Re: [PATCH nft 2/2] netfilter: nf_tables: Fix potential data-race in __nft_obj_type_get()

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

On Sun, Apr 07, 2024 at 02:56:05PM +0800, Ziyang Xuan wrote:
> nft_unregister_obj() can concurrent with __nft_obj_type_get(),
> and there is not any protection when iterate over nf_tables_objects
> list in __nft_obj_type_get(). Therefore, there is pertential
> data-race of nf_tables_objects list entry.
> 
> Use list_for_each_entry_rcu() to iterate over nf_tables_objects
> list in __nft_obj_type_get(), and use rcu_read_lock() in the caller
> nft_obj_type_get() to protect the entire type query process.

Also applied, thanks

> Fixes: e50092404c1b ("netfilter: nf_tables: add stateful objects")
> Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
> ---
>  net/netfilter/nf_tables_api.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> index 646d59685cfd..70fe0ca24d34 100644
> --- a/net/netfilter/nf_tables_api.c
> +++ b/net/netfilter/nf_tables_api.c
> @@ -7607,7 +7607,7 @@ static const struct nft_object_type *__nft_obj_type_get(u32 objtype, u8 family)
>  {
>  	const struct nft_object_type *type;
>  
> -	list_for_each_entry(type, &nf_tables_objects, list) {
> +	list_for_each_entry_rcu(type, &nf_tables_objects, list) {
>  		if (type->family != NFPROTO_UNSPEC &&
>  		    type->family != family)
>  			continue;
> @@ -7623,9 +7623,13 @@ nft_obj_type_get(struct net *net, u32 objtype, u8 family)
>  {
>  	const struct nft_object_type *type;
>  
> +	rcu_read_lock();
>  	type = __nft_obj_type_get(objtype, family);
> -	if (type != NULL && try_module_get(type->owner))
> +	if (type != NULL && try_module_get(type->owner)) {
> +		rcu_read_unlock();
>  		return type;
> +	}
> +	rcu_read_unlock();
>  
>  	lockdep_nfnl_nft_mutex_not_held();
>  #ifdef CONFIG_MODULES
> -- 
> 2.25.1
>