nfs4acl.c

linux 内核源代码

	struct posix_ace_state group;
	struct posix_ace_state other;
	struct posix_ace_state everyone;
	struct posix_ace_state mask; /* Deny unused in this case */
	struct posix_ace_state_array *users;
	struct posix_ace_state_array *groups;
};

static int
init_state(struct posix_acl_state *state, int cnt)
{
	int alloc;

	memset(state, 0, sizeof(struct posix_acl_state));
	state->empty = 1;
	/*
	 * In the worst case, each individual acl could be for a distinct
	 * named user or group, but we don't no which, so we allocate
	 * enough space for either:
	 */
	alloc = sizeof(struct posix_ace_state_array)
		+ cnt*sizeof(struct posix_ace_state);
	state->users = kzalloc(alloc, GFP_KERNEL);
	if (!state->users)
		return -ENOMEM;
	state->groups = kzalloc(alloc, GFP_KERNEL);
	if (!state->groups) {
		kfree(state->users);
		return -ENOMEM;
	}
	return 0;
}

static void
free_state(struct posix_acl_state *state) {
	kfree(state->users);
	kfree(state->groups);
}

static inline void add_to_mask(struct posix_acl_state *state, struct posix_ace_state *astate)
{
	state->mask.allow |= astate->allow;
}

/*
 * Certain bits (SYNCHRONIZE, DELETE, WRITE_OWNER, READ/WRITE_NAMED_ATTRS,
 * READ_ATTRIBUTES, READ_ACL) are currently unenforceable and don't translate
 * to traditional read/write/execute permissions.
 *
 * It's problematic to reject acls that use certain mode bits, because it
 * places the burden on users to learn the rules about which bits one
 * particular server sets, without giving the user a lot of help--we return an
 * error that could mean any number of different things.  To make matters
 * worse, the problematic bits might be introduced by some application that's
 * automatically mapping from some other acl model.
 *
 * So wherever possible we accept anything, possibly erring on the side of
 * denying more permissions than necessary.
 *
 * However we do reject *explicit* DENY's of a few bits representing
 * permissions we could never deny:
 */

static inline int check_deny(u32 mask, int isowner)
{
	if (mask & (NFS4_ACE_READ_ATTRIBUTES | NFS4_ACE_READ_ACL))
		return -EINVAL;
	if (!isowner)
		return 0;
	if (mask & (NFS4_ACE_WRITE_ATTRIBUTES | NFS4_ACE_WRITE_ACL))
		return -EINVAL;
	return 0;
}

static struct posix_acl *
posix_state_to_acl(struct posix_acl_state *state, unsigned int flags)
{
	struct posix_acl_entry *pace;
	struct posix_acl *pacl;
	int nace;
	int i, error = 0;

	/*
	 * ACLs with no ACEs are treated differently in the inheritable
	 * and effective cases: when there are no inheritable ACEs, we
	 * set a zero-length default posix acl:
	 */
	if (state->empty && (flags & NFS4_ACL_TYPE_DEFAULT)) {
		pacl = posix_acl_alloc(0, GFP_KERNEL);
		return pacl ? pacl : ERR_PTR(-ENOMEM);
	}
	/*
	 * When there are no effective ACEs, the following will end
	 * up setting a 3-element effective posix ACL with all
	 * permissions zero.
	 */
	nace = 4 + state->users->n + state->groups->n;
	pacl = posix_acl_alloc(nace, GFP_KERNEL);
	if (!pacl)
		return ERR_PTR(-ENOMEM);

	pace = pacl->a_entries;
	pace->e_tag = ACL_USER_OBJ;
	error = check_deny(state->owner.deny, 1);
	if (error)
		goto out_err;
	low_mode_from_nfs4(state->owner.allow, &pace->e_perm, flags);
	pace->e_id = ACL_UNDEFINED_ID;

	for (i=0; i < state->users->n; i++) {
		pace++;
		pace->e_tag = ACL_USER;
		error = check_deny(state->users->aces[i].perms.deny, 0);
		if (error)
			goto out_err;
		low_mode_from_nfs4(state->users->aces[i].perms.allow,
					&pace->e_perm, flags);
		pace->e_id = state->users->aces[i].uid;
		add_to_mask(state, &state->users->aces[i].perms);
	}

	pace++;
	pace->e_tag = ACL_GROUP_OBJ;
	error = check_deny(state->group.deny, 0);
	if (error)
		goto out_err;
	low_mode_from_nfs4(state->group.allow, &pace->e_perm, flags);
	pace->e_id = ACL_UNDEFINED_ID;
	add_to_mask(state, &state->group);

	for (i=0; i < state->groups->n; i++) {
		pace++;
		pace->e_tag = ACL_GROUP;
		error = check_deny(state->groups->aces[i].perms.deny, 0);
		if (error)
			goto out_err;
		low_mode_from_nfs4(state->groups->aces[i].perms.allow,
					&pace->e_perm, flags);
		pace->e_id = state->groups->aces[i].uid;
		add_to_mask(state, &state->groups->aces[i].perms);
	}

	pace++;
	pace->e_tag = ACL_MASK;
	low_mode_from_nfs4(state->mask.allow, &pace->e_perm, flags);
	pace->e_id = ACL_UNDEFINED_ID;

	pace++;
	pace->e_tag = ACL_OTHER;
	error = check_deny(state->other.deny, 0);
	if (error)
		goto out_err;
	low_mode_from_nfs4(state->other.allow, &pace->e_perm, flags);
	pace->e_id = ACL_UNDEFINED_ID;

	return pacl;
out_err:
	posix_acl_release(pacl);
	return ERR_PTR(error);
}

static inline void allow_bits(struct posix_ace_state *astate, u32 mask)
{
	/* Allow all bits in the mask not already denied: */
	astate->allow |= mask & ~astate->deny;
}

static inline void deny_bits(struct posix_ace_state *astate, u32 mask)
{
	/* Deny all bits in the mask not already allowed: */
	astate->deny |= mask & ~astate->allow;
}

static int find_uid(struct posix_acl_state *state, struct posix_ace_state_array *a, uid_t uid)
{
	int i;

	for (i = 0; i < a->n; i++)
		if (a->aces[i].uid == uid)
			return i;
	/* Not found: */
	a->n++;
	a->aces[i].uid = uid;
	a->aces[i].perms.allow = state->everyone.allow;
	a->aces[i].perms.deny  = state->everyone.deny;

	return i;
}

static void deny_bits_array(struct posix_ace_state_array *a, u32 mask)
{
	int i;

	for (i=0; i < a->n; i++)
		deny_bits(&a->aces[i].perms, mask);
}

static void allow_bits_array(struct posix_ace_state_array *a, u32 mask)
{
	int i;

	for (i=0; i < a->n; i++)
		allow_bits(&a->aces[i].perms, mask);
}

static void process_one_v4_ace(struct posix_acl_state *state,
				struct nfs4_ace *ace)
{
	u32 mask = ace->access_mask;
	int i;

	state->empty = 0;

	switch (ace2type(ace)) {
	case ACL_USER_OBJ:
		if (ace->type == NFS4_ACE_ACCESS_ALLOWED_ACE_TYPE) {
			allow_bits(&state->owner, mask);
		} else {
			deny_bits(&state->owner, mask);
		}
		break;
	case ACL_USER:
		i = find_uid(state, state->users, ace->who);
		if (ace->type == NFS4_ACE_ACCESS_ALLOWED_ACE_TYPE) {
			allow_bits(&state->users->aces[i].perms, mask);
		} else {
			deny_bits(&state->users->aces[i].perms, mask);
			mask = state->users->aces[i].perms.deny;
			deny_bits(&state->owner, mask);
		}
		break;
	case ACL_GROUP_OBJ:
		if (ace->type == NFS4_ACE_ACCESS_ALLOWED_ACE_TYPE) {
			allow_bits(&state->group, mask);
		} else {
			deny_bits(&state->group, mask);
			mask = state->group.deny;
			deny_bits(&state->owner, mask);
			deny_bits(&state->everyone, mask);
			deny_bits_array(state->users, mask);
			deny_bits_array(state->groups, mask);
		}
		break;
	case ACL_GROUP:
		i = find_uid(state, state->groups, ace->who);
		if (ace->type == NFS4_ACE_ACCESS_ALLOWED_ACE_TYPE) {
			allow_bits(&state->groups->aces[i].perms, mask);
		} else {
			deny_bits(&state->groups->aces[i].perms, mask);
			mask = state->groups->aces[i].perms.deny;
			deny_bits(&state->owner, mask);
			deny_bits(&state->group, mask);
			deny_bits(&state->everyone, mask);
			deny_bits_array(state->users, mask);
			deny_bits_array(state->groups, mask);
		}
		break;
	case ACL_OTHER:
		if (ace->type == NFS4_ACE_ACCESS_ALLOWED_ACE_TYPE) {
			allow_bits(&state->owner, mask);
			allow_bits(&state->group, mask);
			allow_bits(&state->other, mask);
			allow_bits(&state->everyone, mask);
			allow_bits_array(state->users, mask);
			allow_bits_array(state->groups, mask);
		} else {
			deny_bits(&state->owner, mask);
			deny_bits(&state->group, mask);
			deny_bits(&state->other, mask);
			deny_bits(&state->everyone, mask);
			deny_bits_array(state->users, mask);
			deny_bits_array(state->groups, mask);
		}
	}
}

int nfs4_acl_nfsv4_to_posix(struct nfs4_acl *acl, struct posix_acl **pacl,
			    struct posix_acl **dpacl, unsigned int flags)
{
	struct posix_acl_state effective_acl_state, default_acl_state;
	struct nfs4_ace *ace;
	int ret;

	ret = init_state(&effective_acl_state, acl->naces);
	if (ret)
		return ret;
	ret = init_state(&default_acl_state, acl->naces);
	if (ret)
		goto out_estate;
	ret = -EINVAL;
	for (ace = acl->aces; ace < acl->aces + acl->naces; ace++) {
		if (ace->type != NFS4_ACE_ACCESS_ALLOWED_ACE_TYPE &&
		    ace->type != NFS4_ACE_ACCESS_DENIED_ACE_TYPE)
			goto out_dstate;
		if (ace->flag & ~NFS4_SUPPORTED_FLAGS)
			goto out_dstate;
		if ((ace->flag & NFS4_INHERITANCE_FLAGS) == 0) {
			process_one_v4_ace(&effective_acl_state, ace);
			continue;
		}
		if (!(flags & NFS4_ACL_DIR))
			goto out_dstate;
		/*
		 * Note that when only one of FILE_INHERIT or DIRECTORY_INHERIT
		 * is set, we're effectively turning on the other.  That's OK,
		 * according to rfc 3530.
		 */
		process_one_v4_ace(&default_acl_state, ace);

		if (!(ace->flag & NFS4_ACE_INHERIT_ONLY_ACE))
			process_one_v4_ace(&effective_acl_state, ace);
	}
	*pacl = posix_state_to_acl(&effective_acl_state, flags);
	if (IS_ERR(*pacl)) {
		ret = PTR_ERR(*pacl);
		*pacl = NULL;
		goto out_dstate;
	}
	*dpacl = posix_state_to_acl(&default_acl_state,
						flags | NFS4_ACL_TYPE_DEFAULT);
	if (IS_ERR(*dpacl)) {
		ret = PTR_ERR(*dpacl);
		*dpacl = NULL;
		posix_acl_release(*pacl);
		*pacl = NULL;
		goto out_dstate;
	}
	sort_pacl(*pacl);
	sort_pacl(*dpacl);
	ret = 0;
out_dstate:
	free_state(&default_acl_state);
out_estate:
	free_state(&effective_acl_state);
	return ret;
}

static short
ace2type(struct nfs4_ace *ace)
{
	switch (ace->whotype) {
		case NFS4_ACL_WHO_NAMED:
			return (ace->flag & NFS4_ACE_IDENTIFIER_GROUP ?
					ACL_GROUP : ACL_USER);
		case NFS4_ACL_WHO_OWNER:
			return ACL_USER_OBJ;
		case NFS4_ACL_WHO_GROUP:
			return ACL_GROUP_OBJ;
		case NFS4_ACL_WHO_EVERYONE:
			return ACL_OTHER;
	}
	BUG();
	return -1;
}

EXPORT_SYMBOL(nfs4_acl_posix_to_nfsv4);
EXPORT_SYMBOL(nfs4_acl_nfsv4_to_posix);

struct nfs4_acl *
nfs4_acl_new(int n)
{
	struct nfs4_acl *acl;

	acl = kmalloc(sizeof(*acl) + n*sizeof(struct nfs4_ace), GFP_KERNEL);
	if (acl == NULL)
		return NULL;
	acl->naces = 0;
	return acl;
}

static struct {
	char *string;
	int   stringlen;
	int type;
} s2t_map[] = {
	{
		.string    = "OWNER@",
		.stringlen = sizeof("OWNER@") - 1,
		.type      = NFS4_ACL_WHO_OWNER,
	},
	{
		.string    = "GROUP@",
		.stringlen = sizeof("GROUP@") - 1,
		.type      = NFS4_ACL_WHO_GROUP,
	},
	{
		.string    = "EVERYONE@",
		.stringlen = sizeof("EVERYONE@") - 1,
		.type      = NFS4_ACL_WHO_EVERYONE,
	},
};

int
nfs4_acl_get_whotype(char *p, u32 len)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(s2t_map); i++) {
		if (s2t_map[i].stringlen == len &&
				0 == memcmp(s2t_map[i].string, p, len))
			return s2t_map[i].type;
	}
	return NFS4_ACL_WHO_NAMED;
}

int
nfs4_acl_write_who(int who, char *p)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(s2t_map); i++) {
		if (s2t_map[i].type == who) {
			memcpy(p, s2t_map[i].string, s2t_map[i].stringlen);
			return s2t_map[i].stringlen;
		}
	}
	BUG();
	return -1;
}

EXPORT_SYMBOL(nfs4_acl_new);
EXPORT_SYMBOL(nfs4_acl_get_whotype);
EXPORT_SYMBOL(nfs4_acl_write_who);