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[PULL,V2,3/3] net: forbid the reentrant RX

Message ID 1595927419-27346-4-git-send-email-jasowang@redhat.com
State New
Headers show
Series [PULL,V2,1/3] virtio-pci: fix wrong index in virtio_pci_queue_enabled | expand

Commit Message

Jason Wang July 28, 2020, 9:10 a.m. UTC
The memory API allows DMA into NIC's MMIO area. This means the NIC's
RX routine must be reentrant. Instead of auditing all the NIC, we can
simply detect the reentrancy and return early. The queue->delivering
is set and cleared by qemu_net_queue_deliver() for other queue helpers
to know whether the delivering in on going (NIC's receive is being
called). We can check it and return early in qemu_net_queue_flush() to
forbid reentrant RX.

Signed-off-by: Jason Wang <jasowang@redhat.com>
 net/queue.c | 3 +++
 1 file changed, 3 insertions(+)
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diff --git a/net/queue.c b/net/queue.c
index 0164727..19e32c8 100644
--- a/net/queue.c
+++ b/net/queue.c
@@ -250,6 +250,9 @@  void qemu_net_queue_purge(NetQueue *queue, NetClientState *from)
 bool qemu_net_queue_flush(NetQueue *queue)
+    if (queue->delivering)
+        return false;
     while (!QTAILQ_EMPTY(&queue->packets)) {
         NetPacket *packet;
         int ret;