// SPDX-License-Identifier: GPL-2.0-only

#include <linux/fs.h>
#include <linux/module.h>
#include <linux/namei.h>
#include <linux/fs_context.h>
#include <linux/fs_parser.h>
#include <linux/posix_acl_xattr.h>
#include <linux/seq_file.h>
#include <linux/xattr.h>
#include "overlayfs.h"
#include "params.h"

static bool ovl_redirect_dir_def = IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_DIR);
module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644);
MODULE_PARM_DESC(redirect_dir,
                 "Default to on or off for the redirect_dir feature");

static bool ovl_redirect_always_follow =
        IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW);
module_param_named(redirect_always_follow, ovl_redirect_always_follow,
                   bool, 0644);
MODULE_PARM_DESC(redirect_always_follow,
                 "Follow redirects even if redirect_dir feature is turned off");

static bool ovl_xino_auto_def = IS_ENABLED(CONFIG_OVERLAY_FS_XINO_AUTO);
module_param_named(xino_auto, ovl_xino_auto_def, bool, 0644);
MODULE_PARM_DESC(xino_auto,
                 "Auto enable xino feature");

static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
module_param_named(index, ovl_index_def, bool, 0644);
MODULE_PARM_DESC(index,
                 "Default to on or off for the inodes index feature");

static bool ovl_nfs_export_def = IS_ENABLED(CONFIG_OVERLAY_FS_NFS_EXPORT);
module_param_named(nfs_export, ovl_nfs_export_def, bool, 0644);
MODULE_PARM_DESC(nfs_export,
                 "Default to on or off for the NFS export feature");

static bool ovl_metacopy_def = IS_ENABLED(CONFIG_OVERLAY_FS_METACOPY);
module_param_named(metacopy, ovl_metacopy_def, bool, 0644);
MODULE_PARM_DESC(metacopy,
                 "Default to on or off for the metadata only copy up feature");

enum ovl_opt {
        Opt_lowerdir,
        Opt_lowerdir_add,
        Opt_datadir_add,
        Opt_upperdir,
        Opt_workdir,
        Opt_default_permissions,
        Opt_redirect_dir,
        Opt_index,
        Opt_uuid,
        Opt_nfs_export,
        Opt_userxattr,
        Opt_xino,
        Opt_metacopy,
        Opt_verity,
        Opt_fsync,
        Opt_volatile,
        Opt_override_creds,
};

static const struct constant_table ovl_parameter_bool[] = {
        { "on",         true  },
        { "off",        false },
        {}
};

static const struct constant_table ovl_parameter_uuid[] = {
        { "off",        OVL_UUID_OFF  },
        { "null",       OVL_UUID_NULL },
        { "auto",       OVL_UUID_AUTO },
        { "on",         OVL_UUID_ON   },
        {}
};

static const char *ovl_uuid_mode(struct ovl_config *config)
{
        return ovl_parameter_uuid[config->uuid].name;
}

static int ovl_uuid_def(void)
{
        return OVL_UUID_AUTO;
}

static const struct constant_table ovl_parameter_xino[] = {
        { "off",        OVL_XINO_OFF  },
        { "auto",       OVL_XINO_AUTO },
        { "on",         OVL_XINO_ON   },
        {}
};

const char *ovl_xino_mode(struct ovl_config *config)
{
        return ovl_parameter_xino[config->xino].name;
}

static int ovl_xino_def(void)
{
        return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF;
}

const struct constant_table ovl_parameter_redirect_dir[] = {
        { "off",        OVL_REDIRECT_OFF      },
        { "follow",     OVL_REDIRECT_FOLLOW   },
        { "nofollow",   OVL_REDIRECT_NOFOLLOW },
        { "on",         OVL_REDIRECT_ON       },
        {}
};

static const char *ovl_redirect_mode(struct ovl_config *config)
{
        return ovl_parameter_redirect_dir[config->redirect_mode].name;
}

static int ovl_redirect_mode_def(void)
{
        return ovl_redirect_dir_def       ? OVL_REDIRECT_ON :
               ovl_redirect_always_follow ? OVL_REDIRECT_FOLLOW :
                                            OVL_REDIRECT_NOFOLLOW;
}

static const struct constant_table ovl_parameter_verity[] = {
        { "off",        OVL_VERITY_OFF     },
        { "on",         OVL_VERITY_ON      },
        { "require",    OVL_VERITY_REQUIRE },
        {}
};

static const char *ovl_verity_mode(struct ovl_config *config)
{
        return ovl_parameter_verity[config->verity_mode].name;
}

static int ovl_verity_mode_def(void)
{
        return OVL_VERITY_OFF;
}

static const struct constant_table ovl_parameter_fsync[] = {
        { "volatile",   OVL_FSYNC_VOLATILE },
        { "auto",       OVL_FSYNC_AUTO     },
        { "strict",     OVL_FSYNC_STRICT   },
        {}
};

static const char *ovl_fsync_mode(struct ovl_config *config)
{
        return ovl_parameter_fsync[config->fsync_mode].name;
}

static int ovl_fsync_mode_def(void)
{
        return OVL_FSYNC_AUTO;
}

const struct fs_parameter_spec ovl_parameter_spec[] = {
        fsparam_string_empty("lowerdir",    Opt_lowerdir),
        fsparam_file_or_string("lowerdir+", Opt_lowerdir_add),
        fsparam_file_or_string("datadir+",  Opt_datadir_add),
        fsparam_file_or_string("upperdir",  Opt_upperdir),
        fsparam_file_or_string("workdir",   Opt_workdir),
        fsparam_flag("default_permissions", Opt_default_permissions),
        fsparam_enum("redirect_dir",        Opt_redirect_dir, ovl_parameter_redirect_dir),
        fsparam_enum("index",               Opt_index, ovl_parameter_bool),
        fsparam_enum("uuid",                Opt_uuid, ovl_parameter_uuid),
        fsparam_enum("nfs_export",          Opt_nfs_export, ovl_parameter_bool),
        fsparam_flag("userxattr",           Opt_userxattr),
        fsparam_enum("xino",                Opt_xino, ovl_parameter_xino),
        fsparam_enum("metacopy",            Opt_metacopy, ovl_parameter_bool),
        fsparam_enum("verity",              Opt_verity, ovl_parameter_verity),
        fsparam_enum("fsync",               Opt_fsync, ovl_parameter_fsync),
        fsparam_flag("volatile",            Opt_volatile),
        fsparam_flag_no("override_creds",   Opt_override_creds),
        {}
};

static char *ovl_next_opt(char **s)
{
        char *sbegin = *s;
        char *p;

        if (sbegin == NULL)
                return NULL;

        for (p = sbegin; *p; p++) {
                if (*p == '\\') {
                        p++;
                        if (!*p)
                                break;
                } else if (*p == ',') {
                        *p = '\0';
                        *s = p + 1;
                        return sbegin;
                }
        }
        *s = NULL;
        return sbegin;
}

static int ovl_parse_monolithic(struct fs_context *fc, void *data)
{
        return vfs_parse_monolithic_sep(fc, data, ovl_next_opt);
}

static ssize_t ovl_parse_param_split_lowerdirs(char *str)
{
        ssize_t nr_layers = 1, nr_colons = 0;
        char *s, *d;

        for (s = d = str;; s++, d++) {
                if (*s == '\\') {
                        /* keep esc chars in split lowerdir */
                        *d++ = *s++;
                } else if (*s == ':') {
                        bool next_colon = (*(s + 1) == ':');

                        nr_colons++;
                        if (nr_colons == 2 && next_colon) {
                                pr_err("only single ':' or double '::' sequences of unescaped colons in lowerdir mount option allowed.\n");
                                return -EINVAL;
                        }
                        /* count layers, not colons */
                        if (!next_colon)
                                nr_layers++;

                        *d = '\0';
                        continue;
                }

                *d = *s;
                if (!*s) {
                        /* trailing colons */
                        if (nr_colons) {
                                pr_err("unescaped trailing colons in lowerdir mount option.\n");
                                return -EINVAL;
                        }
                        break;
                }
                nr_colons = 0;
        }

        return nr_layers;
}

static int ovl_mount_dir_noesc(const char *name, struct path *path)
{
        int err = -EINVAL;

        if (!*name) {
                pr_err("empty lowerdir\n");
                goto out;
        }
        err = kern_path(name, LOOKUP_FOLLOW, path);
        if (err) {
                pr_err("failed to resolve '%s': %i\n", name, err);
                goto out;
        }
        return 0;

out:
        return err;
}

static void ovl_unescape(char *s)
{
        char *d = s;

        for (;; s++, d++) {
                if (*s == '\\')
                        s++;
                *d = *s;
                if (!*s)
                        break;
        }
}

static int ovl_mount_dir(const char *name, struct path *path)
{
        int err = -ENOMEM;
        char *tmp = kstrdup(name, GFP_KERNEL);

        if (tmp) {
                ovl_unescape(tmp);
                err = ovl_mount_dir_noesc(tmp, path);
                kfree(tmp);
        }
        return err;
}

static int ovl_mount_dir_check(struct fs_context *fc, const struct path *path,
                               enum ovl_opt layer, const char *name, bool upper)
{
        bool is_casefolded = ovl_dentry_casefolded(path->dentry);
        struct ovl_fs_context *ctx = fc->fs_private;
        struct ovl_fs *ofs = fc->s_fs_info;

        if (!d_is_dir(path->dentry))
                return invalfc(fc, "%s is not a directory", name);

        /*
         * Allow filesystems that are case-folding capable but deny composing
         * ovl stack from inconsistent case-folded directories.
         */
        if (!ctx->casefold_set) {
                ofs->casefold = is_casefolded;
                ctx->casefold_set = true;
        }

        if (ofs->casefold != is_casefolded) {
                return invalfc(fc, "case-%ssensitive directory on %s is inconsistent",
                               is_casefolded ? "in" : "", name);
        }

        if (ovl_dentry_weird(path->dentry))
                return invalfc(fc, "filesystem on %s not supported", name);

        /*
         * Check whether upper path is read-only here to report failures
         * early. Don't forget to recheck when the superblock is created
         * as the mount attributes could change.
         */
        if (upper) {
                if (path->dentry->d_flags & DCACHE_OP_REAL)
                        return invalfc(fc, "filesystem on %s not supported as upperdir", name);
                if (__mnt_is_readonly(path->mnt))
                        return invalfc(fc, "filesystem on %s is read-only", name);
        } else {
                if (ctx->lowerdir_all && layer != Opt_lowerdir)
                        return invalfc(fc, "lowerdir+ and datadir+ cannot follow lowerdir");
                if (ctx->nr_data && layer == Opt_lowerdir_add)
                        return invalfc(fc, "regular lower layers cannot follow data layers");
                if (ctx->nr == OVL_MAX_STACK)
                        return invalfc(fc, "too many lower directories, limit is %d",
                                       OVL_MAX_STACK);
        }
        return 0;
}

static int ovl_ctx_realloc_lower(struct fs_context *fc)
{
        struct ovl_fs_context *ctx = fc->fs_private;
        struct ovl_fs_context_layer *l;
        size_t nr;

        if (ctx->nr < ctx->capacity)
                return 0;

        nr = min_t(size_t, max(4096 / sizeof(*l), ctx->capacity * 2),
                   OVL_MAX_STACK);
        l = krealloc_array(ctx->lower, nr, sizeof(*l), GFP_KERNEL_ACCOUNT);
        if (!l)
                return -ENOMEM;

        ctx->lower = l;
        ctx->capacity = nr;
        return 0;
}

static void ovl_add_layer(struct fs_context *fc, enum ovl_opt layer,
                         struct path *path, char **pname)
{
        struct ovl_fs *ofs = fc->s_fs_info;
        struct ovl_config *config = &ofs->config;
        struct ovl_fs_context *ctx = fc->fs_private;
        struct ovl_fs_context_layer *l;

        switch (layer) {
        case Opt_workdir:
                swap(config->workdir, *pname);
                swap(ctx->work, *path);
                break;
        case Opt_upperdir:
                swap(config->upperdir, *pname);
                swap(ctx->upper, *path);
                break;
        case Opt_datadir_add:
                ctx->nr_data++;
                fallthrough;
        case Opt_lowerdir:
                fallthrough;
        case Opt_lowerdir_add:
                WARN_ON(ctx->nr >= ctx->capacity);
                l = &ctx->lower[ctx->nr++];
                memset(l, 0, sizeof(*l));
                swap(l->name, *pname);
                swap(l->path, *path);
                break;
        default:
                WARN_ON(1);
        }
}

static inline bool is_upper_layer(enum ovl_opt layer)
{
        return layer == Opt_upperdir || layer == Opt_workdir;
}

/* Handle non-file descriptor-based layer options that require path lookup. */
static inline int ovl_kern_path(const char *layer_name, struct path *layer_path,
                                enum ovl_opt layer)
{
        int err;

        switch (layer) {
        case Opt_upperdir:
                fallthrough;
        case Opt_workdir:
                fallthrough;
        case Opt_lowerdir:
                err = ovl_mount_dir(layer_name, layer_path);
                break;
        case Opt_lowerdir_add:
                fallthrough;
        case Opt_datadir_add:
                err = ovl_mount_dir_noesc(layer_name, layer_path);
                break;
        default:
                WARN_ON_ONCE(true);
                err = -EINVAL;
        }

        return err;
}

static int ovl_do_parse_layer(struct fs_context *fc, const char *layer_name,
                              struct path *layer_path, enum ovl_opt layer)
{
        char *name __free(kfree) = kstrdup(layer_name, GFP_KERNEL);
        bool upper;
        int err = 0;

        if (!name)
                return -ENOMEM;

        upper = is_upper_layer(layer);
        err = ovl_mount_dir_check(fc, layer_path, layer, name, upper);
        if (err)
                return err;

        if (!upper) {
                err = ovl_ctx_realloc_lower(fc);
                if (err)
                        return err;
        }

        /* Store the user provided path string in ctx to show in mountinfo */
        ovl_add_layer(fc, layer, layer_path, &name);
        return err;
}

static int ovl_parse_layer(struct fs_context *fc, struct fs_parameter *param,
                           enum ovl_opt layer)
{
        struct path layer_path __free(path_put) = {};
        int err = 0;

        switch (param->type) {
        case fs_value_is_string:
                err = ovl_kern_path(param->string, &layer_path, layer);
                if (err)
                        return err;
                err = ovl_do_parse_layer(fc, param->string, &layer_path, layer);
                break;
        case fs_value_is_file: {
                char *buf __free(kfree);
                char *layer_name;

                buf = kmalloc(PATH_MAX, GFP_KERNEL_ACCOUNT);
                if (!buf)
                        return -ENOMEM;

                layer_path = param->file->f_path;
                path_get(&layer_path);

                layer_name = d_path(&layer_path, buf, PATH_MAX);
                if (IS_ERR(layer_name))
                        return PTR_ERR(layer_name);

                err = ovl_do_parse_layer(fc, layer_name, &layer_path, layer);
                break;
        }
        default:
                WARN_ON_ONCE(true);
                err = -EINVAL;
        }

        return err;
}

static void ovl_reset_lowerdirs(struct ovl_fs_context *ctx)
{
        struct ovl_fs_context_layer *l = ctx->lower;

        // Reset old user provided lowerdir string
        kfree(ctx->lowerdir_all);
        ctx->lowerdir_all = NULL;

        for (size_t nr = 0; nr < ctx->nr; nr++, l++) {
                path_put(&l->path);
                kfree(l->name);
                l->name = NULL;
        }
        ctx->nr = 0;
        ctx->nr_data = 0;
}

/*
 * Parse lowerdir= mount option:
 *
 * e.g.: lowerdir=/lower1:/lower2:/lower3::/data1::/data2
 *     Set "/lower1", "/lower2", and "/lower3" as lower layers and
 *     "/data1" and "/data2" as data lower layers. Any existing lower
 *     layers are replaced.
 */
static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
{
        int err;
        struct ovl_fs_context *ctx = fc->fs_private;
        char *dup = NULL, *iter;
        ssize_t nr_lower, nr;
        bool data_layer = false;

        /*
         * Ensure we're backwards compatible with mount(2)
         * by allowing relative paths.
         */

        /* drop all existing lower layers */
        ovl_reset_lowerdirs(ctx);

        if (!*name)
                return 0;

        if (*name == ':') {
                pr_err("cannot append lower layer\n");
                return -EINVAL;
        }

        // Store user provided lowerdir string to show in mount options
        ctx->lowerdir_all = kstrdup(name, GFP_KERNEL);
        if (!ctx->lowerdir_all)
                return -ENOMEM;

        dup = kstrdup(name, GFP_KERNEL);
        if (!dup)
                return -ENOMEM;

        err = -EINVAL;
        nr_lower = ovl_parse_param_split_lowerdirs(dup);
        if (nr_lower < 0)
                goto out_err;

        if (nr_lower > OVL_MAX_STACK) {
                pr_err("too many lower directories, limit is %d\n", OVL_MAX_STACK);
                goto out_err;
        }

        iter = dup;
        for (nr = 0; nr < nr_lower; nr++) {
                struct path path __free(path_put) = {};

                err = ovl_kern_path(iter, &path, Opt_lowerdir);
                if (err)
                        goto out_err;

                err = ovl_do_parse_layer(fc, iter, &path, Opt_lowerdir);
                if (err)
                        goto out_err;

                if (data_layer)
                        ctx->nr_data++;

                /* Calling strchr() again would overrun. */
                if (ctx->nr == nr_lower)
                        break;

                err = -EINVAL;
                iter = strchr(iter, '\0') + 1;
                if (*iter) {
                        /*
                         * This is a regular layer so we require that
                         * there are no data layers.
                         */
                        if (ctx->nr_data > 0) {
                                pr_err("regular lower layers cannot follow data lower layers\n");
                                goto out_err;
                        }

                        data_layer = false;
                        continue;
                }

                /* This is a data lower layer. */
                data_layer = true;
                iter++;
        }
        kfree(dup);
        return 0;

out_err:
        kfree(dup);

        /* Intentionally don't realloc to a smaller size. */
        return err;
}

static int ovl_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
        int err = 0;
        struct fs_parse_result result;
        struct ovl_fs *ofs = fc->s_fs_info;
        struct ovl_config *config = &ofs->config;
        struct ovl_fs_context *ctx = fc->fs_private;
        int opt;

        if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE) {
                /*
                 * On remount overlayfs has always ignored all mount
                 * options no matter if malformed or not so for
                 * backwards compatibility we do the same here.
                 */
                if (fc->oldapi)
                        return 0;

                /*
                 * Give us the freedom to allow changing mount options
                 * with the new mount api in the future. So instead of
                 * silently ignoring everything we report a proper
                 * error. This is only visible for users of the new
                 * mount api.
                 */
                return invalfc(fc, "No changes allowed in reconfigure");
        }

        opt = fs_parse(fc, ovl_parameter_spec, param, &result);
        if (opt < 0)
                return opt;

        switch (opt) {
        case Opt_lowerdir:
                err = ovl_parse_param_lowerdir(param->string, fc);
                break;
        case Opt_lowerdir_add:
        case Opt_datadir_add:
        case Opt_upperdir:
        case Opt_workdir:
                err = ovl_parse_layer(fc, param, opt);
                break;
        case Opt_default_permissions:
                config->default_permissions = true;
                break;
        case Opt_redirect_dir:
                config->redirect_mode = result.uint_32;
                if (config->redirect_mode == OVL_REDIRECT_OFF) {
                        config->redirect_mode = ovl_redirect_always_follow ?
                                                OVL_REDIRECT_FOLLOW :
                                                OVL_REDIRECT_NOFOLLOW;
                }
                ctx->set.redirect = true;
                break;
        case Opt_index:
                config->index = result.uint_32;
                ctx->set.index = true;
                break;
        case Opt_uuid:
                config->uuid = result.uint_32;
                break;
        case Opt_nfs_export:
                config->nfs_export = result.uint_32;
                ctx->set.nfs_export = true;
                break;
        case Opt_xino:
                config->xino = result.uint_32;
                break;
        case Opt_metacopy:
                config->metacopy = result.uint_32;
                ctx->set.metacopy = true;
                break;
        case Opt_verity:
                config->verity_mode = result.uint_32;
                break;
        case Opt_fsync:
                config->fsync_mode = result.uint_32;
                break;
        case Opt_volatile:
                config->fsync_mode = OVL_FSYNC_VOLATILE;
                break;
        case Opt_userxattr:
                config->userxattr = true;
                break;
        case Opt_override_creds: {
                const struct cred *cred = NULL;

                if (result.negated) {
                        swap(cred, ofs->creator_cred);
                        put_cred(cred);
                        break;
                }

                if (!current_in_userns(fc->user_ns)) {
                        err = -EINVAL;
                        break;
                }

                cred = prepare_creds();
                if (cred)
                        swap(cred, ofs->creator_cred);
                else
                        err = -ENOMEM;

                put_cred(cred);
                break;
        }
        default:
                pr_err("unrecognized mount option \"%s\" or missing value\n",
                       param->key);
                return -EINVAL;
        }

        return err;
}

static int ovl_get_tree(struct fs_context *fc)
{
        return get_tree_nodev(fc, ovl_fill_super);
}

static inline void ovl_fs_context_free(struct ovl_fs_context *ctx)
{
        ovl_reset_lowerdirs(ctx);
        path_put(&ctx->upper);
        path_put(&ctx->work);
        kfree(ctx->lower);
        kfree(ctx);
}

static void ovl_free(struct fs_context *fc)
{
        struct ovl_fs *ofs = fc->s_fs_info;
        struct ovl_fs_context *ctx = fc->fs_private;

        /*
         * ofs is stored in the fs_context when it is initialized.
         * ofs is transferred to the superblock on a successful mount,
         * but if an error occurs before the transfer we have to free
         * it here.
         */
        if (ofs)
                ovl_free_fs(ofs);

        if (ctx)
                ovl_fs_context_free(ctx);
}

static int ovl_reconfigure(struct fs_context *fc)
{
        struct super_block *sb = fc->root->d_sb;
        struct ovl_fs *ofs = OVL_FS(sb);
        struct super_block *upper_sb;
        int ret = 0;

        if (!(fc->sb_flags & SB_RDONLY) && ovl_force_readonly(ofs))
                return -EROFS;

        if (fc->sb_flags & SB_RDONLY && !sb_rdonly(sb)) {
                upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
                if (ovl_should_sync(ofs)) {
                        down_read(&upper_sb->s_umount);
                        ret = sync_filesystem(upper_sb);
                        up_read(&upper_sb->s_umount);
                }
        }

        return ret;
}

static const struct fs_context_operations ovl_context_ops = {
        .parse_monolithic = ovl_parse_monolithic,
        .parse_param = ovl_parse_param,
        .get_tree    = ovl_get_tree,
        .reconfigure = ovl_reconfigure,
        .free        = ovl_free,
};

/*
 * This is called during fsopen() and will record the user namespace of
 * the caller in fc->user_ns since we've raised FS_USERNS_MOUNT. We'll
 * need it when we actually create the superblock to verify that the
 * process creating the superblock is in the same user namespace as
 * process that called fsopen().
 */
int ovl_init_fs_context(struct fs_context *fc)
{
        struct ovl_fs_context *ctx;
        struct ovl_fs *ofs;

        ctx = kzalloc_obj(*ctx, GFP_KERNEL_ACCOUNT);
        if (!ctx)
                return -ENOMEM;

        /*
         * By default we allocate for three lower layers. It's likely
         * that it'll cover most users.
         */
        ctx->lower = kmalloc_objs(*ctx->lower, 3, GFP_KERNEL_ACCOUNT);
        if (!ctx->lower)
                goto out_err;
        ctx->capacity = 3;

        ofs = kzalloc_obj(struct ovl_fs);
        if (!ofs)
                goto out_err;

        ofs->config.redirect_mode       = ovl_redirect_mode_def();
        ofs->config.index               = ovl_index_def;
        ofs->config.uuid                = ovl_uuid_def();
        ofs->config.nfs_export          = ovl_nfs_export_def;
        ofs->config.xino                = ovl_xino_def();
        ofs->config.metacopy            = ovl_metacopy_def;
        ofs->config.fsync_mode          = ovl_fsync_mode_def();

        fc->s_fs_info           = ofs;
        fc->fs_private          = ctx;
        fc->ops                 = &ovl_context_ops;

        mutex_init(&ofs->whiteout_lock);
        return 0;

out_err:
        ovl_fs_context_free(ctx);
        return -ENOMEM;

}

void ovl_free_fs(struct ovl_fs *ofs)
{
        struct vfsmount **mounts;
        unsigned i;

        iput(ofs->workbasedir_trap);
        iput(ofs->workdir_trap);
        dput(ofs->whiteout);
        dput(ofs->workdir);
        if (ofs->workdir_locked)
                ovl_inuse_unlock(ofs->workbasedir);
        dput(ofs->workbasedir);
        if (ofs->upperdir_locked)
                ovl_inuse_unlock(ovl_upper_mnt(ofs)->mnt_root);

        /* Reuse ofs->config.lowerdirs as a vfsmount array before freeing it */
        mounts = (struct vfsmount **) ofs->config.lowerdirs;
        for (i = 0; i < ofs->numlayer; i++) {
                iput(ofs->layers[i].trap);
                kfree(ofs->config.lowerdirs[i]);
                mounts[i] = ofs->layers[i].mnt;
        }
        kern_unmount_array(mounts, ofs->numlayer);
        kfree(ofs->layers);
        for (i = 0; i < ofs->numfs; i++)
                free_anon_bdev(ofs->fs[i].pseudo_dev);
        kfree(ofs->fs);

        kfree(ofs->config.lowerdirs);
        kfree(ofs->config.upperdir);
        kfree(ofs->config.workdir);
        if (ofs->creator_cred)
                put_cred(ofs->creator_cred);
        kfree(ofs);
}

int ovl_fs_params_verify(const struct ovl_fs_context *ctx,
                         struct ovl_config *config)
{
        struct ovl_opt_set set = ctx->set;

        /* Workdir/index are useless in non-upper mount */
        if (!config->upperdir) {
                if (config->workdir) {
                        pr_info("option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
                                config->workdir);
                        kfree(config->workdir);
                        config->workdir = NULL;
                }
                if (config->index && set.index) {
                        pr_info("option \"index=on\" is useless in a non-upper mount, ignore\n");
                        set.index = false;
                }
                config->index = false;
        }

        if (!config->upperdir && ovl_is_volatile(config)) {
                pr_info("option \"volatile\" is meaningless in a non-upper mount, ignoring it.\n");
                config->fsync_mode = ovl_fsync_mode_def();
        }

        if (!config->upperdir && config->uuid == OVL_UUID_ON) {
                pr_info("option \"uuid=on\" requires an upper fs, falling back to uuid=null.\n");
                config->uuid = OVL_UUID_NULL;
        }

        /*
         * This is to make the logic below simpler.  It doesn't make any other
         * difference, since redirect_dir=on is only used for upper.
         */
        if (!config->upperdir && config->redirect_mode == OVL_REDIRECT_FOLLOW)
                config->redirect_mode = OVL_REDIRECT_ON;

        /* metacopy -> redirect_dir dependency */
        if (config->metacopy && config->redirect_mode != OVL_REDIRECT_ON) {
                if (set.metacopy && set.redirect) {
                        pr_err("conflicting options: metacopy=on,redirect_dir=%s\n",
                               ovl_redirect_mode(config));
                        return -EINVAL;
                }
                if (set.redirect) {
                        /*
                         * There was an explicit redirect_dir=... that resulted
                         * in this conflict.
                         */
                        pr_info("disabling metacopy due to redirect_dir=%s\n",
                                ovl_redirect_mode(config));
                        config->metacopy = false;
                } else {
                        /* Automatically enable redirect otherwise. */
                        config->redirect_mode = OVL_REDIRECT_ON;
                }
        }

        /* Resolve nfs_export -> index dependency */
        if (config->nfs_export && !config->index) {
                if (!config->upperdir &&
                    config->redirect_mode != OVL_REDIRECT_NOFOLLOW) {
                        pr_info("NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
                        config->nfs_export = false;
                } else if (set.nfs_export && set.index) {
                        pr_err("conflicting options: nfs_export=on,index=off\n");
                        return -EINVAL;
                } else if (set.index) {
                        /*
                         * There was an explicit index=off that resulted
                         * in this conflict.
                         */
                        pr_info("disabling nfs_export due to index=off\n");
                        config->nfs_export = false;
                } else {
                        /* Automatically enable index otherwise. */
                        config->index = true;
                }
        }

        /* Resolve nfs_export -> !metacopy && !verity dependency */
        if (config->nfs_export && config->metacopy) {
                if (set.nfs_export && set.metacopy) {
                        pr_err("conflicting options: nfs_export=on,metacopy=on\n");
                        return -EINVAL;
                }
                if (set.metacopy) {
                        /*
                         * There was an explicit metacopy=on that resulted
                         * in this conflict.
                         */
                        pr_info("disabling nfs_export due to metacopy=on\n");
                        config->nfs_export = false;
                } else if (config->verity_mode) {
                        /*
                         * There was an explicit verity=.. that resulted
                         * in this conflict.
                         */
                        pr_info("disabling nfs_export due to verity=%s\n",
                                ovl_verity_mode(config));
                        config->nfs_export = false;
                } else {
                        /*
                         * There was an explicit nfs_export=on that resulted
                         * in this conflict.
                         */
                        pr_info("disabling metacopy due to nfs_export=on\n");
                        config->metacopy = false;
                }
        }


        /* Resolve userxattr -> !redirect && !metacopy dependency */
        if (config->userxattr) {
                if (set.redirect &&
                    config->redirect_mode != OVL_REDIRECT_NOFOLLOW) {
                        pr_err("conflicting options: userxattr,redirect_dir=%s\n",
                               ovl_redirect_mode(config));
                        return -EINVAL;
                }
                if (config->metacopy && set.metacopy) {
                        pr_err("conflicting options: userxattr,metacopy=on\n");
                        return -EINVAL;
                }
                /*
                 * Silently disable default setting of redirect and metacopy.
                 * This shall be the default in the future as well: these
                 * options must be explicitly enabled if used together with
                 * userxattr.
                 */
                config->redirect_mode = OVL_REDIRECT_NOFOLLOW;
                config->metacopy = false;
        }

        /*
         * Fail if we don't have trusted xattr capability and a feature was
         * explicitly requested that requires them.
         */
        if (!config->userxattr && !capable(CAP_SYS_ADMIN)) {
                if (set.redirect &&
                    config->redirect_mode != OVL_REDIRECT_NOFOLLOW) {
                        pr_err("redirect_dir requires permission to access trusted xattrs\n");
                        return -EPERM;
                }
                if (config->metacopy && set.metacopy) {
                        pr_err("metacopy requires permission to access trusted xattrs\n");
                        return -EPERM;
                }
                if (config->verity_mode) {
                        pr_err("verity requires permission to access trusted xattrs\n");
                        return -EPERM;
                }
                if (ctx->nr_data > 0) {
                        pr_err("lower data-only dirs require permission to access trusted xattrs\n");
                        return -EPERM;
                }
                /*
                 * Other xattr-dependent features should be disabled without
                 * great disturbance to the user in ovl_make_workdir().
                 */
        }

        return 0;
}

/**
 * ovl_show_options
 * @m: the seq_file handle
 * @dentry: The dentry to query
 *
 * Prints the mount options for a given superblock.
 * Returns zero; does not fail.
 */
int ovl_show_options(struct seq_file *m, struct dentry *dentry)
{
        struct super_block *sb = dentry->d_sb;
        struct ovl_fs *ofs = OVL_FS(sb);
        size_t nr, nr_merged_lower, nr_lower = 0;
        char **lowerdirs = ofs->config.lowerdirs;

        /*
         * lowerdirs[0] holds the colon separated list that user provided
         * with lowerdir mount option.
         * lowerdirs[1..numlayer] hold the lowerdir paths that were added
         * using the lowerdir+ and datadir+ mount options.
         * For now, we do not allow mixing the legacy lowerdir mount option
         * with the new lowerdir+ and datadir+ mount options.
         */
        if (lowerdirs[0]) {
                seq_show_option(m, "lowerdir", lowerdirs[0]);
        } else {
                nr_lower = ofs->numlayer;
                nr_merged_lower = nr_lower - ofs->numdatalayer;
        }
        for (nr = 1; nr < nr_lower; nr++) {
                if (nr < nr_merged_lower)
                        seq_show_option(m, "lowerdir+", lowerdirs[nr]);
                else
                        seq_show_option(m, "datadir+", lowerdirs[nr]);
        }
        if (ofs->config.upperdir) {
                seq_show_option(m, "upperdir", ofs->config.upperdir);
                seq_show_option(m, "workdir", ofs->config.workdir);
        }
        if (ofs->config.default_permissions)
                seq_puts(m, ",default_permissions");
        if (ofs->config.redirect_mode != ovl_redirect_mode_def())
                seq_printf(m, ",redirect_dir=%s",
                           ovl_redirect_mode(&ofs->config));
        if (ofs->config.index != ovl_index_def)
                seq_printf(m, ",index=%s", str_on_off(ofs->config.index));
        if (ofs->config.uuid != ovl_uuid_def())
                seq_printf(m, ",uuid=%s", ovl_uuid_mode(&ofs->config));
        if (ofs->config.nfs_export != ovl_nfs_export_def)
                seq_printf(m, ",nfs_export=%s",
                           str_on_off(ofs->config.nfs_export));
        if (ofs->config.xino != ovl_xino_def() && !ovl_same_fs(ofs))
                seq_printf(m, ",xino=%s", ovl_xino_mode(&ofs->config));
        if (ofs->config.metacopy != ovl_metacopy_def)
                seq_printf(m, ",metacopy=%s", str_on_off(ofs->config.metacopy));
        if (ofs->config.fsync_mode != ovl_fsync_mode_def())
                seq_printf(m, ",fsync=%s", ovl_fsync_mode(&ofs->config));
        if (ofs->config.userxattr)
                seq_puts(m, ",userxattr");
        if (ofs->config.verity_mode != ovl_verity_mode_def())
                seq_printf(m, ",verity=%s",
                           ovl_verity_mode(&ofs->config));
        return 0;
}