xfs_xattr.c

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/*
 * Copyright (C) 2008 Christoph Hellwig.
 * Portions Copyright (C) 2000-2008 Silicon Graphics, Inc.
 *
 * 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_da_btree.h"
#include "xfs_bmap_btree.h"
#include "xfs_inode.h"
#include "xfs_attr.h"
#include "xfs_attr_leaf.h"
#include "xfs_acl.h"
#include "xfs_vnodeops.h"

#include <linux/posix_acl_xattr.h>
#include <linux/xattr.h>


static int
xfs_xattr_get(struct dentry *dentry, const char *name,
        void *value, size_t size, int xflags)
{
    struct xfs_inode *ip = XFS_I(dentry->d_inode);
    int error, asize = size;

    if (strcmp(name, "") == 0)
        return -EINVAL;

    /* Convert Linux syscall to XFS internal ATTR flags */
    if (!size) {
        xflags |= ATTR_KERNOVAL;
        value = NULL;
    }

    error = -xfs_attr_get(ip, (unsigned char *)name, value, &asize, xflags);
    if (error)
        return error;
    return asize;
}

static int
xfs_xattr_set(struct dentry *dentry, const char *name, const void *value,
        size_t size, int flags, int xflags)
{
    struct xfs_inode *ip = XFS_I(dentry->d_inode);

    if (strcmp(name, "") == 0)
        return -EINVAL;

    /* Convert Linux syscall to XFS internal ATTR flags */
    if (flags & XATTR_CREATE)
        xflags |= ATTR_CREATE;
    if (flags & XATTR_REPLACE)
        xflags |= ATTR_REPLACE;

    if (!value)
        return -xfs_attr_remove(ip, (unsigned char *)name, xflags);
    return -xfs_attr_set(ip, (unsigned char *)name,
                (void *)value, size, xflags);
}

static const struct xattr_handler xfs_xattr_user_handler = {
    .prefix = XATTR_USER_PREFIX,
    .flags  = 0, /* no flags implies user namespace */
    .get    = xfs_xattr_get,
    .set    = xfs_xattr_set,
};

static const struct xattr_handler xfs_xattr_trusted_handler = {
    .prefix = XATTR_TRUSTED_PREFIX,
    .flags  = ATTR_ROOT,
    .get    = xfs_xattr_get,
    .set    = xfs_xattr_set,
};

static const struct xattr_handler xfs_xattr_security_handler = {
    .prefix = XATTR_SECURITY_PREFIX,
    .flags  = ATTR_SECURE,
    .get    = xfs_xattr_get,
    .set    = xfs_xattr_set,
};

const struct xattr_handler *xfs_xattr_handlers[] = {
    &xfs_xattr_user_handler,
    &xfs_xattr_trusted_handler,
    &xfs_xattr_security_handler,
#ifdef CONFIG_XFS_POSIX_ACL
    &xfs_xattr_acl_access_handler,
    &xfs_xattr_acl_default_handler,
#endif
    NULL
};

static unsigned int xfs_xattr_prefix_len(int flags)
{
    if (flags & XFS_ATTR_SECURE)
        return sizeof("security");
    else if (flags & XFS_ATTR_ROOT)
        return sizeof("trusted");
    else
        return sizeof("user");
}

static const char *xfs_xattr_prefix(int flags)
{
    if (flags & XFS_ATTR_SECURE)
        return xfs_xattr_security_handler.prefix;
    else if (flags & XFS_ATTR_ROOT)
        return xfs_xattr_trusted_handler.prefix;
    else
        return xfs_xattr_user_handler.prefix;
}

static int
xfs_xattr_put_listent(
    struct xfs_attr_list_context *context,
    int     flags,
    unsigned char   *name,
    int     namelen,
    int     valuelen,
    unsigned char   *value)
{
    unsigned int prefix_len = xfs_xattr_prefix_len(flags);
    char *offset;
    int arraytop;

    ASSERT(context->count >= 0);

    /*
     * Only show root namespace entries if we are actually allowed to
     * see them.
     */
    if ((flags & XFS_ATTR_ROOT) && !capable(CAP_SYS_ADMIN))
        return 0;

    arraytop = context->count + prefix_len + namelen + 1;
    if (arraytop > context->firstu) {
        context->count = -1;    /* insufficient space */
        return 1;
    }
    offset = (char *)context->alist + context->count;
    strncpy(offset, xfs_xattr_prefix(flags), prefix_len);
    offset += prefix_len;
    strncpy(offset, (char *)name, namelen);         /* real name */
    offset += namelen;
    *offset = '\0';
    context->count += prefix_len + namelen + 1;
    return 0;
}

static int
xfs_xattr_put_listent_sizes(
    struct xfs_attr_list_context *context,
    int     flags,
    unsigned char   *name,
    int     namelen,
    int     valuelen,
    unsigned char   *value)
{
    context->count += xfs_xattr_prefix_len(flags) + namelen + 1;
    return 0;
}

static int
list_one_attr(const char *name, const size_t len, void *data,
        size_t size, ssize_t *result)
{
    char *p = data + *result;

    *result += len;
    if (!size)
        return 0;
    if (*result > size)
        return -ERANGE;

    strcpy(p, name);
    return 0;
}

ssize_t
xfs_vn_listxattr(struct dentry *dentry, char *data, size_t size)
{
    struct xfs_attr_list_context context;
    struct attrlist_cursor_kern cursor = { 0 };
    struct inode        *inode = dentry->d_inode;
    int         error;

    /*
     * First read the regular on-disk attributes.
     */
    memset(&context, 0, sizeof(context));
    context.dp = XFS_I(inode);
    context.cursor = &cursor;
    context.resynch = 1;
    context.alist = data;
    context.bufsize = size;
    context.firstu = context.bufsize;

    if (size)
        context.put_listent = xfs_xattr_put_listent;
    else
        context.put_listent = xfs_xattr_put_listent_sizes;

    xfs_attr_list_int(&context);
    if (context.count < 0)
        return -ERANGE;

    /*
     * Then add the two synthetic ACL attributes.
     */
    if (posix_acl_access_exists(inode)) {
        error = list_one_attr(POSIX_ACL_XATTR_ACCESS,
                strlen(POSIX_ACL_XATTR_ACCESS) + 1,
                data, size, &context.count);
        if (error)
            return error;
    }

    if (posix_acl_default_exists(inode)) {
        error = list_one_attr(POSIX_ACL_XATTR_DEFAULT,
                strlen(POSIX_ACL_XATTR_DEFAULT) + 1,
                data, size, &context.count);
        if (error)
            return error;
    }

    return context.count;
}