Commit 415787d7 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

ipv6: frags: fix a lockdep false positive 



lockdep does not know that the locks used by IPv4 defrag
and IPv6 reassembly units are of different classes.

It complains because of following chains :

1) sch_direct_xmit()        (lock txq->_xmit_lock)
    dev_hard_start_xmit()
     xmit_one()
      dev_queue_xmit_nit()
       packet_rcv_fanout()
        ip_check_defrag()
         ip_defrag()
          spin_lock()     (lock frag queue spinlock)

2) ip6_input_finish()
    ipv6_frag_rcv()       (lock frag queue spinlock)
     ip6_frag_queue()
      icmpv6_param_prob() (lock txq->_xmit_lock at some point)

We could add lockdep annotations, but we also can make sure IPv6
calls icmpv6_param_prob() only after the release of the frag queue spinlock,
since this naturally makes frag queue spinlock a leaf in lock hierarchy.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0dcec221

net/ipv6/reassembly.c

+12 −11
Original line number Diff line number Diff line
@@ -163,7 +163,8 @@ fq_find(struct net *net, __be32 id, const struct ipv6hdr *hdr, int iif) 
}



static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb,

			   struct frag_hdr *fhdr, int nhoff)

			  struct frag_hdr *fhdr, int nhoff,

			  u32 *prob_offset)

{

	struct sk_buff *prev, *next;

	struct net_device *dev;
@@ -179,11 +180,7 @@ static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb, 
			((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));



	if ((unsigned int)end > IPV6_MAXPLEN) {

		__IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),

				IPSTATS_MIB_INHDRERRORS);

		icmpv6_param_prob(skb, ICMPV6_HDR_FIELD,

				  ((u8 *)&fhdr->frag_off -

				   skb_network_header(skb)));

		*prob_offset = (u8 *)&fhdr->frag_off - skb_network_header(skb);

		return -1;

	}
@@ -214,10 +211,7 @@ static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb, 
			/* RFC2460 says always send parameter problem in

			 * this case. -DaveM

			 */

			__IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),

					IPSTATS_MIB_INHDRERRORS);

			icmpv6_param_prob(skb, ICMPV6_HDR_FIELD,

					  offsetof(struct ipv6hdr, payload_len));

			*prob_offset = offsetof(struct ipv6hdr, payload_len);

			return -1;

		}

		if (end > fq->q.len) {
@@ -519,15 +513,22 @@ static int ipv6_frag_rcv(struct sk_buff *skb) 
	iif = skb->dev ? skb->dev->ifindex : 0;

	fq = fq_find(net, fhdr->identification, hdr, iif);

	if (fq) {

		u32 prob_offset = 0;

		int ret;



		spin_lock(&fq->q.lock);



		fq->iif = iif;

		ret = ip6_frag_queue(fq, skb, fhdr, IP6CB(skb)->nhoff);

		ret = ip6_frag_queue(fq, skb, fhdr, IP6CB(skb)->nhoff,

				     &prob_offset);



		spin_unlock(&fq->q.lock);

		inet_frag_put(&fq->q);

		if (prob_offset) {

			__IP6_INC_STATS(net, __in6_dev_get_safely(skb->dev),

					IPSTATS_MIB_INHDRERRORS);

			icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, prob_offset);

		}

		return ret;

	}

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