netdev - Re: ipv6_mc_check_mld - kernel BUG at net/core/skbuff.c:1128

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Date:	Tue, 11 Aug 2015 22:51:40 +0200
From:	Linus Lüssing <linus.luessing@...3.blue>
To:	Brenden Blanco <bblanco@...mgrid.com>
Cc:	netdev@...r.kernel.org
Subject: Re: ipv6_mc_check_mld - kernel BUG at net/core/skbuff.c:1128

On Mon, Aug 10, 2015 at 02:56:12PM -0700, Brenden Blanco wrote:
> Doing some code reading with Alexei, we found a suspect commit, which
> introduces an skb_get and skb_may_pull of the same skb, which leads to the BUG
> when skb->len == len.

Urgh, didn't know that pskb_may_pull() doesn't like an skb with a
reference count greater than one... But yes, the BUG() call in
skbuff.c:1128 / pskb_expand_head() says that (though in this case
the BUG() in skbuff.c call actually seems kinda weird (/"wrong"?), as
it isn't shared between different code paths).

Thanks for the thorough analysis, going to provide a patch within
the next 24h (hopefully).

Cheers, Linus
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