netdev - Re: [PATCH net] ip: on queued skb use skb_header_pointer instead of pskb_may

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Message-Id: <20190110.062824.723694604441608510.davem@davemloft.net>
Date:   Thu, 10 Jan 2019 06:28:24 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     willemdebruijn.kernel@...il.com
Cc:     netdev@...r.kernel.org, edumazet@...gle.co, willemb@...gle.com,
        syzkaller@...glegroups.com, edumazet@...gle.com
Subject: Re: [PATCH net] ip: on queued skb use skb_header_pointer instead
 of pskb_may_pull

From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Date: Mon,  7 Jan 2019 16:47:33 -0500

> From: Willem de Bruijn <willemb@...gle.com>
> 
> Commit 2efd4fca703a ("ip: in cmsg IP(V6)_ORIGDSTADDR call
> pskb_may_pull") avoided a read beyond the end of the skb linear
> segment by calling pskb_may_pull.
> 
> That function can trigger a BUG_ON in pskb_expand_head if the skb is
> shared, which it is when when peeking. It can also return ENOMEM.
> 
> Avoid both by switching to safer skb_header_pointer.
> 
> Fixes: 2efd4fca703a ("ip: in cmsg IP(V6)_ORIGDSTADDR call pskb_may_pull")
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Suggested-by: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>

Applied and queued up for -stable.