netdev - Re: [PATCH net] udp: fix data-race in udp_set_dev

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Message-Id: <20191028.135456.145825661160523017.davem@davemloft.net>
Date:   Mon, 28 Oct 2019 13:54:56 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        syzkaller@...glegroups.com, pabeni@...hat.com
Subject: Re: [PATCH net] udp: fix data-race in udp_set_dev_scratch()

From: Eric Dumazet <edumazet@...gle.com>
Date: Thu, 24 Oct 2019 11:43:31 -0700

> KCSAN reported a data-race in udp_set_dev_scratch() [1]
> 
> The issue here is that we must not write over skb fields
> if skb is shared. A similar issue has been fixed in commit
> 89c22d8c3b27 ("net: Fix skb csum races when peeking")
> 
> While we are at it, use a helper only dealing with
> udp_skb_scratch(skb)->csum_unnecessary, as this allows
> udp_set_dev_scratch() to be called once and thus inlined.
> 
> [1]
 ...
> Fixes: 2276f58ac589 ("udp: use a separate rx queue for packet reception")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>

Applied and queued up for -stable, thanks Eric.