netdev - Re: [PATCHv2 net] sctp: get sctphdr by offset in sctp_compute

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Message-ID: <20190319111205.GA3722@hmswarspite.think-freely.org>
Date:   Tue, 19 Mar 2019 07:12:05 -0400
From:   Neil Horman <nhorman@...driver.com>
To:     Xin Long <lucien.xin@...il.com>
Cc:     network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org,
        davem@...emloft.net, Florian Westphal <fw@...len.de>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Subject: Re: [PATCHv2 net] sctp: get sctphdr by offset in sctp_compute_cksum

On Mon, Mar 18, 2019 at 07:47:00PM +0800, Xin Long wrote:
> sctp_hdr(skb) only works when skb->transport_header is set properly.
> 
> But in Netfilter, skb->transport_header for ipv6 is not guaranteed
> to be right value for sctphdr. It would cause to fail to check the
> checksum for sctp packets.
> 
> So fix it by using offset, which is always right in all places.
> 
> v1->v2:
>   - Fix the changelog.
> 
> Fixes: e6d8b64b34aa ("net: sctp: fix and consolidate SCTP checksumming code")
> Reported-by: Li Shuang <shuali@...hat.com>
> Signed-off-by: Xin Long <lucien.xin@...il.com>
> ---
>  include/net/sctp/checksum.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/net/sctp/checksum.h b/include/net/sctp/checksum.h
> index 32ee65a..1c6e6c0 100644
> --- a/include/net/sctp/checksum.h
> +++ b/include/net/sctp/checksum.h
> @@ -61,7 +61,7 @@ static inline __wsum sctp_csum_combine(__wsum csum, __wsum csum2,
>  static inline __le32 sctp_compute_cksum(const struct sk_buff *skb,
>  					unsigned int offset)
>  {
> -	struct sctphdr *sh = sctp_hdr(skb);
> +	struct sctphdr *sh = (struct sctphdr *)(skb->data + offset);
>  	const struct skb_checksum_ops ops = {
>  		.update  = sctp_csum_update,
>  		.combine = sctp_csum_combine,
> -- 
> 2.1.0
> 
> 
Acked-by: Neil Horman <nhorman@...driver.com>