netdev - Re: [PATCH net] udp: fix a skb extensions leak

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Message-ID: <CADvbK_fOKPMeVynjxBOZc3tRFEcp9xYpyC9j0Hbs9E1sa6R5LQ@mail.gmail.com>
Date:   Thu, 26 Mar 2020 17:28:44 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     network dev <netdev@...r.kernel.org>
Cc:     davem <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>,
        Steffen Klassert <steffen.klassert@...unet.com>
Subject: Re: [PATCH net] udp: fix a skb extensions leak

CC Steffen Klassert <steffen.klassert@...unet.com>

On Thu, Mar 26, 2020 at 5:06 PM Xin Long <lucien.xin@...il.com> wrote:
>
> On udp rx path udp_rcv_segment() may do segment where the frag skbs
> will get the header copied from the head skb in skb_segment_list()
> by calling __copy_skb_header(), which could overwrite the frag skbs'
> extensions by __skb_ext_copy() and cause a leak.
>
> This issue was found after loading esp_offload where a sec path ext
> is set in the skb.
>
> On udp tx gso path, it works well as the frag skbs' extensions are
> not set. So this issue should be fixed on udp's rx path only and
> release the frag skbs' extensions before going to do segment.
>
> Reported-by: Xiumei Mu <xmu@...hat.com>
> Fixes: cf329aa42b66 ("udp: cope with UDP GRO packet misdirection")
> Signed-off-by: Xin Long <lucien.xin@...il.com>
> ---
>  include/net/udp.h | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/include/net/udp.h b/include/net/udp.h
> index e55d5f7..7bf0ca5 100644
> --- a/include/net/udp.h
> +++ b/include/net/udp.h
> @@ -486,6 +486,10 @@ static inline struct sk_buff *udp_rcv_segment(struct sock *sk,
>         if (skb->pkt_type == PACKET_LOOPBACK)
>                 skb->ip_summed = CHECKSUM_PARTIAL;
>
> +       if (skb_has_frag_list(skb) && skb_has_extensions(skb))
> +               skb_walk_frags(skb, segs)
> +                       skb_ext_put(segs);
> +
>         /* the GSO CB lays after the UDP one, no need to save and restore any
>          * CB fragment
>          */
> --
> 2.1.0
>