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udp: Fix udp_poll() and ioctl()

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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 95766fff6b
([UDP]: Add memory accounting.)

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

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2009-10-09 04:43:40 +00:00 committed by David S. Miller
parent 9652041da1
commit 8558467201
1 changed files with 43 additions and 30 deletions
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73
net/ipv4/udp.c
View File

@ -841,6 +841,42 @@ out:
return ret; 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 * IOCTL requests applicable to the UDP protocol
*/ */
@ -857,21 +893,16 @@ int udp_ioctl(struct sock *sk, int cmd, unsigned long arg)
case SIOCINQ: case SIOCINQ:
{ {
struct sk_buff *skb; unsigned int amount = first_packet_length(sk);
unsigned long amount;
amount = 0; if (amount)
spin_lock_bh(&sk->sk_receive_queue.lock);
skb = skb_peek(&sk->sk_receive_queue);
if (skb != NULL) {
/* /*
* We will only return the amount * We will only return the amount
* of this packet since that is all * of this packet since that is all
* that will be read. * that will be read.
*/ */
amount = skb->len - sizeof(struct udphdr); amount -= sizeof(struct udphdr);
}
spin_unlock_bh(&sk->sk_receive_queue.lock);
return put_user(amount, (int __user *)arg); 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); unsigned int mask = datagram_poll(file, sock, wait);
struct sock *sk = sock->sk; struct sock *sk = sock->sk;
int is_lite = IS_UDPLITE(sk);
/* Check for false positives due to checksum errors */ /* Check for false positives due to checksum errors */
if ((mask & POLLRDNORM) && if ((mask & POLLRDNORM) && !(file->f_flags & O_NONBLOCK) &&
!(file->f_flags & O_NONBLOCK) && !(sk->sk_shutdown & RCV_SHUTDOWN) && !first_packet_length(sk))
!(sk->sk_shutdown & RCV_SHUTDOWN)) { mask &= ~(POLLIN | POLLRDNORM);
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)
mask &= ~(POLLIN | POLLRDNORM);
}
return mask; return mask;