linux-kernel - Re: [PATCH v3,net-next 2/2] ip6_gre: fix potential memory leak in ip6erspan

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Message-ID: <CALDO+SYAFmHzqEu3E6xXRm0DdECVkvf_5dKCz-_A8Nrc0fbuMw@mail.gmail.com>
Date:   Wed, 20 Dec 2017 06:11:27 -0800
From:   William Tu <u9012063@...il.com>
To:     Haishuang Yan <yanhaishuang@...s.chinamobile.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3,net-next 2/2] ip6_gre: fix potential memory leak in ip6erspan_rcv

On Tue, Dec 19, 2017 at 6:07 PM, Haishuang Yan
<yanhaishuang@...s.chinamobile.com> wrote:
> If md is NULL, tun_dst must be freed, otherwise it will cause memory
> leak.
>
> Fixes: ef7baf5e083c ("ip6_gre: add ip6 erspan collect_md mode")
> Cc: William Tu <u9012063@...il.com>
> Signed-off-by: Haishuang Yan <yanhaishuang@...s.chinamobile.com>
>
> ---
> Changes since v3:
>   * Rebase on latest master branch.
>   * Fix wrong commit information.
> ---
>  net/ipv6/ip6_gre.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
> index 9bd1103..45038a9 100644
> --- a/net/ipv6/ip6_gre.c
> +++ b/net/ipv6/ip6_gre.c
> @@ -550,8 +550,10 @@ static int ip6erspan_rcv(struct sk_buff *skb, int gre_hdr_len,
>
>                         info = &tun_dst->u.tun_info;
>                         md = ip_tunnel_info_opts(info);
> -                       if (!md)
> +                       if (!md) {
> +                               dst_release((struct dst_entry *)tun_dst);
>                                 return PACKET_REJECT;
isn't md allocated previously at
    tun_dst = ipv6_tun_rx_dst(skb, flags, tun_id,
                                           sizeof(*md));
so md should never be null after we check tun_dst?
William