/*
 * Copyright (C) 2007 Red Hat.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/init.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/rwsem.h>
#include <linux/xattr.h>
#include <linux/security.h>
#include "ctree.h"
#include "btrfs_inode.h"
#include "transaction.h"
#include "xattr.h"
#include "disk-io.h"


ssize_t __btrfs_getxattr(struct inode *inode, const char *name,
                                void *buffer, size_t size)
{
        struct btrfs_dir_item *di;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        int ret = 0;
        unsigned long data_ptr;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        /* lookup the xattr by name */
        di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(inode), name,
                                strlen(name), 0);
        if (!di) {
                ret = -ENODATA;
                goto out;
        } else if (IS_ERR(di)) {
                ret = PTR_ERR(di);
                goto out;
        }

        leaf = path->nodes[0];
        /* if size is 0, that means we want the size of the attr */
        if (!size) {
                ret = btrfs_dir_data_len(leaf, di);
                goto out;
        }

        /* now get the data out of our dir_item */
        if (btrfs_dir_data_len(leaf, di) > size) {
                ret = -ERANGE;
                goto out;
        }

        /*
         * The way things are packed into the leaf is like this
         * |struct btrfs_dir_item|name|data|
         * where name is the xattr name, so security.foo, and data is the
         * content of the xattr.  data_ptr points to the location in memory
         * where the data starts in the in memory leaf
         */
        data_ptr = (unsigned long)((char *)(di + 1) +
                                   btrfs_dir_name_len(leaf, di));
        read_extent_buffer(leaf, buffer, data_ptr,
                           btrfs_dir_data_len(leaf, di));
        ret = btrfs_dir_data_len(leaf, di);

out:
        btrfs_free_path(path);
        return ret;
}

static int do_setxattr(struct btrfs_trans_handle *trans,
                       struct inode *inode, const char *name,
                       const void *value, size_t size, int flags)
{
        struct btrfs_dir_item *di;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_path *path;
        size_t name_len = strlen(name);
        int ret = 0;

        if (name_len + size > BTRFS_MAX_XATTR_SIZE(root))
                return -ENOSPC;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        if (flags & XATTR_REPLACE) {
                di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode), name,
                                        name_len, -1);
                if (IS_ERR(di)) {
                        ret = PTR_ERR(di);
                        goto out;
                } else if (!di) {
                        ret = -ENODATA;
                        goto out;
                }
                ret = btrfs_delete_one_dir_name(trans, root, path, di);
                if (ret)
                        goto out;
                btrfs_release_path(path);

                /*
                 * remove the attribute
                 */
                if (!value)
                        goto out;
        }

again:
        ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(inode),
                                      name, name_len, value, size);
        /*
         * If we're setting an xattr to a new value but the new value is say
         * exactly BTRFS_MAX_XATTR_SIZE, we could end up with EOVERFLOW getting
         * back from split_leaf.  This is because it thinks we'll be extending
         * the existing item size, but we're asking for enough space to add the
         * item itself.  So if we get EOVERFLOW just set ret to EEXIST and let
         * the rest of the function figure it out.
         */
        if (ret == -EOVERFLOW)
                ret = -EEXIST;

        if (ret == -EEXIST) {
                if (flags & XATTR_CREATE)
                        goto out;
                /*
                 * We can't use the path we already have since we won't have the
                 * proper locking for a delete, so release the path and
                 * re-lookup to delete the thing.
                 */
                btrfs_release_path(path);
                di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode),
                                        name, name_len, -1);
                if (IS_ERR(di)) {
                        ret = PTR_ERR(di);
                        goto out;
                } else if (!di) {
                        /* Shouldn't happen but just in case... */
                        btrfs_release_path(path);
                        goto again;
                }

                ret = btrfs_delete_one_dir_name(trans, root, path, di);
                if (ret)
                        goto out;

                /*
                 * We have a value to set, so go back and try to insert it now.
                 */
                if (value) {
                        btrfs_release_path(path);
                        goto again;
                }
        }
out:
        btrfs_free_path(path);
        return ret;
}

/*
 * @value: "" makes the attribute to empty, NULL removes it
 */
int __btrfs_setxattr(struct btrfs_trans_handle *trans,
                     struct inode *inode, const char *name,
                     const void *value, size_t size, int flags)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret;

        if (trans)
                return do_setxattr(trans, inode, name, value, size, flags);

        trans = btrfs_start_transaction(root, 2);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        ret = do_setxattr(trans, inode, name, value, size, flags);
        if (ret)
                goto out;

        inode_inc_iversion(inode);
        inode->i_ctime = CURRENT_TIME;
        ret = btrfs_update_inode(trans, root, inode);
        BUG_ON(ret);
out:
        btrfs_end_transaction(trans, root);
        return ret;
}

ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
{
        struct btrfs_key key, found_key;
        struct inode *inode = dentry->d_inode;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_dir_item *di;
        int ret = 0, slot;
        size_t total_size = 0, size_left = size;
        unsigned long name_ptr;
        size_t name_len;

        /*
         * ok we want all objects associated with this id.
         * NOTE: we set key.offset = 0; because we want to start with the
         * first xattr that we find and walk forward
         */
        key.objectid = btrfs_ino(inode);
        btrfs_set_key_type(&key, BTRFS_XATTR_ITEM_KEY);
        key.offset = 0;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;
        path->reada = 2;

        /* search for our xattrs */
        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
                goto err;

        while (1) {
                leaf = path->nodes[0];
                slot = path->slots[0];

                /* this is where we start walking through the path */
                if (slot >= btrfs_header_nritems(leaf)) {
                        /*
                         * if we've reached the last slot in this leaf we need
                         * to go to the next leaf and reset everything
                         */
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0)
                                goto err;
                        else if (ret > 0)
                                break;
                        continue;
                }

                btrfs_item_key_to_cpu(leaf, &found_key, slot);

                /* check to make sure this item is what we want */
                if (found_key.objectid != key.objectid)
                        break;
                if (btrfs_key_type(&found_key) != BTRFS_XATTR_ITEM_KEY)
                        break;

                di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
                if (verify_dir_item(root, leaf, di))
                        continue;

                name_len = btrfs_dir_name_len(leaf, di);
                total_size += name_len + 1;

                /* we are just looking for how big our buffer needs to be */
                if (!size)
                        goto next;

                if (!buffer || (name_len + 1) > size_left) {
                        ret = -ERANGE;
                        goto err;
                }

                name_ptr = (unsigned long)(di + 1);
                read_extent_buffer(leaf, buffer, name_ptr, name_len);
                buffer[name_len] = '\0';

                size_left -= name_len + 1;
                buffer += name_len + 1;
next:
                path->slots[0]++;
        }
        ret = total_size;

err:
        btrfs_free_path(path);

        return ret;
}

/*
 * List of handlers for synthetic system.* attributes.  All real ondisk
 * attributes are handled directly.
 */
const struct xattr_handler *btrfs_xattr_handlers[] = {
#ifdef CONFIG_BTRFS_FS_POSIX_ACL
        &btrfs_xattr_acl_access_handler,
        &btrfs_xattr_acl_default_handler,
#endif
        NULL,
};

/*
 * Check if the attribute is in a supported namespace.
 *
 * This applied after the check for the synthetic attributes in the system
 * namespace.
 */
static bool btrfs_is_valid_xattr(const char *name)
{
        return !strncmp(name, XATTR_SECURITY_PREFIX,
                        XATTR_SECURITY_PREFIX_LEN) ||
               !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN) ||
               !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
               !strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN);
}

ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
                       void *buffer, size_t size)
{
        /*
         * If this is a request for a synthetic attribute in the system.*
         * namespace use the generic infrastructure to resolve a handler
         * for it via sb->s_xattr.
         */
        if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
                return generic_getxattr(dentry, name, buffer, size);

        if (!btrfs_is_valid_xattr(name))
                return -EOPNOTSUPP;
        return __btrfs_getxattr(dentry->d_inode, name, buffer, size);
}

int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
                   size_t size, int flags)
{
        struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;

        /*
         * The permission on security.* and system.* is not checked
         * in permission().
         */
        if (btrfs_root_readonly(root))
                return -EROFS;

        /*
         * If this is a request for a synthetic attribute in the system.*
         * namespace use the generic infrastructure to resolve a handler
         * for it via sb->s_xattr.
         */
        if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
                return generic_setxattr(dentry, name, value, size, flags);

        if (!btrfs_is_valid_xattr(name))
                return -EOPNOTSUPP;

        if (size == 0)
                value = "";  /* empty EA, do not remove */

        return __btrfs_setxattr(NULL, dentry->d_inode, name, value, size,
                                flags);
}

int btrfs_removexattr(struct dentry *dentry, const char *name)
{
        struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;

        /*
         * The permission on security.* and system.* is not checked
         * in permission().
         */
        if (btrfs_root_readonly(root))
                return -EROFS;

        /*
         * If this is a request for a synthetic attribute in the system.*
         * namespace use the generic infrastructure to resolve a handler
         * for it via sb->s_xattr.
         */
        if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
                return generic_removexattr(dentry, name);

        if (!btrfs_is_valid_xattr(name))
                return -EOPNOTSUPP;

        return __btrfs_setxattr(NULL, dentry->d_inode, name, NULL, 0,
                                XATTR_REPLACE);
}

int btrfs_initxattrs(struct inode *inode, const struct xattr *xattr_array,
                     void *fs_info)
{
        const struct xattr *xattr;
        struct btrfs_trans_handle *trans = fs_info;
        char *name;
        int err = 0;

        for (xattr = xattr_array; xattr->name != NULL; xattr++) {
                name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
                               strlen(xattr->name) + 1, GFP_NOFS);
                if (!name) {
                        err = -ENOMEM;
                        break;
                }
                strcpy(name, XATTR_SECURITY_PREFIX);
                strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
                err = __btrfs_setxattr(trans, inode, name,
                                       xattr->value, xattr->value_len, 0);
                kfree(name);
                if (err < 0)
                        break;
        }
        return err;
}

int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
                              struct inode *inode, struct inode *dir,
                              const struct qstr *qstr)
{
        return security_inode_init_security(inode, dir, qstr,
                                            &btrfs_initxattrs, trans);
}