Re: [PATCH 4/6] selinux: convert cond_av_list to array

[Stephen Smalley <sds@tycho.nsa.gov>]

On 1/16/20 7:04 AM, Ondrej Mosnacek wrote:
> Since it is fixed-size after allocation and we know the size beforehand,
> using a plain old array is simpler and more efficient.
> 
> Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>

Reviewed-by: Stephen Smalley <sds@tycho.nsa.gov>

> ---
>   security/selinux/ss/conditional.c | 125 ++++++++++++------------------
>   security/selinux/ss/conditional.h |   8 +-
>   2 files changed, 53 insertions(+), 80 deletions(-)
> 
> diff --git a/security/selinux/ss/conditional.c b/security/selinux/ss/conditional.c
> index c8a02c9b23ee..b847fd2a6a51 100644
> --- a/security/selinux/ss/conditional.c
> +++ b/security/selinux/ss/conditional.c
> @@ -87,8 +87,9 @@ static int cond_evaluate_expr(struct policydb *p, struct cond_expr *expr)
>    */
>   void evaluate_cond_node(struct policydb *p, struct cond_node *node)
>   {
> +	struct avtab_node *avnode;
>   	int new_state;
> -	struct cond_av_list *cur;
> +	u32 i;
>   
>   	new_state = cond_evaluate_expr(p, node->expr);
>   	if (new_state != node->cur_state) {
> @@ -96,19 +97,21 @@ void evaluate_cond_node(struct policydb *p, struct cond_node *node)
>   		if (new_state == -1)
>   			pr_err("SELinux: expression result was undefined - disabling all rules.\n");
>   		/* turn the rules on or off */
> -		for (cur = node->true_list; cur; cur = cur->next) {
> +		for (i = 0; i < node->true_list.len; i++) {
> +			avnode = node->true_list.nodes[i];
>   			if (new_state <= 0)
> -				cur->node->key.specified &= ~AVTAB_ENABLED;
> +				avnode->key.specified &= ~AVTAB_ENABLED;
>   			else
> -				cur->node->key.specified |= AVTAB_ENABLED;
> +				avnode->key.specified |= AVTAB_ENABLED;
>   		}
>   
> -		for (cur = node->false_list; cur; cur = cur->next) {
> +		for (i = 0; i < node->false_list.len; i++) {
> +			avnode = node->false_list.nodes[i];
>   			/* -1 or 1 */
>   			if (new_state)
> -				cur->node->key.specified &= ~AVTAB_ENABLED;
> +				avnode->key.specified &= ~AVTAB_ENABLED;
>   			else
> -				cur->node->key.specified |= AVTAB_ENABLED;
> +				avnode->key.specified |= AVTAB_ENABLED;
>   		}
>   	}
>   }
> @@ -128,16 +131,6 @@ int cond_policydb_init(struct policydb *p)
>   	return 0;
>   }
>   
> -static void cond_av_list_destroy(struct cond_av_list *list)
> -{
> -	struct cond_av_list *cur, *next;
> -	for (cur = list; cur; cur = next) {
> -		next = cur->next;
> -		/* the avtab_ptr_t node is destroy by the avtab */
> -		kfree(cur);
> -	}
> -}
> -
>   static void cond_node_destroy(struct cond_node *node)
>   {
>   	struct cond_expr *cur_expr, *next_expr;
> @@ -146,8 +139,9 @@ static void cond_node_destroy(struct cond_node *node)
>   		next_expr = cur_expr->next;
>   		kfree(cur_expr);
>   	}
> -	cond_av_list_destroy(node->true_list);
> -	cond_av_list_destroy(node->false_list);
> +	/* the avtab_ptr_t nodes are destroyed by the avtab */
> +	kfree(node->true_list.nodes);
> +	kfree(node->false_list.nodes);
>   }
>   
>   static void cond_list_destroy(struct policydb *p)
> @@ -255,19 +249,17 @@ err:
>   
>   struct cond_insertf_data {
>   	struct policydb *p;
> +	struct avtab_node **dst;
>   	struct cond_av_list *other;
> -	struct cond_av_list *head;
> -	struct cond_av_list *tail;
>   };
>   
>   static int cond_insertf(struct avtab *a, struct avtab_key *k, struct avtab_datum *d, void *ptr)
>   {
>   	struct cond_insertf_data *data = ptr;
>   	struct policydb *p = data->p;
> -	struct cond_av_list *other = data->other, *list, *cur;
>   	struct avtab_node *node_ptr;
> -	u8 found;
> -	int rc = -EINVAL;
> +	u32 i;
> +	bool found;
>   
>   	/*
>   	 * For type rules we have to make certain there aren't any
> @@ -277,7 +269,7 @@ static int cond_insertf(struct avtab *a, struct avtab_key *k, struct avtab_datum
>   	if (k->specified & AVTAB_TYPE) {
>   		if (avtab_search(&p->te_avtab, k)) {
>   			pr_err("SELinux: type rule already exists outside of a conditional.\n");
> -			goto err;
> +			return -EINVAL;
>   		}
>   		/*
>   		 * If we are reading the false list other will be a pointer to
> @@ -287,29 +279,29 @@ static int cond_insertf(struct avtab *a, struct avtab_key *k, struct avtab_datum
>   		 * If we are reading the true list (other == NULL) there shouldn't
>   		 * be any other entries.
>   		 */
> -		if (other) {
> +		if (data->other) {
>   			node_ptr = avtab_search_node(&p->te_cond_avtab, k);
>   			if (node_ptr) {
>   				if (avtab_search_node_next(node_ptr, k->specified)) {
>   					pr_err("SELinux: too many conflicting type rules.\n");
> -					goto err;
> +					return -EINVAL;
>   				}
> -				found = 0;
> -				for (cur = other; cur; cur = cur->next) {
> -					if (cur->node == node_ptr) {
> -						found = 1;
> +				found = false;
> +				for (i = 0; i < data->other->len; i++) {
> +					if (data->other->nodes[i] == node_ptr) {
> +						found = true;
>   						break;
>   					}
>   				}
>   				if (!found) {
>   					pr_err("SELinux: conflicting type rules.\n");
> -					goto err;
> +					return -EINVAL;
>   				}
>   			}
>   		} else {
>   			if (avtab_search(&p->te_cond_avtab, k)) {
>   				pr_err("SELinux: conflicting type rules when adding type rule for true.\n");
> -				goto err;
> +				return -EINVAL;
>   			}
>   		}
>   	}
> @@ -317,39 +309,22 @@ static int cond_insertf(struct avtab *a, struct avtab_key *k, struct avtab_datum
>   	node_ptr = avtab_insert_nonunique(&p->te_cond_avtab, k, d);
>   	if (!node_ptr) {
>   		pr_err("SELinux: could not insert rule.\n");
> -		rc = -ENOMEM;
> -		goto err;
> -	}
> -
> -	list = kzalloc(sizeof(*list), GFP_KERNEL);
> -	if (!list) {
> -		rc = -ENOMEM;
> -		goto err;
> +		return -ENOMEM;
>   	}
>   
> -	list->node = node_ptr;
> -	if (!data->head)
> -		data->head = list;
> -	else
> -		data->tail->next = list;
> -	data->tail = list;
> +	*data->dst = node_ptr;
>   	return 0;
> -
> -err:
> -	cond_av_list_destroy(data->head);
> -	data->head = NULL;
> -	return rc;
>   }
>   
> -static int cond_read_av_list(struct policydb *p, void *fp, struct cond_av_list **ret_list, struct cond_av_list *other)
> +static int cond_read_av_list(struct policydb *p, void *fp,
> +			     struct cond_av_list *list,
> +			     struct cond_av_list *other)
>   {
> -	int i, rc;
> +	int rc;
>   	__le32 buf[1];
> -	u32 len;
> +	u32 i, len;
>   	struct cond_insertf_data data;
>   
> -	*ret_list = NULL;
> -
>   	rc = next_entry(buf, fp, sizeof(u32));
>   	if (rc)
>   		return rc;
> @@ -358,18 +333,24 @@ static int cond_read_av_list(struct policydb *p, void *fp, struct cond_av_list *
>   	if (len == 0)
>   		return 0;
>   
> +	list->nodes = kcalloc(len, sizeof(*list->nodes), GFP_KERNEL);
> +	if (!list->nodes)
> +		return -ENOMEM;
> +
>   	data.p = p;
>   	data.other = other;
> -	data.head = NULL;
> -	data.tail = NULL;
>   	for (i = 0; i < len; i++) {
> +		data.dst = &list->nodes[i];
>   		rc = avtab_read_item(&p->te_cond_avtab, fp, p, cond_insertf,
>   				     &data);
> -		if (rc)
> +		if (rc) {
> +			kfree(list->nodes);
> +			list->nodes = NULL;
>   			return rc;
> +		}
>   	}
>   
> -	*ret_list = data.head;
> +	list->len = len;
>   	return 0;
>   }
>   
> @@ -432,7 +413,7 @@ static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
>   	rc = cond_read_av_list(p, fp, &node->true_list, NULL);
>   	if (rc)
>   		goto err;
> -	rc = cond_read_av_list(p, fp, &node->false_list, node->true_list);
> +	rc = cond_read_av_list(p, fp, &node->false_list, &node->true_list);
>   	if (rc)
>   		goto err;
>   	return 0;
> @@ -511,24 +492,16 @@ static int cond_write_av_list(struct policydb *p,
>   			      struct cond_av_list *list, struct policy_file *fp)
>   {
>   	__le32 buf[1];
> -	struct cond_av_list *cur_list;
> -	u32 len;
> +	u32 i;
>   	int rc;
>   
> -	len = 0;
> -	for (cur_list = list; cur_list != NULL; cur_list = cur_list->next)
> -		len++;
> -
> -	buf[0] = cpu_to_le32(len);
> +	buf[0] = cpu_to_le32(list->len);
>   	rc = put_entry(buf, sizeof(u32), 1, fp);
>   	if (rc)
>   		return rc;
>   
> -	if (len == 0)
> -		return 0;
> -
> -	for (cur_list = list; cur_list != NULL; cur_list = cur_list->next) {
> -		rc = avtab_write_item(p, cur_list->node, fp);
> +	for (i = 0; i < list->len; i++) {
> +		rc = avtab_write_item(p, list->nodes[i], fp);
>   		if (rc)
>   			return rc;
>   	}
> @@ -565,10 +538,10 @@ static int cond_write_node(struct policydb *p, struct cond_node *node,
>   			return rc;
>   	}
>   
> -	rc = cond_write_av_list(p, node->true_list, fp);
> +	rc = cond_write_av_list(p, &node->true_list, fp);
>   	if (rc)
>   		return rc;
> -	rc = cond_write_av_list(p, node->false_list, fp);
> +	rc = cond_write_av_list(p, &node->false_list, fp);
>   	if (rc)
>   		return rc;
>   
> diff --git a/security/selinux/ss/conditional.h b/security/selinux/ss/conditional.h
> index e474bdd3a0ed..5f97f678440e 100644
> --- a/security/selinux/ss/conditional.h
> +++ b/security/selinux/ss/conditional.h
> @@ -39,8 +39,8 @@ struct cond_expr {
>    * struct is for that list.
>    */
>   struct cond_av_list {
> -	struct avtab_node *node;
> -	struct cond_av_list *next;
> +	struct avtab_node **nodes;
> +	u32 len;
>   };
>   
>   /*
> @@ -53,8 +53,8 @@ struct cond_av_list {
>   struct cond_node {
>   	int cur_state;
>   	struct cond_expr *expr;
> -	struct cond_av_list *true_list;
> -	struct cond_av_list *false_list;
> +	struct cond_av_list true_list;
> +	struct cond_av_list false_list;
>   };
>   
>   int cond_policydb_init(struct policydb *p);
>