xen-netback: avoid race that can lead to NULL pointer dereference (fd42bfd1) · Commits · 戴 / test

In function xenvif_disconnect_queue(), the value of queue->rx_irq is zeroed *before* queue->task is stopped. Unfortunately that task may call notify_remote_via_irq(queue->rx_irq) and calling that function with a zero value results in a NULL pointer dereference in evtchn_from_irq(). This patch simply re-orders things, stopping all tasks before zero-ing the irq values, thereby avoiding the possibility of the race. Fixes: ("xen/netback: cleanup init and deinit code") Signed-off-by:

Paul Durrant <pdurrant@amazon.com> Acked-by:

Wei Liu <wei.liu@kernel.org> Signed-off-by:

Jakub Kicinski <jakub.kicinski@netronome.com>

drivers/net/xen-netback/interface.c

+12 −12

Original line number	Diff line number	Diff line
		@@ -628,18 +628,6 @@ err:

		static void xenvif_disconnect_queue(struct xenvif_queue *queue)
		{
		if (queue->tx_irq) {
		unbind_from_irqhandler(queue->tx_irq, queue);
		if (queue->tx_irq == queue->rx_irq)
		queue->rx_irq = 0;
		queue->tx_irq = 0;
		}

		if (queue->rx_irq) {
		unbind_from_irqhandler(queue->rx_irq, queue);
		queue->rx_irq = 0;
		}

		if (queue->task) {
		kthread_stop(queue->task);
		queue->task = NULL;
		@@ -655,6 +643,18 @@ static void xenvif_disconnect_queue(struct xenvif_queue *queue)
		queue->napi.poll = NULL;
		}

		if (queue->tx_irq) {
		unbind_from_irqhandler(queue->tx_irq, queue);
		if (queue->tx_irq == queue->rx_irq)
		queue->rx_irq = 0;
		queue->tx_irq = 0;
		}

		if (queue->rx_irq) {
		unbind_from_irqhandler(queue->rx_irq, queue);
		queue->rx_irq = 0;
		}

		xenvif_unmap_frontend_data_rings(queue);
		}

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