acl.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/fs.h>
#include <linux/string.h>
#include <linux/xattr.h>
#include <linux/posix_acl_xattr.h>
#include <linux/posix_acl.h>
#include <linux/sched.h>
#include <linux/slab.h>

#include "ctree.h"
#include "btrfs_inode.h"
#include "xattr.h"

struct posix_acl *btrfs_get_acl(struct inode *inode, int type)
{
    int size;
    const char *name;
    char *value = NULL;
    struct posix_acl *acl;

    if (!IS_POSIXACL(inode))
        return NULL;

    acl = get_cached_acl(inode, type);
    if (acl != ACL_NOT_CACHED)
        return acl;

    switch (type) {
    case ACL_TYPE_ACCESS:
        name = POSIX_ACL_XATTR_ACCESS;
        break;
    case ACL_TYPE_DEFAULT:
        name = POSIX_ACL_XATTR_DEFAULT;
        break;
    default:
        BUG();
    }

    size = __btrfs_getxattr(inode, name, "", 0);
    if (size > 0) {
        value = kzalloc(size, GFP_NOFS);
        if (!value)
            return ERR_PTR(-ENOMEM);
        size = __btrfs_getxattr(inode, name, value, size);
    }
    if (size > 0) {
        acl = posix_acl_from_xattr(&init_user_ns, value, size);
    } else if (size == -ENOENT || size == -ENODATA || size == 0) {
        /* FIXME, who returns -ENOENT?  I think nobody */
        acl = NULL;
    } else {
        acl = ERR_PTR(-EIO);
    }
    kfree(value);

    if (!IS_ERR(acl))
        set_cached_acl(inode, type, acl);

    return acl;
}

static int btrfs_xattr_acl_get(struct dentry *dentry, const char *name,
        void *value, size_t size, int type)
{
    struct posix_acl *acl;
    int ret = 0;

    if (!IS_POSIXACL(dentry->d_inode))
        return -EOPNOTSUPP;

    acl = btrfs_get_acl(dentry->d_inode, type);

    if (IS_ERR(acl))
        return PTR_ERR(acl);
    if (acl == NULL)
        return -ENODATA;
    ret = posix_acl_to_xattr(&init_user_ns, acl, value, size);
    posix_acl_release(acl);

    return ret;
}

/*
 * Needs to be called with fs_mutex held
 */
static int btrfs_set_acl(struct btrfs_trans_handle *trans,
             struct inode *inode, struct posix_acl *acl, int type)
{
    int ret, size = 0;
    const char *name;
    char *value = NULL;

    if (acl) {
        ret = posix_acl_valid(acl);
        if (ret < 0)
            return ret;
        ret = 0;
    }

    switch (type) {
    case ACL_TYPE_ACCESS:
        name = POSIX_ACL_XATTR_ACCESS;
        if (acl) {
            ret = posix_acl_equiv_mode(acl, &inode->i_mode);
            if (ret < 0)
                return ret;
        }
        ret = 0;
        break;
    case ACL_TYPE_DEFAULT:
        if (!S_ISDIR(inode->i_mode))
            return acl ? -EINVAL : 0;
        name = POSIX_ACL_XATTR_DEFAULT;
        break;
    default:
        return -EINVAL;
    }

    if (acl) {
        size = posix_acl_xattr_size(acl->a_count);
        value = kmalloc(size, GFP_NOFS);
        if (!value) {
            ret = -ENOMEM;
            goto out;
        }

        ret = posix_acl_to_xattr(&init_user_ns, acl, value, size);
        if (ret < 0)
            goto out;
    }

    ret = __btrfs_setxattr(trans, inode, name, value, size, 0);
out:
    kfree(value);

    if (!ret)
        set_cached_acl(inode, type, acl);

    return ret;
}

static int btrfs_xattr_acl_set(struct dentry *dentry, const char *name,
        const void *value, size_t size, int flags, int type)
{
    int ret;
    struct posix_acl *acl = NULL;

    if (!inode_owner_or_capable(dentry->d_inode))
        return -EPERM;

    if (!IS_POSIXACL(dentry->d_inode))
        return -EOPNOTSUPP;

    if (value) {
        acl = posix_acl_from_xattr(&init_user_ns, value, size);
        if (IS_ERR(acl))
            return PTR_ERR(acl);

        if (acl) {
            ret = posix_acl_valid(acl);
            if (ret)
                goto out;
        }
    }

    ret = btrfs_set_acl(NULL, dentry->d_inode, acl, type);
out:
    posix_acl_release(acl);

    return ret;
}

/*
 * btrfs_init_acl is already generally called under fs_mutex, so the locking
 * stuff has been fixed to work with that.  If the locking stuff changes, we
 * need to re-evaluate the acl locking stuff.
 */
int btrfs_init_acl(struct btrfs_trans_handle *trans,
           struct inode *inode, struct inode *dir)
{
    struct posix_acl *acl = NULL;
    int ret = 0;

    /* this happens with subvols */
    if (!dir)
        return 0;

    if (!S_ISLNK(inode->i_mode)) {
        if (IS_POSIXACL(dir)) {
            acl = btrfs_get_acl(dir, ACL_TYPE_DEFAULT);
            if (IS_ERR(acl))
                return PTR_ERR(acl);
        }

        if (!acl)
            inode->i_mode &= ~current_umask();
    }

    if (IS_POSIXACL(dir) && acl) {
        if (S_ISDIR(inode->i_mode)) {
            ret = btrfs_set_acl(trans, inode, acl,
                        ACL_TYPE_DEFAULT);
            if (ret)
                goto failed;
        }
        ret = posix_acl_create(&acl, GFP_NOFS, &inode->i_mode);
        if (ret < 0)
            return ret;

        if (ret > 0) {
            /* we need an acl */
            ret = btrfs_set_acl(trans, inode, acl, ACL_TYPE_ACCESS);
        } else {
            cache_no_acl(inode);
        }
    } else {
        cache_no_acl(inode);
    }
failed:
    posix_acl_release(acl);

    return ret;
}

int btrfs_acl_chmod(struct inode *inode)
{
    struct posix_acl *acl;
    int ret = 0;

    if (S_ISLNK(inode->i_mode))
        return -EOPNOTSUPP;

    if (!IS_POSIXACL(inode))
        return 0;

    acl = btrfs_get_acl(inode, ACL_TYPE_ACCESS);
    if (IS_ERR_OR_NULL(acl))
        return PTR_ERR(acl);

    ret = posix_acl_chmod(&acl, GFP_KERNEL, inode->i_mode);
    if (ret)
        return ret;
    ret = btrfs_set_acl(NULL, inode, acl, ACL_TYPE_ACCESS);
    posix_acl_release(acl);
    return ret;
}

const struct xattr_handler btrfs_xattr_acl_default_handler = {
    .prefix = POSIX_ACL_XATTR_DEFAULT,
    .flags  = ACL_TYPE_DEFAULT,
    .get    = btrfs_xattr_acl_get,
    .set    = btrfs_xattr_acl_set,
};

const struct xattr_handler btrfs_xattr_acl_access_handler = {
    .prefix = POSIX_ACL_XATTR_ACCESS,
    .flags  = ACL_TYPE_ACCESS,
    .get    = btrfs_xattr_acl_get,
    .set    = btrfs_xattr_acl_set,
};