diff options
| author | Paolo Abeni <pabeni@redhat.com> | 2017-06-23 14:19:51 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-06-23 11:18:43 -0400 |
| commit | 9bd780f5e0663035d41a95a6b87eced011ba7e2a (patch) | |
| tree | 9179096d14dd69ac1cd7355d55d0c4ade8ac0b9e /net/ipv4 | |
| parent | 4b943faedfc29eda882851b772c06cecdf78d8e3 (diff) | |
| download | linux-9bd780f5e0663035d41a95a6b87eced011ba7e2a.tar.gz | |
udp: fix poll()
Michael reported an UDP breakage caused by the commit b65ac44674dd
("udp: try to avoid 2 cache miss on dequeue").
The function __first_packet_length() can update the checksum bits
of the pending skb, making the scratched area out-of-sync, and
setting skb->csum, if the skb was previously in need of checksum
validation.
On later recvmsg() for such skb, checksum validation will be
invoked again - due to the wrong udp_skb_csum_unnecessary()
value - and will fail, causing the valid skb to be dropped.
This change addresses the issue refreshing the scratch area in
__first_packet_length() after the possible checksum update.
Fixes: b65ac44674dd ("udp: try to avoid 2 cache miss on dequeue")
Reported-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4')
| -rw-r--r-- | net/ipv4/udp.c | 27 |
1 files changed, 17 insertions, 10 deletions
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index 067a607917f9..47c7aa0501af 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1446,16 +1446,23 @@ static struct sk_buff *__first_packet_length(struct sock *sk, { struct sk_buff *skb; - while ((skb = skb_peek(rcvq)) != NULL && - udp_lib_checksum_complete(skb)) { - __UDP_INC_STATS(sock_net(sk), UDP_MIB_CSUMERRORS, - IS_UDPLITE(sk)); - __UDP_INC_STATS(sock_net(sk), UDP_MIB_INERRORS, - IS_UDPLITE(sk)); - atomic_inc(&sk->sk_drops); - __skb_unlink(skb, rcvq); - *total += skb->truesize; - kfree_skb(skb); + while ((skb = skb_peek(rcvq)) != NULL) { + if (udp_lib_checksum_complete(skb)) { + __UDP_INC_STATS(sock_net(sk), UDP_MIB_CSUMERRORS, + IS_UDPLITE(sk)); + __UDP_INC_STATS(sock_net(sk), UDP_MIB_INERRORS, + IS_UDPLITE(sk)); + atomic_inc(&sk->sk_drops); + __skb_unlink(skb, rcvq); + *total += skb->truesize; + kfree_skb(skb); + } else { + /* the csum related bits could be changed, refresh + * the scratch area + */ + udp_set_dev_scratch(skb); + break; + } } return skb; } |