xfs_acl.c

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/*
 * Copyright (c) 2008, Christoph Hellwig
 * 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 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would 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 the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_acl.h"
#include "xfs_attr.h"
#include "xfs_bmap_btree.h"
#include "xfs_inode.h"
#include "xfs_vnodeops.h"
#include "xfs_trace.h"
#include <linux/slab.h>
#include <linux/xattr.h>
#include <linux/posix_acl_xattr.h>


/*
 * Locking scheme:
 *  - all ACL updates are protected by inode->i_mutex, which is taken before
 *    calling into this file.
 */

STATIC struct posix_acl *
xfs_acl_from_disk(struct xfs_acl *aclp)
{
    struct posix_acl_entry *acl_e;
    struct posix_acl *acl;
    struct xfs_acl_entry *ace;
    unsigned int count, i;

    count = be32_to_cpu(aclp->acl_cnt);
    if (count > XFS_ACL_MAX_ENTRIES)
        return ERR_PTR(-EFSCORRUPTED);

    acl = posix_acl_alloc(count, GFP_KERNEL);
    if (!acl)
        return ERR_PTR(-ENOMEM);

    for (i = 0; i < count; i++) {
        acl_e = &acl->a_entries[i];
        ace = &aclp->acl_entry[i];

        /*
         * The tag is 32 bits on disk and 16 bits in core.
         *
         * Because every access to it goes through the core
         * format first this is not a problem.
         */
        acl_e->e_tag = be32_to_cpu(ace->ae_tag);
        acl_e->e_perm = be16_to_cpu(ace->ae_perm);

        switch (acl_e->e_tag) {
        case ACL_USER:
        case ACL_GROUP:
            acl_e->e_id = be32_to_cpu(ace->ae_id);
            break;
        case ACL_USER_OBJ:
        case ACL_GROUP_OBJ:
        case ACL_MASK:
        case ACL_OTHER:
            acl_e->e_id = ACL_UNDEFINED_ID;
            break;
        default:
            goto fail;
        }
    }
    return acl;

fail:
    posix_acl_release(acl);
    return ERR_PTR(-EINVAL);
}

STATIC void
xfs_acl_to_disk(struct xfs_acl *aclp, const struct posix_acl *acl)
{
    const struct posix_acl_entry *acl_e;
    struct xfs_acl_entry *ace;
    int i;

    aclp->acl_cnt = cpu_to_be32(acl->a_count);
    for (i = 0; i < acl->a_count; i++) {
        ace = &aclp->acl_entry[i];
        acl_e = &acl->a_entries[i];

        ace->ae_tag = cpu_to_be32(acl_e->e_tag);
        ace->ae_id = cpu_to_be32(acl_e->e_id);
        ace->ae_perm = cpu_to_be16(acl_e->e_perm);
    }
}

struct posix_acl *
xfs_get_acl(struct inode *inode, int type)
{
    struct xfs_inode *ip = XFS_I(inode);
    struct posix_acl *acl;
    struct xfs_acl *xfs_acl;
    int len = sizeof(struct xfs_acl);
    unsigned char *ea_name;
    int error;

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

    trace_xfs_get_acl(ip);

    switch (type) {
    case ACL_TYPE_ACCESS:
        ea_name = SGI_ACL_FILE;
        break;
    case ACL_TYPE_DEFAULT:
        ea_name = SGI_ACL_DEFAULT;
        break;
    default:
        BUG();
    }

    /*
     * If we have a cached ACLs value just return it, not need to
     * go out to the disk.
     */

    xfs_acl = kzalloc(sizeof(struct xfs_acl), GFP_KERNEL);
    if (!xfs_acl)
        return ERR_PTR(-ENOMEM);

    error = -xfs_attr_get(ip, ea_name, (unsigned char *)xfs_acl,
                            &len, ATTR_ROOT);
    if (error) {
        /*
         * If the attribute doesn't exist make sure we have a negative
         * cache entry, for any other error assume it is transient and
         * leave the cache entry as ACL_NOT_CACHED.
         */
        if (error == -ENOATTR) {
            acl = NULL;
            goto out_update_cache;
        }
        goto out;
    }

    acl = xfs_acl_from_disk(xfs_acl);
    if (IS_ERR(acl))
        goto out;

 out_update_cache:
    set_cached_acl(inode, type, acl);
 out:
    kfree(xfs_acl);
    return acl;
}

STATIC int
xfs_set_acl(struct inode *inode, int type, struct posix_acl *acl)
{
    struct xfs_inode *ip = XFS_I(inode);
    unsigned char *ea_name;
    int error;

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

    switch (type) {
    case ACL_TYPE_ACCESS:
        ea_name = SGI_ACL_FILE;
        break;
    case ACL_TYPE_DEFAULT:
        if (!S_ISDIR(inode->i_mode))
            return acl ? -EACCES : 0;
        ea_name = SGI_ACL_DEFAULT;
        break;
    default:
        return -EINVAL;
    }

    if (acl) {
        struct xfs_acl *xfs_acl;
        int len;

        xfs_acl = kzalloc(sizeof(struct xfs_acl), GFP_KERNEL);
        if (!xfs_acl)
            return -ENOMEM;

        xfs_acl_to_disk(xfs_acl, acl);
        len = sizeof(struct xfs_acl) -
            (sizeof(struct xfs_acl_entry) *
             (XFS_ACL_MAX_ENTRIES - acl->a_count));

        error = -xfs_attr_set(ip, ea_name, (unsigned char *)xfs_acl,
                len, ATTR_ROOT);

        kfree(xfs_acl);
    } else {
        /*
         * A NULL ACL argument means we want to remove the ACL.
         */
        error = -xfs_attr_remove(ip, ea_name, ATTR_ROOT);

        /*
         * If the attribute didn't exist to start with that's fine.
         */
        if (error == -ENOATTR)
            error = 0;
    }

    if (!error)
        set_cached_acl(inode, type, acl);
    return error;
}

static int
xfs_set_mode(struct inode *inode, umode_t mode)
{
    int error = 0;

    if (mode != inode->i_mode) {
        struct iattr iattr;

        iattr.ia_valid = ATTR_MODE | ATTR_CTIME;
        iattr.ia_mode = mode;
        iattr.ia_ctime = current_fs_time(inode->i_sb);

        error = -xfs_setattr_nonsize(XFS_I(inode), &iattr, XFS_ATTR_NOACL);
    }

    return error;
}

static int
xfs_acl_exists(struct inode *inode, unsigned char *name)
{
    int len = sizeof(struct xfs_acl);

    return (xfs_attr_get(XFS_I(inode), name, NULL, &len,
                ATTR_ROOT|ATTR_KERNOVAL) == 0);
}

int
posix_acl_access_exists(struct inode *inode)
{
    return xfs_acl_exists(inode, SGI_ACL_FILE);
}

int
posix_acl_default_exists(struct inode *inode)
{
    if (!S_ISDIR(inode->i_mode))
        return 0;
    return xfs_acl_exists(inode, SGI_ACL_DEFAULT);
}

/*
 * No need for i_mutex because the inode is not yet exposed to the VFS.
 */
int
xfs_inherit_acl(struct inode *inode, struct posix_acl *acl)
{
    umode_t mode = inode->i_mode;
    int error = 0, inherit = 0;

    if (S_ISDIR(inode->i_mode)) {
        error = xfs_set_acl(inode, ACL_TYPE_DEFAULT, acl);
        if (error)
            goto out;
    }

    error = posix_acl_create(&acl, GFP_KERNEL, &mode);
    if (error < 0)
        return error;

    /*
     * If posix_acl_create returns a positive value we need to
     * inherit a permission that can't be represented using the Unix
     * mode bits and we actually need to set an ACL.
     */
    if (error > 0)
        inherit = 1;

    error = xfs_set_mode(inode, mode);
    if (error)
        goto out;

    if (inherit)
        error = xfs_set_acl(inode, ACL_TYPE_ACCESS, acl);

out:
    posix_acl_release(acl);
    return error;
}

int
xfs_acl_chmod(struct inode *inode)
{
    struct posix_acl *acl;
    int error;

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

    acl = xfs_get_acl(inode, ACL_TYPE_ACCESS);
    if (IS_ERR(acl) || !acl)
        return PTR_ERR(acl);

    error = posix_acl_chmod(&acl, GFP_KERNEL, inode->i_mode);
    if (error)
        return error;

    error = xfs_set_acl(inode, ACL_TYPE_ACCESS, acl);
    posix_acl_release(acl);
    return error;
}

static int
xfs_xattr_acl_get(struct dentry *dentry, const char *name,
        void *value, size_t size, int type)
{
    struct posix_acl *acl;
    int error;

    acl = xfs_get_acl(dentry->d_inode, type);
    if (IS_ERR(acl))
        return PTR_ERR(acl);
    if (acl == NULL)
        return -ENODATA;

    error = posix_acl_to_xattr(&init_user_ns, acl, value, size);
    posix_acl_release(acl);

    return error;
}

static int
xfs_xattr_acl_set(struct dentry *dentry, const char *name,
        const void *value, size_t size, int flags, int type)
{
    struct inode *inode = dentry->d_inode;
    struct posix_acl *acl = NULL;
    int error = 0;

    if (flags & XATTR_CREATE)
        return -EINVAL;
    if (type == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode))
        return value ? -EACCES : 0;
    if ((current_fsuid() != inode->i_uid) && !capable(CAP_FOWNER))
        return -EPERM;

    if (!value)
        goto set_acl;

    acl = posix_acl_from_xattr(&init_user_ns, value, size);
    if (!acl) {
        /*
         * acl_set_file(3) may request that we set default ACLs with
         * zero length -- defend (gracefully) against that here.
         */
        goto out;
    }
    if (IS_ERR(acl)) {
        error = PTR_ERR(acl);
        goto out;
    }

    error = posix_acl_valid(acl);
    if (error)
        goto out_release;

    error = -EINVAL;
    if (acl->a_count > XFS_ACL_MAX_ENTRIES)
        goto out_release;

    if (type == ACL_TYPE_ACCESS) {
        umode_t mode = inode->i_mode;
        error = posix_acl_equiv_mode(acl, &mode);

        if (error <= 0) {
            posix_acl_release(acl);
            acl = NULL;

            if (error < 0)
                return error;
        }

        error = xfs_set_mode(inode, mode);
        if (error)
            goto out_release;
    }

 set_acl:
    error = xfs_set_acl(inode, type, acl);
 out_release:
    posix_acl_release(acl);
 out:
    return error;
}

const struct xattr_handler xfs_xattr_acl_access_handler = {
    .prefix = POSIX_ACL_XATTR_ACCESS,
    .flags  = ACL_TYPE_ACCESS,
    .get    = xfs_xattr_acl_get,
    .set    = xfs_xattr_acl_set,
};

const struct xattr_handler xfs_xattr_acl_default_handler = {
    .prefix = POSIX_ACL_XATTR_DEFAULT,
    .flags  = ACL_TYPE_DEFAULT,
    .get    = xfs_xattr_acl_get,
    .set    = xfs_xattr_acl_set,
};