[PATCH nf] netfilter: nf_tables: free flowtable hooks on hook register error

[PATCH nf] netfilter: nf_tables: free flowtable hooks on hook register error

[Florian Westphal]

If hook registration fails, the hooks allocated via nft_netdev_hook_alloc
need to be freed.

We can't change the goto label to 'goto 5' -- while it does fix the memleak
it does cause a warning splat from the netfilter core (the hooks were not
registered).

Fixes: 3f0465a9ef02 ("netfilter: nf_tables: dynamically allocate hooks per net_device in flowtables")
Reported-by: syzbot+a2ff6fa45162a5ed4dd3@syzkaller.appspotmail.com
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nf_tables_api.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index d1318bdf49ca..bb064aa4154b 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -6300,8 +6300,13 @@ static int nf_tables_newflowtable(struct net *net, struct sock *nlsk,
 		goto err4;
 
 	err = nft_register_flowtable_net_hooks(ctx.net, table, flowtable);
-	if (err < 0)
+	if (err < 0) {
+		list_for_each_entry_safe(hook, next, &flowtable->hook_list, list) {
+			list_del_rcu(&hook->list);
+			kfree_rcu(hook, rcu);
+		}
 		goto err4;
+	}
 
 	err = nft_trans_flowtable_add(&ctx, NFT_MSG_NEWFLOWTABLE, flowtable);
 	if (err < 0)
-- 
2.24.1

Re: [PATCH nf] netfilter: nf_tables: free flowtable hooks on hook register error

[Pablo Neira Ayuso]

On Mon, Mar 02, 2020 at 09:58:50PM +0100, Florian Westphal wrote:
> If hook registration fails, the hooks allocated via nft_netdev_hook_alloc
> need to be freed.
> 
> We can't change the goto label to 'goto 5' -- while it does fix the memleak
> it does cause a warning splat from the netfilter core (the hooks were not
> registered).

Applied, thanks.

Re: [PATCH nf] netfilter: nf_tables: free flowtable hooks on hook register error

[Pablo Neira Ayuso]

On Mon, Mar 02, 2020 at 09:58:50PM +0100, Florian Westphal wrote:
> If hook registration fails, the hooks allocated via nft_netdev_hook_alloc
> need to be freed.
> 
> We can't change the goto label to 'goto 5' -- while it does fix the memleak
> it does cause a warning splat from the netfilter core (the hooks were not
> registered).

It seems test/shell crashes after this, looking. It works after
reverting.

> Fixes: 3f0465a9ef02 ("netfilter: nf_tables: dynamically allocate hooks per net_device in flowtables")
> Reported-by: syzbot+a2ff6fa45162a5ed4dd3@syzkaller.appspotmail.com
> Signed-off-by: Florian Westphal <fw@strlen.de>
> ---
>  net/netfilter/nf_tables_api.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
> index d1318bdf49ca..bb064aa4154b 100644
> --- a/net/netfilter/nf_tables_api.c
> +++ b/net/netfilter/nf_tables_api.c
> @@ -6300,8 +6300,13 @@ static int nf_tables_newflowtable(struct net *net, struct sock *nlsk,
>  		goto err4;
>  
>  	err = nft_register_flowtable_net_hooks(ctx.net, table, flowtable);
> -	if (err < 0)
> +	if (err < 0) {
> +		list_for_each_entry_safe(hook, next, &flowtable->hook_list, list) {
> +			list_del_rcu(&hook->list);
> +			kfree_rcu(hook, rcu);
> +		}
>  		goto err4;
> +	}
>  
>  	err = nft_trans_flowtable_add(&ctx, NFT_MSG_NEWFLOWTABLE, flowtable);
>  	if (err < 0)
> -- 
> 2.24.1
> 

Re: [PATCH nf] netfilter: nf_tables: free flowtable hooks on hook register error

[Florian Westphal]

Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> On Mon, Mar 02, 2020 at 09:58:50PM +0100, Florian Westphal wrote:
> > If hook registration fails, the hooks allocated via nft_netdev_hook_alloc
> > need to be freed.
> > 
> > We can't change the goto label to 'goto 5' -- while it does fix the memleak
> > it does cause a warning splat from the netfilter core (the hooks were not
> > registered).
> 
> It seems test/shell crashes after this, looking. It works after
> reverting.

Sorry about that.  Let me know if you want me to look into this.

Re: [PATCH nf] netfilter: nf_tables: free flowtable hooks on hook register error

[Pablo Neira Ayuso]

On Thu, Mar 05, 2020 at 01:10:12PM +0100, Pablo Neira Ayuso wrote:
> On Mon, Mar 02, 2020 at 09:58:50PM +0100, Florian Westphal wrote:
> > If hook registration fails, the hooks allocated via nft_netdev_hook_alloc
> > need to be freed.
> > 
> > We can't change the goto label to 'goto 5' -- while it does fix the memleak
> > it does cause a warning splat from the netfilter core (the hooks were not
> > registered).
> 
> It seems test/shell crashes after this, looking. It works after
> reverting.

Actually, no problem problem is not related to this patch. Sorry for
the noise.