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authorAaron Knister <aaron.s.knister@nasa.gov>2018-08-24 08:42:46 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-09-26 08:35:07 +0200
commitee4d1a30a4dd851aa31488ac77bfdd9ae6ae2556 (patch)
tree001241421d8c16a10130ceec331be82fe79ebc39
parenta739cb3e04a2f87bf29119a61cb2f77483ae228b (diff)
IB/ipoib: Avoid a race condition between start_xmit and cm_rep_handler
commit 816e846c2eb9129a3e0afa5f920c8bbc71efecaa upstream. Inside of start_xmit() the call to check if the connection is up and the queueing of the packets for later transmission is not atomic which leaves a window where cm_rep_handler can run, set the connection up, dequeue pending packets and leave the subsequently queued packets by start_xmit() sitting on neigh->queue until they're dropped when the connection is torn down. This only applies to connected mode. These dropped packets can really upset TCP, for example, and cause multi-minute delays in transmission for open connections. Here's the code in start_xmit where we check to see if the connection is up: if (ipoib_cm_get(neigh)) { if (ipoib_cm_up(neigh)) { ipoib_cm_send(dev, skb, ipoib_cm_get(neigh)); goto unref; } } The race occurs if cm_rep_handler execution occurs after the above connection check (specifically if it gets to the point where it acquires priv->lock to dequeue pending skb's) but before the below code snippet in start_xmit where packets are queued. if (skb_queue_len(&neigh->queue) < IPOIB_MAX_PATH_REC_QUEUE) { push_pseudo_header(skb, phdr->hwaddr); spin_lock_irqsave(&priv->lock, flags); __skb_queue_tail(&neigh->queue, skb); spin_unlock_irqrestore(&priv->lock, flags); } else { ++dev->stats.tx_dropped; dev_kfree_skb_any(skb); } The patch acquires the netif tx lock in cm_rep_handler for the section where it sets the connection up and dequeues and retransmits deferred skb's. Fixes: 839fcaba355a ("IPoIB: Connected mode experimental support") Cc: stable@vger.kernel.org Signed-off-by: Aaron Knister <aaron.s.knister@nasa.gov> Tested-by: Ira Weiny <ira.weiny@intel.com> Reviewed-by: Ira Weiny <ira.weiny@intel.com> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/infiniband/ulp/ipoib/ipoib_cm.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/infiniband/ulp/ipoib/ipoib_cm.c b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
index f74b11542603..a338e60836ee 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_cm.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
@@ -992,12 +992,14 @@ static int ipoib_cm_rep_handler(struct ib_cm_id *cm_id, struct ib_cm_event *even
skb_queue_head_init(&skqueue);
+ netif_tx_lock_bh(p->dev);
spin_lock_irq(&priv->lock);
set_bit(IPOIB_FLAG_OPER_UP, &p->flags);
if (p->neigh)
while ((skb = __skb_dequeue(&p->neigh->queue)))
__skb_queue_tail(&skqueue, skb);
spin_unlock_irq(&priv->lock);
+ netif_tx_unlock_bh(p->dev);
while ((skb = __skb_dequeue(&skqueue))) {
skb->dev = p->dev;