diff options
| author | Dominic Curran <dominic.curran@citrix.com> | 2014-01-22 03:03:23 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2014-01-22 21:32:56 -0800 |
| commit | fa35864e0bb7f7c13b9c6d6751ddac9b42d4810f (patch) | |
| tree | 50f705ece98607b7a54161554b486d65c426ac2e /drivers/net/tun.c | |
| parent | bdf4351bbc62f3b24151cf19ca6e531b68d8c340 (diff) | |
| download | lwn-fa35864e0bb7f7c13b9c6d6751ddac9b42d4810f.tar.gz lwn-fa35864e0bb7f7c13b9c6d6751ddac9b42d4810f.zip | |
tuntap: Fix for a race in accessing numqueues
A patch for fixing a race between queue selection and changing queues
was introduced in commit 92bb73ea2("tuntap: fix a possible race between
queue selection and changing queues").
The fix was to prevent the driver from re-reading the tun->numqueues
more than once within tun_select_queue() using ACCESS_ONCE().
We have been experiancing 'Divide-by-zero' errors in tun_net_xmit()
since we moved from 3.6 to 3.10, and believe that they come from a
simular source where the value of tun->numqueues changes to zero
between the first and a subsequent read of tun->numqueues.
The fix is a simular use of ACCESS_ONCE(), as well as a multiply
instead of a divide in the if statement.
Signed-off-by: Dominic Curran <dominic.curran@citrix.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Maxim Krasnyansky <maxk@qti.qualcomm.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Max Krasnyansky <maxk@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/tun.c')
| -rw-r--r-- | drivers/net/tun.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 34cca74c99ed..bcf01af4b879 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -738,15 +738,17 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev) struct tun_struct *tun = netdev_priv(dev); int txq = skb->queue_mapping; struct tun_file *tfile; + u32 numqueues = 0; rcu_read_lock(); tfile = rcu_dereference(tun->tfiles[txq]); + numqueues = ACCESS_ONCE(tun->numqueues); /* Drop packet if interface is not attached */ - if (txq >= tun->numqueues) + if (txq >= numqueues) goto drop; - if (tun->numqueues == 1) { + if (numqueues == 1) { /* Select queue was not called for the skbuff, so we extract the * RPS hash and save it into the flow_table here. */ @@ -779,8 +781,8 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev) /* Limit the number of packets queued by dividing txq length with the * number of queues. */ - if (skb_queue_len(&tfile->socket.sk->sk_receive_queue) - >= dev->tx_queue_len / tun->numqueues) + if (skb_queue_len(&tfile->socket.sk->sk_receive_queue) * numqueues + >= dev->tx_queue_len) goto drop; if (unlikely(skb_orphan_frags(skb, GFP_ATOMIC))) |