netdev - Re: [PATCH net-next] net: gro: properly remove skb from list

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Message-Id: <20180712.170228.2165629850660879756.davem@davemloft.net>
Date:   Thu, 12 Jul 2018 17:02:28 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     bhole_prashant_q7@....ntt.co.jp
Cc:     brouer@...hat.com, tyhicks@...onical.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net: gro: properly remove skb from list

From: Prashant Bhole <bhole_prashant_q7@....ntt.co.jp>
Date: Thu, 12 Jul 2018 16:24:59 +0900

> Following crash occurs in validate_xmit_skb_list() when same skb is
> iterated multiple times in the loop and consume_skb() is called.
> 
> The root cause is calling list_del_init(&skb->list) and not clearing
> skb->next in d4546c2509b1. list_del_init(&skb->list) sets skb->next
> to point to skb itself. skb->next needs to be cleared because other
> parts of network stack uses another kind of SKB lists.
> validate_xmit_skb_list() uses such list.
> 
> A similar type of bugfix was reported by Jesper Dangaard Brouer.
> https://patchwork.ozlabs.org/patch/942541/
> 
> This patch clears skb->next and changes list_del_init() to list_del()
> so that list->prev will maintain the list poison.
 ...
> Fixes: d4546c2509b1 ("net: Convert GRO SKB handling to list_head.")
> Signed-off-by: Prashant Bhole <bhole_prashant_q7@....ntt.co.jp>
> Reported-by: Tyler Hicks <tyhicks@...onical.com>

Applied, thank you.

Hopefully we can convert more layers to list_head SKB usage, and
thus no longer need hacks like this.

Thanks.