Commit 028b0275 authored by Patrick McHardy's avatar Patrick McHardy Committed by David S. Miller
Browse files

[DCCP]: Fix skb->cb conflicts with IP 



dev_queue_xmit() and the other IP output functions expect to get a skb
with clear or properly initialized skb->cb. Unlike TCP and UDP, the
dccp_skb_cb doesn't contain a struct inet_skb_parm at the beginning,
so the DCCP-specific data is interpreted by the IP output functions.
This can cause false negatives for the conditional POST_ROUTING hook
invocation, making the packet bypass the hook.

Add a inet_skb_parm/inet6_skb_parm union to the beginning of
dccp_skb_cb to avoid clashes. Also add a BUILD_BUG_ON to make
sure it fits in the cb.

[ Combined with patch from Gerrit Renker to remove two now unnecessary
  memsets of IPCB(skb)->opt ]

Signed-off-by: default avatarPatrick McHardy <kaber@trash.net>
Acked-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ae1b6a31

net/dccp/dccp.h

+6 −0
Original line number Diff line number Diff line
@@ -325,6 +325,12 @@ static inline int dccp_bad_service_code(const struct sock *sk, 
 * This is used for transmission as well as for reception.

 */

struct dccp_skb_cb {

	union {

		struct inet_skb_parm	h4;

#if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)

		struct inet6_skb_parm	h6;

#endif

	} header;

	__u8  dccpd_type:4;

	__u8  dccpd_ccval:4;

	__u8  dccpd_reset_code,

net/dccp/ipv4.c

+0 −1
Original line number Diff line number Diff line
@@ -489,7 +489,6 @@ static int dccp_v4_send_response(struct sock *sk, struct request_sock *req, 


		dh->dccph_checksum = dccp_v4_csum_finish(skb, ireq->loc_addr,

							      ireq->rmt_addr);

		memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));

		err = ip_build_and_send_pkt(skb, sk, ireq->loc_addr,

					    ireq->rmt_addr,

					    ireq->opt);

net/dccp/output.c

+0 −1
Original line number Diff line number Diff line
@@ -126,7 +126,6 @@ static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb) 


		DCCP_INC_STATS(DCCP_MIB_OUTSEGS);



		memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));

		err = icsk->icsk_af_ops->queue_xmit(skb, 0);

		return net_xmit_eval(err);

	}

net/dccp/proto.c

+3 −0
Original line number Diff line number Diff line
@@ -1057,6 +1057,9 @@ static int __init dccp_init(void) 
	int ehash_order, bhash_order, i;

	int rc = -ENOBUFS;



	BUILD_BUG_ON(sizeof(struct dccp_skb_cb) >

		     FIELD_SIZEOF(struct sk_buff, cb));



	dccp_hashinfo.bind_bucket_cachep =

		kmem_cache_create("dccp_bind_bucket",

				  sizeof(struct inet_bind_bucket), 0,

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