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[UDP]: Avoid repeated counting of checksum errors due to peeking

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Currently it is possible for two processes to peek on the same socket
and end up incrementing the error counter twice for the same packet.

This patch fixes it by making skb_kill_datagram return whether it
succeeded in unlinking the packet and only incrementing the counter
if it did.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Herbert Xu 2007-12-05 01:51:58 -08:00 committed by David S. Miller
parent c8fecf2242
commit 27ab256864
4 changed files with 13 additions and 7 deletions
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2
include/linux/skbuff.h
View File

@ -1549,7 +1549,7 @@ extern int skb_copy_and_csum_datagram_iovec(struct sk_buff *skb,
int hlen,
struct iovec *iov);
extern void skb_free_datagram(struct sock *sk, struct sk_buff *skb);
extern void skb_kill_datagram(struct sock *sk, struct sk_buff *skb,
extern int skb_kill_datagram(struct sock *sk, struct sk_buff *skb,
unsigned int flags);
extern __wsum skb_checksum(const struct sk_buff *skb, int offset,
int len, __wsum csum);

9
net/core/datagram.c
View File

@ -217,20 +217,27 @@ void skb_free_datagram(struct sock *sk, struct sk_buff *skb)
* This function currently only disables BH when acquiring the
* sk_receive_queue lock. Therefore it must not be used in a
* context where that lock is acquired in an IRQ context.
*
* It returns 0 if the packet was removed by us.
*/
void skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags)
int skb_kill_datagram(struct sock *sk, struct sk_buff *skb, unsigned int flags)
{
int err = 0;
if (flags & MSG_PEEK) {
err = -ENOENT;
spin_lock_bh(&sk->sk_receive_queue.lock);
if (skb == skb_peek(&sk->sk_receive_queue)) {
__skb_unlink(skb, &sk->sk_receive_queue);
atomic_dec(&skb->users);
err = 0;
}
spin_unlock_bh(&sk->sk_receive_queue.lock);
}
kfree_skb(skb);
return err;
}
EXPORT_SYMBOL(skb_kill_datagram);

5
net/ipv4/udp.c
View File

@ -899,9 +899,8 @@ out:
return err;
csum_copy_err:
UDP_INC_STATS_USER(UDP_MIB_INERRORS, is_udplite);
skb_kill_datagram(sk, skb, flags);
if (!skb_kill_datagram(sk, skb, flags))
UDP_INC_STATS_USER(UDP_MIB_INERRORS, is_udplite);
if (noblock)
return -EAGAIN;

4
net/ipv6/udp.c
View File

@ -207,8 +207,8 @@ out:
return err;
csum_copy_err:
UDP6_INC_STATS_USER(UDP_MIB_INERRORS, is_udplite);
skb_kill_datagram(sk, skb, flags);
if (!skb_kill_datagram(sk, skb, flags))
UDP6_INC_STATS_USER(UDP_MIB_INERRORS, is_udplite);
if (flags & MSG_DONTWAIT)
return -EAGAIN;