netdev - Re: [PATCH net] udplite: fix partial checksum initialization

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Message-Id: <20180216.155826.1914997978700216998.davem@davemloft.net>
Date:   Fri, 16 Feb 2018 15:58:26 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     alexey.kodanev@...cle.com
Cc:     netdev@...r.kernel.org, tom@...bertland.com
Subject: Re: [PATCH net] udplite: fix partial checksum initialization

From: Alexey Kodanev <alexey.kodanev@...cle.com>
Date: Thu, 15 Feb 2018 20:18:43 +0300

> Since UDP-Lite is always using checksum, the following path is
> triggered when calculating pseudo header for it:
> 
>   udp4_csum_init() or udp6_csum_init()
>     skb_checksum_init_zero_check()
>       __skb_checksum_validate_complete()
> 
> The problem can appear if skb->len is less than CHECKSUM_BREAK. In
> this particular case __skb_checksum_validate_complete() also invokes
> __skb_checksum_complete(skb). If UDP-Lite is using partial checksum
> that covers only part of a packet, the function will return bad
> checksum and the packet will be dropped.
> 
> It can be fixed if we skip skb_checksum_init_zero_check() and only
> set the required pseudo header checksum for UDP-Lite with partial
> checksum before udp4_csum_init()/udp6_csum_init() functions return.
> 
> Fixes: ed70fcfcee95 ("net: Call skb_checksum_init in IPv4")
> Fixes: e4f45b7f40bd ("net: Call skb_checksum_init in IPv6")
> Signed-off-by: Alexey Kodanev <alexey.kodanev@...cle.com>

Applied and queued up for -stable, thanks Alexey.