lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Wed, 22 Jan 2014 11:44:22 -0800 From: Max Krasnyansky <maxk@....qualcomm.com> To: Dominic Curran <dominic.curran@...rix.com>, <netdev@...r.kernel.org> CC: Jason Wang <jasowang@...hat.com> Subject: Re: [PATCH net-next v3] tuntap: Fix for a race in accessing numqueues On 01/21/2014 07:03 PM, Dominic Curran wrote: > 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@...rix.com> > Cc: Jason Wang <jasowang@...hat.com> > Cc: Maxim Krasnyansky <maxk@....qualcomm.com> > --- > V3: Rebase against net-next. Include all numqueues in function. > V2: Use multiply instead of divide. Suggested by Eric Dumazet. > Fixed email address for maxk. Rebase against net tree. > --- > drivers/net/tun.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > Index: net-next/drivers/net/tun.c > =================================================================== > --- net-next.orig/drivers/net/tun.c 2014-01-22 02:50:01.000000000 +0000 > +++ net-next/drivers/net/tun.c 2014-01-22 02:59:42.000000000 +0000 > @@ -738,15 +738,17 @@ static netdev_tx_t tun_net_xmit(struct s > 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 s > /* 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))) > Acked-by: Max Krasnyansky <maxk@...nel.org> -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Powered by blists - more mailing lists