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SubjectRe: [PATCH 4.4 38/97] netfilter: xt_CT: fix refcnt leak on error path
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On Fri, 2018-03-23 at 10:54 +0100, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me know.
>
> ------------------
>
> From: Gao Feng <fgao@ikuai8.com>
>
>
> [ Upstream commit 470acf55a021713869b9bcc967268ac90c8a0fac ]
[...]
> --- a/net/netfilter/xt_CT.c
> +++ b/net/netfilter/xt_CT.c
> @@ -168,8 +168,10 @@ xt_ct_set_timeout(struct nf_conn *ct, co
>   goto err_put_timeout;
>   }
>   timeout_ext = nf_ct_timeout_ext_add(ct, timeout, GFP_ATOMIC);
> - if (timeout_ext == NULL)
> + if (!timeout_ext) {
>   ret = -ENOMEM;
> + goto err_put_timeout;
> + }
>  
>   rcu_read_unlock();
>   return ret;

This part looks fine.

> @@ -201,6 +203,7 @@ static int xt_ct_tg_check(const struct x
> >     struct xt_ct_target_info_v1 *info)
>  {
>   struct nf_conntrack_zone zone;
> + struct nf_conn_help *help;
>   struct nf_conn *ct;
>   int ret = -EOPNOTSUPP;
>  
> @@ -249,7 +252,7 @@ static int xt_ct_tg_check(const struct x
>   if (info->timeout[0]) {
>   ret = xt_ct_set_timeout(ct, par, info->timeout);
>   if (ret < 0)
> - goto err3;
> + goto err4;
>   }
>   __set_bit(IPS_CONFIRMED_BIT, &ct->status);
>   nf_conntrack_get(&ct->ct_general);
> @@ -257,6 +260,10 @@ out:
>   info->ct = ct;
>   return 0;
>  
> +err4:
> + help = nfct_help(ct);
> + if (help)
> + module_put(help->helper->me);
>  err3:
>   nf_ct_tmpl_free(ct);
>  err2:

This does not. nf_ct_tmpl_free() calls nf_ct_ext_destroy() which I
think will call back into xt_ct_tg_destroy(). So I think the module
reference is already dropped here and we mustn't do it twice. Am I
missing something?

Ben.

--
Ben Hutchings
Software Developer, Codethink Ltd.

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