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Commit cf0a018a authored by Patrick McHardy's avatar Patrick McHardy Committed by David S. Miller
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netlink: add netlink_skb_set_owner_r() 



For mmap'ed I/O a netlink specific skb destructor needs to be invoked
after the final kfree_skb() to clean up state. This doesn't work currently
since the skb's ownership is transfered to the receiving socket using
skb_set_owner_r(), which orphans the skb, thereby invoking the destructor
prematurely.

Since netlink doesn't account skbs to the originating socket, there's no
need to orphan the skb. Add a netlink specific skb_set_owner_r() variant
that does not orphan the skb and use a netlink specific destructor to
call sock_rfree().

Signed-off-by: default avatarPatrick McHardy <kaber@trash.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1298ca46

net/netlink/af_netlink.c

+17 −3
Original line number Diff line number Diff line
@@ -119,6 +119,20 @@ static void netlink_consume_callback(struct netlink_callback *cb) 
	kfree(cb);

}



static void netlink_skb_destructor(struct sk_buff *skb)

{

	sock_rfree(skb);

}



static void netlink_skb_set_owner_r(struct sk_buff *skb, struct sock *sk)

{

	WARN_ON(skb->sk != NULL);

	skb->sk = sk;

	skb->destructor = netlink_skb_destructor;

	atomic_add(skb->truesize, &sk->sk_rmem_alloc);

	sk_mem_charge(sk, skb->truesize);

}



static void netlink_sock_destruct(struct sock *sk)

{

	struct netlink_sock *nlk = nlk_sk(sk);
@@ -820,7 +834,7 @@ int netlink_attachskb(struct sock *sk, struct sk_buff *skb, 
		}

		return 1;

	}

	skb_set_owner_r(skb, sk);

	netlink_skb_set_owner_r(skb, sk);

	return 0;

}
@@ -890,7 +904,7 @@ static int netlink_unicast_kernel(struct sock *sk, struct sk_buff *skb, 
	ret = -ECONNREFUSED;

	if (nlk->netlink_rcv != NULL) {

		ret = skb->len;

		skb_set_owner_r(skb, sk);

		netlink_skb_set_owner_r(skb, sk);

		NETLINK_CB(skb).sk = ssk;

		nlk->netlink_rcv(skb);

		consume_skb(skb);
@@ -962,7 +976,7 @@ static int netlink_broadcast_deliver(struct sock *sk, struct sk_buff *skb) 


	if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf &&

	    !test_bit(NETLINK_CONGESTED, &nlk->state)) {

		skb_set_owner_r(skb, sk);

		netlink_skb_set_owner_r(skb, sk);

		__netlink_sendskb(sk, skb);

		return atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1);

	}