alistair23-linux/fs/xattr_acl.c

/*
 * linux/fs/xattr_acl.c
 *
 * Almost all from linux/fs/ext2/acl.c:
 * Copyright (C) 2001 by Andreas Gruenbacher, <a.gruenbacher@computer.org>
 */

#include <linux/export.h>
#include <linux/fs.h>
#include <linux/posix_acl_xattr.h>
#include <linux/gfp.h>
#include <linux/user_namespace.h>

/*
 * Fix up the uids and gids in posix acl extended attributes in place.
 */
static void posix_acl_fix_xattr_userns(
	struct user_namespace *to, struct user_namespace *from,
	void *value, size_t size)
{
	posix_acl_xattr_header *header = (posix_acl_xattr_header *)value;
	posix_acl_xattr_entry *entry = (posix_acl_xattr_entry *)(header+1), *end;
	int count;
	kuid_t uid;
	kgid_t gid;

	if (!value)
		return;
	if (size < sizeof(posix_acl_xattr_header))
		return;
	if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
		return;

	count = posix_acl_xattr_count(size);
	if (count < 0)
		return;
	if (count == 0)
		return;

	for (end = entry + count; entry != end; entry++) {
		switch(le16_to_cpu(entry->e_tag)) {
		case ACL_USER:
			uid = make_kuid(from, le32_to_cpu(entry->e_id));
			entry->e_id = cpu_to_le32(from_kuid(to, uid));
			break;
		case ACL_GROUP:
			gid = make_kgid(from, le32_to_cpu(entry->e_id));
			entry->e_id = cpu_to_le32(from_kuid(to, uid));
			break;
		default:
			break;
		}
	}
}

void posix_acl_fix_xattr_from_user(void *value, size_t size)
{
	struct user_namespace *user_ns = current_user_ns();
	if (user_ns == &init_user_ns)
		return;
	posix_acl_fix_xattr_userns(&init_user_ns, user_ns, value, size);
}

void posix_acl_fix_xattr_to_user(void *value, size_t size)
{
	struct user_namespace *user_ns = current_user_ns();
	if (user_ns == &init_user_ns)
		return;
	posix_acl_fix_xattr_userns(user_ns, &init_user_ns, value, size);
}

/*
 * Convert from extended attribute to in-memory representation.
 */
struct posix_acl *
posix_acl_from_xattr(struct user_namespace *user_ns,
		     const void *value, size_t size)
{
	posix_acl_xattr_header *header = (posix_acl_xattr_header *)value;
	posix_acl_xattr_entry *entry = (posix_acl_xattr_entry *)(header+1), *end;
	int count;
	struct posix_acl *acl;
	struct posix_acl_entry *acl_e;

	if (!value)
		return NULL;
	if (size < sizeof(posix_acl_xattr_header))
		 return ERR_PTR(-EINVAL);
	if (header->a_version != cpu_to_le32(POSIX_ACL_XATTR_VERSION))
		return ERR_PTR(-EOPNOTSUPP);

	count = posix_acl_xattr_count(size);
	if (count < 0)
		return ERR_PTR(-EINVAL);
	if (count == 0)
		return NULL;
	
	acl = posix_acl_alloc(count, GFP_NOFS);
	if (!acl)
		return ERR_PTR(-ENOMEM);
	acl_e = acl->a_entries;
	
	for (end = entry + count; entry != end; acl_e++, entry++) {
		acl_e->e_tag  = le16_to_cpu(entry->e_tag);
		acl_e->e_perm = le16_to_cpu(entry->e_perm);

		switch(acl_e->e_tag) {
			case ACL_USER_OBJ:
			case ACL_GROUP_OBJ:
			case ACL_MASK:
			case ACL_OTHER:
				break;

			case ACL_USER:
				acl_e->e_uid =
					make_kuid(user_ns,
						  le32_to_cpu(entry->e_id));
				if (!uid_valid(acl_e->e_uid))
					goto fail;
				break;
			case ACL_GROUP:
				acl_e->e_gid =
					make_kgid(user_ns,
						  le32_to_cpu(entry->e_id));
				if (!gid_valid(acl_e->e_gid))
					goto fail;
				break;

			default:
				goto fail;
		}
	}
	return acl;

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

/*
 * Convert from in-memory to extended attribute representation.
 */
int
posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl,
		   void *buffer, size_t size)
{
	posix_acl_xattr_header *ext_acl = (posix_acl_xattr_header *)buffer;
	posix_acl_xattr_entry *ext_entry = ext_acl->a_entries;
	int real_size, n;

	real_size = posix_acl_xattr_size(acl->a_count);
	if (!buffer)
		return real_size;
	if (real_size > size)
		return -ERANGE;
	
	ext_acl->a_version = cpu_to_le32(POSIX_ACL_XATTR_VERSION);

	for (n=0; n < acl->a_count; n++, ext_entry++) {
		const struct posix_acl_entry *acl_e = &acl->a_entries[n];
		ext_entry->e_tag  = cpu_to_le16(acl_e->e_tag);
		ext_entry->e_perm = cpu_to_le16(acl_e->e_perm);
		switch(acl_e->e_tag) {
		case ACL_USER:
			ext_entry->e_id =
				cpu_to_le32(from_kuid(user_ns, acl_e->e_uid));
			break;
		case ACL_GROUP:
			ext_entry->e_id =
				cpu_to_le32(from_kgid(user_ns, acl_e->e_gid));
			break;
		default:
			ext_entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
			break;
		}
	}
	return real_size;
}
EXPORT_SYMBOL (posix_acl_to_xattr);