generic_acl.c

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/*
 * (C) 2005 Andreas Gruenbacher <[email protected]>
 *
 * This file is released under the GPL.
 *
 * Generic ACL support for in-memory filesystems.
 */

#include <linux/sched.h>
#include <linux/gfp.h>
#include <linux/fs.h>
#include <linux/generic_acl.h>
#include <linux/posix_acl.h>
#include <linux/posix_acl_xattr.h>


static size_t
generic_acl_list(struct dentry *dentry, char *list, size_t list_size,
        const char *name, size_t name_len, int type)
{
    struct posix_acl *acl;
    const char *xname;
    size_t size;

    acl = get_cached_acl(dentry->d_inode, type);
    if (!acl)
        return 0;
    posix_acl_release(acl);

    switch (type) {
    case ACL_TYPE_ACCESS:
        xname = POSIX_ACL_XATTR_ACCESS;
        break;
    case ACL_TYPE_DEFAULT:
        xname = POSIX_ACL_XATTR_DEFAULT;
        break;
    default:
        return 0;
    }
    size = strlen(xname) + 1;
    if (list && size <= list_size)
        memcpy(list, xname, size);
    return size;
}

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

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

    acl = get_cached_acl(dentry->d_inode, type);
    if (!acl)
        return -ENODATA;
    error = posix_acl_to_xattr(&init_user_ns, acl, buffer, size);
    posix_acl_release(acl);

    return error;
}

static int
generic_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;

    if (strcmp(name, "") != 0)
        return -EINVAL;
    if (S_ISLNK(inode->i_mode))
        return -EOPNOTSUPP;
    if (!inode_owner_or_capable(inode))
        return -EPERM;
    if (value) {
        acl = posix_acl_from_xattr(&init_user_ns, value, size);
        if (IS_ERR(acl))
            return PTR_ERR(acl);
    }
    if (acl) {
        error = posix_acl_valid(acl);
        if (error)
            goto failed;
        switch (type) {
        case ACL_TYPE_ACCESS:
            error = posix_acl_equiv_mode(acl, &inode->i_mode);
            if (error < 0)
                goto failed;
            inode->i_ctime = CURRENT_TIME;
            if (error == 0) {
                posix_acl_release(acl);
                acl = NULL;
            }
            break;
        case ACL_TYPE_DEFAULT:
            if (!S_ISDIR(inode->i_mode)) {
                error = -EINVAL;
                goto failed;
            }
            break;
        }
    }
    set_cached_acl(inode, type, acl);
    error = 0;
failed:
    posix_acl_release(acl);
    return error;
}

int
generic_acl_init(struct inode *inode, struct inode *dir)
{
    struct posix_acl *acl = NULL;
    int error;

    if (!S_ISLNK(inode->i_mode))
        acl = get_cached_acl(dir, ACL_TYPE_DEFAULT);
    if (acl) {
        if (S_ISDIR(inode->i_mode))
            set_cached_acl(inode, ACL_TYPE_DEFAULT, acl);
        error = posix_acl_create(&acl, GFP_KERNEL, &inode->i_mode);
        if (error < 0)
            return error;
        if (error > 0)
            set_cached_acl(inode, ACL_TYPE_ACCESS, acl);
    } else {
        inode->i_mode &= ~current_umask();
    }
    error = 0;

    posix_acl_release(acl);
    return error;
}

int
generic_acl_chmod(struct inode *inode)
{
    struct posix_acl *acl;
    int error = 0;

    if (S_ISLNK(inode->i_mode))
        return -EOPNOTSUPP;
    acl = get_cached_acl(inode, ACL_TYPE_ACCESS);
    if (acl) {
        error = posix_acl_chmod(&acl, GFP_KERNEL, inode->i_mode);
        if (error)
            return error;
        set_cached_acl(inode, ACL_TYPE_ACCESS, acl);
        posix_acl_release(acl);
    }
    return error;
}

const struct xattr_handler generic_acl_access_handler = {
    .prefix = POSIX_ACL_XATTR_ACCESS,
    .flags  = ACL_TYPE_ACCESS,
    .list   = generic_acl_list,
    .get    = generic_acl_get,
    .set    = generic_acl_set,
};

const struct xattr_handler generic_acl_default_handler = {
    .prefix = POSIX_ACL_XATTR_DEFAULT,
    .flags  = ACL_TYPE_DEFAULT,
    .list   = generic_acl_list,
    .get    = generic_acl_get,
    .set    = generic_acl_set,
};