Commit fd42bfd1 authored by Paul Durrant's avatar Paul Durrant Committed by Jakub Kicinski

xen-netback: avoid race that can lead to NULL pointer dereference

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: 2ac061ce ("xen/netback: cleanup init and deinit code")
Signed-off-by: default avatarPaul Durrant <pdurrant@amazon.com>
Acked-by: default avatarWei Liu <wei.liu@kernel.org>
Signed-off-by: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
parent 858ce8ca
...@@ -628,18 +628,6 @@ int xenvif_connect_ctrl(struct xenvif *vif, grant_ref_t ring_ref, ...@@ -628,18 +628,6 @@ int xenvif_connect_ctrl(struct xenvif *vif, grant_ref_t ring_ref,
static void xenvif_disconnect_queue(struct xenvif_queue *queue) 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) { if (queue->task) {
kthread_stop(queue->task); kthread_stop(queue->task);
queue->task = NULL; queue->task = NULL;
...@@ -655,6 +643,18 @@ static void xenvif_disconnect_queue(struct xenvif_queue *queue) ...@@ -655,6 +643,18 @@ static void xenvif_disconnect_queue(struct xenvif_queue *queue)
queue->napi.poll = NULL; 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); xenvif_unmap_frontend_data_rings(queue);
} }
......
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