Re: [libnftnl PATCH v2] ruleset: fix crash if we free sets included in the set_list

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Tue, Feb 17, 2015 at 03:03:51PM +0100, Alvaro Neira Ayuso wrote:
> When we parse a ruleset which has a rule using a set. First step is parse the
> set, set up an id and add it to a set list. Later, we use this set list to find
> the set associated to the rule and we set up the set id to the expression
> (lookup expression) of the rule.
> 
> The problem is if we return this set using the function
> nft_ruleset_parse_file_cb and we free this set. We have a crash when we try to
> iterate in the set list.
> 
> This patch solves it, cloning the set and adding the new set to the set list.
> 
> Signed-off-by: Alvaro Neira Ayuso <alvaroneay@gmail.com>
> ---
> [changes in v2]
>  * Added the function to clone set and set elems.
> 
>  include/libnftnl/set.h |    2 ++
>  src/ruleset.c          |    8 +++++++-
>  src/set.c              |   52 ++++++++++++++++++++++++++++++++++++++++++++++++
>  src/set_elem.c         |   27 +++++++++++++++++++++++++
>  4 files changed, 88 insertions(+), 1 deletion(-)
> 
> diff --git a/include/libnftnl/set.h b/include/libnftnl/set.h
> index 7f3504f..3f8ef87 100644
> --- a/include/libnftnl/set.h
> +++ b/include/libnftnl/set.h
> @@ -42,6 +42,7 @@ const void *nft_set_attr_get_data(struct nft_set *s, uint16_t attr,
>  				  uint32_t *data_len);
>  const char *nft_set_attr_get_str(struct nft_set *s, uint16_t attr);
>  uint32_t nft_set_attr_get_u32(struct nft_set *s, uint16_t attr);
> +struct nft_set *nft_set_clone(const struct nft_set *set);
>  
>  struct nlmsghdr;
>  
> @@ -103,6 +104,7 @@ const char *nft_set_elem_attr_get_str(struct nft_set_elem *s, uint16_t attr);
>  uint32_t nft_set_elem_attr_get_u32(struct nft_set_elem *s, uint16_t attr);
>  
>  bool nft_set_elem_attr_is_set(const struct nft_set_elem *s, uint16_t attr);
> +struct nft_set_elem *nft_set_elem_clone(struct nft_set_elem *elem);
>  
>  #define nft_set_elem_nlmsg_build_hdr	nft_nlmsg_build_hdr
>  void nft_set_elems_nlmsg_build_payload(struct nlmsghdr *nlh, struct nft_set *s);
> diff --git a/src/ruleset.c b/src/ruleset.c
> index 89ea344..bc669c0 100644
> --- a/src/ruleset.c
> +++ b/src/ruleset.c
> @@ -312,8 +312,14 @@ static int nft_ruleset_parse_set(struct nft_parse_ctx *ctx,
>  				 struct nft_set *set, uint32_t type,
>  				 struct nft_parse_err *err)
>  {
> +	struct nft_set *newset;
> +
>  	nft_set_attr_set_u32(set, NFT_SET_ATTR_ID, ctx->set_id++);
> -	nft_set_list_add_tail(set, ctx->set_list);
> +	newset = nft_set_clone(set);
> +	if (newset == NULL)
> +		goto err;
> +
> +	nft_set_list_add_tail(newset, ctx->set_list);
>  
>  	nft_ruleset_ctx_set_u32(ctx, NFT_RULESET_CTX_TYPE, type);
>  	nft_ruleset_ctx_set(ctx, NFT_RULESET_CTX_SET, set);
> diff --git a/src/set.c b/src/set.c
> index c6c3301..5fd5245 100644
> --- a/src/set.c
> +++ b/src/set.c
> @@ -249,6 +249,58 @@ uint32_t nft_set_attr_get_u32(struct nft_set *s, uint16_t attr)
>  }
>  EXPORT_SYMBOL(nft_set_attr_get_u32);
>  
> +struct nft_set *nft_set_clone(const struct nft_set *set)
> +{
> +	struct nft_set *newset;
> +	struct nft_set_elem *elem, *tmp, *newelem;
> +
> +	newset = nft_set_alloc();
> +	if (newset == NULL)
> +		return NULL;
> +

You better memcmpy() to save these many LOCs...

> +	if (set->flags & (1 << NFT_SET_ATTR_TABLE))
> +		nft_set_attr_set_str(newset, NFT_SET_ATTR_TABLE, set->table);
> +	if (set->flags & (1 << NFT_SET_ATTR_NAME))
> +		nft_set_attr_set_str(newset, NFT_SET_ATTR_NAME, set->name);
> +	if (set->flags & (1 << NFT_SET_ATTR_FLAGS))
> +		nft_set_attr_set_u32(newset, NFT_SET_ATTR_FLAGS,
> +				     set->set_flags);
> +	if (set->flags & (1 << NFT_SET_ATTR_KEY_TYPE))
> +		nft_set_attr_set_u32(newset, NFT_SET_ATTR_KEY_TYPE,
> +				     set->key_type);
> +	if (set->flags & (1 << NFT_SET_ATTR_KEY_LEN))
> +		nft_set_attr_set_u32(newset, NFT_SET_ATTR_KEY_LEN,
> +				     set->key_len);
> +	if (set->flags & (1 << NFT_SET_ATTR_DATA_TYPE))
> +		nft_set_attr_set_u32(newset, NFT_SET_ATTR_DATA_TYPE,
> +				     set->data_type);
> +	if (set->flags & (1 << NFT_SET_ATTR_DATA_LEN))
> +		nft_set_attr_set_u32(newset, NFT_SET_ATTR_DATA_LEN,
> +				     set->data_len);
> +	if (set->flags & (1 << NFT_SET_ATTR_FAMILY))
> +		nft_set_attr_set_u32(newset, NFT_SET_ATTR_FAMILY, set->family);
> +	if (set->flags & (1 << NFT_SET_ATTR_ID))
> +		nft_set_attr_set_u32(newset, NFT_SET_ATTR_ID, set->id);
> +	if (set->flags & (1 << NFT_SET_ATTR_POLICY))
> +		nft_set_attr_set_u32(newset, NFT_SET_ATTR_POLICY, set->policy);
> +	if (set->flags & (1 << NFT_SET_ATTR_DESC_SIZE))
> +		nft_set_attr_set_u32(newset, NFT_SET_ATTR_DESC_SIZE,
> +				     set->desc.size);