Commit 85584672 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

udp: Fix udp_poll() and ioctl() 



udp_poll() can in some circumstances drop frames with incorrect checksums.

Problem is we now have to lock the socket while dropping frames, or risk
sk_forward corruption.

This bug is present since commit 95766fff
([UDP]: Add memory accounting.)

While we are at it, we can correct ioctl(SIOCINQ) to also drop bad frames.

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9652041d

net/ipv4/udp.c

+43 −30
Original line number Diff line number Diff line
@@ -841,6 +841,42 @@ out: 
	return ret;

}





/**

 *	first_packet_length	- return length of first packet in receive queue

 *	@sk: socket

 *

 *	Drops all bad checksum frames, until a valid one is found.

 *	Returns the length of found skb, or 0 if none is found.

 */

static unsigned int first_packet_length(struct sock *sk)

{

	struct sk_buff_head list_kill, *rcvq = &sk->sk_receive_queue;

	struct sk_buff *skb;

	unsigned int res;



	__skb_queue_head_init(&list_kill);



	spin_lock_bh(&rcvq->lock);

	while ((skb = skb_peek(rcvq)) != NULL &&

		udp_lib_checksum_complete(skb)) {

		UDP_INC_STATS_BH(sock_net(sk), UDP_MIB_INERRORS,

				 IS_UDPLITE(sk));

		__skb_unlink(skb, rcvq);

		__skb_queue_tail(&list_kill, skb);

	}

	res = skb ? skb->len : 0;

	spin_unlock_bh(&rcvq->lock);



	if (!skb_queue_empty(&list_kill)) {

		lock_sock(sk);

		__skb_queue_purge(&list_kill);

		sk_mem_reclaim_partial(sk);

		release_sock(sk);

	}

	return res;

}



/*

 *	IOCTL requests applicable to the UDP protocol

 */
@@ -857,21 +893,16 @@ int udp_ioctl(struct sock *sk, int cmd, unsigned long arg) 


	case SIOCINQ:

	{

		struct sk_buff *skb;

		unsigned long amount;

		unsigned int amount = first_packet_length(sk);



		amount = 0;

		spin_lock_bh(&sk->sk_receive_queue.lock);

		skb = skb_peek(&sk->sk_receive_queue);

		if (skb != NULL) {

		if (amount)

			/*

			 * We will only return the amount

			 * of this packet since that is all

			 * that will be read.

			 */

			amount = skb->len - sizeof(struct udphdr);

		}

		spin_unlock_bh(&sk->sk_receive_queue.lock);

			amount -= sizeof(struct udphdr);



		return put_user(amount, (int __user *)arg);

	}
@@ -1540,29 +1571,11 @@ unsigned int udp_poll(struct file *file, struct socket *sock, poll_table *wait) 
{

	unsigned int mask = datagram_poll(file, sock, wait);

	struct sock *sk = sock->sk;

	int 	is_lite = IS_UDPLITE(sk);



	/* Check for false positives due to checksum errors */

	if ((mask & POLLRDNORM) &&

	    !(file->f_flags & O_NONBLOCK) &&

	    !(sk->sk_shutdown & RCV_SHUTDOWN)) {

		struct sk_buff_head *rcvq = &sk->sk_receive_queue;

		struct sk_buff *skb;



		spin_lock_bh(&rcvq->lock);

		while ((skb = skb_peek(rcvq)) != NULL &&

		       udp_lib_checksum_complete(skb)) {

			UDP_INC_STATS_BH(sock_net(sk),

					UDP_MIB_INERRORS, is_lite);

			__skb_unlink(skb, rcvq);

			kfree_skb(skb);

		}

		spin_unlock_bh(&rcvq->lock);



		/* nothing to see, move along */

		if (skb == NULL)

	if ((mask & POLLRDNORM) && !(file->f_flags & O_NONBLOCK) &&

	    !(sk->sk_shutdown & RCV_SHUTDOWN) && !first_packet_length(sk))

		mask &= ~(POLLIN | POLLRDNORM);

	}



	return mask;

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