netdev - Re: [PATCH] netlink: fix compat recvmsg

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Date:	Mon, 16 Aug 2010 14:54:39 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Kalle Valo <kalle.valo@....fi>
Subject: Re: [PATCH] netlink: fix compat recvmsg

On Mon, 2010-08-16 at 14:50 +0200, Eric Dumazet wrote:

> > Additionally, while preparing this patch I found
> > that since none of the remaining netlink code is
> > really aware of the frag_list, we need to use the
> > original skb's information for packet information
> > and credentials. This fixes, for example, the
> > group information received by compat tasks.

> As a side effect, it might fix the 
> 
> 	if (nlk->flags & NETLINK_RECV_PKTINFO)
> 		netlink_cmsg_recv_pktinfo(msg, skb);
> 
> That tried to use pktinfo from the slave skb. After this
> patch, skb points to master skb.

Yeah, that's what I was looking at regarding the "packet information" I
wrote about. The group information was wrong (0 rather than 1), I could
see that in strace (though I had to compile a strace64 binary first...)

> Acked-by: Eric Dumazet <eric.dumazet@...il.com>
> 
> Thanks !

Thanks for looking, and finding the bug to start with :-)

johannes

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