why, char *what)
{
        const char *c;

        /*
         * Make sure the name is not too long.
         * If we're creating a pool with version >= SPA_VERSION_DSL_SCRUB (v11)
         * we need to account for additional space needed by the origin ds which
         * will also be snapshotted: "poolname"+"/"+"$ORIGIN"+"@"+"$ORIGIN".
         * Play it safe and enforce this limit even if the pool version is < 11
         * so it can be upgraded without issues.
         */
        if (strlen(pool) >= (ZFS_MAX_DATASET_NAME_LEN - 2 -
            strlen(ORIGIN_DIR_NAME) * 2)) {
                if (why)
                        *why = NAME_ERR_TOOLONG;
                return (-1);
        }

        c = pool;
        while (*c != '\0') {
                if (!valid_char(*c)) {
                        if (why) {
                                *why = NAME_ERR_INVALCHAR;
                                *what = *c;
                        }
                        return (-1);
                }
                c++;
        }

        if (!(*pool >= 'a' && *pool <= 'z') &&
            !(*pool >= 'A' && *pool <= 'Z')) {
                if (why)
                        *why = NAME_ERR_NOLETTER;
                return (-1);
        }

        if (strcmp(pool, "mirror") == 0 ||
            strcmp(pool, "raidz") == 0 ||
            strcmp(pool, "draid") == 0) {
                if (why)
                        *why = NAME_ERR_RESERVED;
                return (-1);
        }

        return (0);
}

EXPORT_SYMBOL(entity_namecheck);
EXPORT_SYMBOL(pool_namecheck);
EXPORT_SYMBOL(dataset_namecheck);
EXPORT_SYMBOL(bookmark_namecheck);
EXPORT_SYMBOL(snapshot_namecheck);
EXPORT_SYMBOL(zfs_component_namecheck);
EXPORT_SYMBOL(dataset_nestcheck);
EXPORT_SYMBOL(get_dataset_depth);
EXPORT_SYMBOL(zfs_max_dataset_nesting);

ZFS_MODULE_PARAM(zfs, zfs_, max_dataset_nesting, INT, ZMOD_RW,
        "Limit to the amount of nesting a path can have. Defaults to 50.");