netdev - Re: [RFC PATCH] udp: don't rereference dst

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Date:	Thu, 07 Mar 2013 14:47:24 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Tom Parkin <tparkin@...alix.com>
Cc:	netdev@...r.kernel.org
Subject: Re: [RFC PATCH] udp: don't rereference dst_entry dev pointer on rcv

On Thu, 2013-03-07 at 22:36 +0000, Tom Parkin wrote:
> When a fragmented IP packet is queued during device teardown, it is possible
> for the reassembled packet to hit the UDP rcv path with a NULL dst_entry dev
> pointer.  Drop such packets to prevent an oops.
> ---
>  net/ipv4/udp.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index 0a073a2..c38a4b1 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -1700,6 +1700,9 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
>  		return __udp4_lib_mcast_deliver(net, skb, uh,
>  				saddr, daddr, udptable);
>  
> +	if (skb_dst(skb)->dev == NULL)
> +		goto drop;
> +
>  	sk = __udp4_lib_lookup_skb(skb, uh->source, uh->dest, udptable);
>  
>  	if (sk != NULL) {


Hmm... couldnt it be tested in reassembly layer instead ?

Why is it specific to UDP ?



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