From 4b7fd2e688d51f8ed7380758047fcaa4d4693d47 Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Wed, 15 Oct 2014 16:23:28 +0300 Subject: [PATCH] virtio_net: fix use after free commit 0b725a2ca61bedc33a2a63d0451d528b268cf975 net: Remove ndo_xmit_flush netdev operation, use signalling instead. added code that looks at skb->xmit_more after the skb has been put in TX VQ. Since some paths process the ring and free the skb immediately, this can cause use after free. Fix by storing xmit_more in a local variable. Cc: David S. Miller Signed-off-by: Michael S. Tsirkin Signed-off-by: David S. Miller --- drivers/net/virtio_net.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 3d0ce4468ce6..13d0a8bc8bf3 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -920,6 +920,8 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) int qnum = skb_get_queue_mapping(skb); struct send_queue *sq = &vi->sq[qnum]; int err; + struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum); + bool kick = !skb->xmit_more; /* Free up any pending old buffers before queueing new ones. */ free_old_xmit_skbs(sq); @@ -956,7 +958,7 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) } } - if (__netif_subqueue_stopped(dev, qnum) || !skb->xmit_more) + if (kick || netif_xmit_stopped(txq)) virtqueue_kick(sq->vq); return NETDEV_TX_OK; -- 2.20.1