xattr.c

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/*
 * 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);
}