Re: [PATCH] udp: Fix potential wrong ip_hdr(skb) pointers

[Eric Dumazet <dada1@cosmosbay.com>]

Jesper Dangaard Brouer a écrit :
> On Fri, 2009-02-06 at 01:08 -0800, David Miller wrote:
>> Please respin this patch of your's with proper commit message
>> and signoffs, thanks!
> 
> Like the UDP header fix, pskb_may_pull() can potentially
> alter the SKB buffer.  Thus the saddr and daddr, pointers
> may point to the old skb->data buffer.
> 

I dont know... daddr and saddr are not pointers but integers.

Patch makes sense as a cleanup, but ChangeLog seems wrong ?

> I haven't seen corruptions, as its only seen if the old
> skb->data buffer were reallocated by another user and
> written into very quickly (or poison'd by SLAB debugging).
> 
> Signed-off-by: Jesper Dangaard Brouer <hawk@comx.dk>
> ---
> 
>  net/ipv4/udp.c |    6 ++++--
>  1 files changed, 4 insertions(+), 2 deletions(-)
> 
> 
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index cc3a0a0..c47c989 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -1234,8 +1234,7 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
>  	struct udphdr *uh;
>  	unsigned short ulen;
>  	struct rtable *rt = (struct rtable*)skb->dst;
> -	__be32 saddr = ip_hdr(skb)->saddr;
> -	__be32 daddr = ip_hdr(skb)->daddr;
> +	__be32 saddr, daddr;
>  	struct net *net = dev_net(skb->dev);
>  
>  	/*
> @@ -1259,6 +1258,9 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
>  	if (udp4_csum_init(skb, uh, proto))
>  		goto csum_error;
>  
> +	saddr = ip_hdr(skb)->saddr;
> +	daddr = ip_hdr(skb)->daddr;
> +
>  	if (rt->rt_flags & (RTCF_BROADCAST|RTCF_MULTICAST))
>  		return __udp4_lib_mcast_deliver(net, skb, uh,
>  				saddr, daddr, udptable);
> 
>