4.7-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ Upstream commit e83c6744e81abc93a20d0eb3b7f504a176a6126a ]
Laura tracked poll() [and friends] regression caused by commit
e6afc8ace6dd ("udp: remove headers from UDP packets before queueing")
udp_poll() needs to know if there is a valid packet in receive queue,
even if its payload length is 0.
Change first_packet_length() to return an signed int, and use -1
as the indication of an empty queue.
Fixes: e6afc8ace6dd ("udp: remove headers from UDP packets before queueing")
Reported-by: Laura Abbott <labbott@xxxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Tested-by: Laura Abbott <labbott@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/ipv4/udp.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1182,13 +1182,13 @@ out:
* @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.
+ * Returns the length of found skb, or -1 if none is found.
*/
-static unsigned int first_packet_length(struct sock *sk)
+static 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;
+ int res;
__skb_queue_head_init(&list_kill);
@@ -1203,7 +1203,7 @@ static unsigned int first_packet_length(
__skb_unlink(skb, rcvq);
__skb_queue_tail(&list_kill, skb);
}
- res = skb ? skb->len : 0;
+ res = skb ? skb->len : -1;
spin_unlock_bh(&rcvq->lock);
if (!skb_queue_empty(&list_kill)) {
@@ -1232,7 +1232,7 @@ int udp_ioctl(struct sock *sk, int cmd,
case SIOCINQ:
{
- unsigned int amount = first_packet_length(sk);
+ int amount = max_t(int, 0, first_packet_length(sk));
return put_user(amount, (int __user *)arg);
}
@@ -2184,7 +2184,7 @@ unsigned int udp_poll(struct file *file,
/* Check for false positives due to checksum errors */
if ((mask & POLLRDNORM) && !(file->f_flags & O_NONBLOCK) &&
- !(sk->sk_shutdown & RCV_SHUTDOWN) && !first_packet_length(sk))
+ !(sk->sk_shutdown & RCV_SHUTDOWN) && first_packet_length(sk) == -1)
mask &= ~(POLLIN | POLLRDNORM);
return mask;
--
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