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authorPaul Durrant <pdurrant@amazon.com>2019-12-13 13:20:40 +0000
committerJakub Kicinski <jakub.kicinski@netronome.com>2019-12-15 11:40:15 -0800
commitfd42bfd1bb31f9a521be6b4f1bd89b85abc08d20 (patch)
tree9bdcee15484dd3a8c51acf9a7e52c24335eb82b4
parent858ce8ca62ea1530f2779d0e3f934b0176e663c3 (diff)
downloadlinux-fd42bfd1bb31f9a521be6b4f1bd89b85abc08d20.tar.bz2
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: 2ac061ce97f4 ("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>
-rw-r--r--drivers/net/xen-netback/interface.c24
1 files changed, 12 insertions, 12 deletions
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 68dd7bb07ca6..f15ba3de6195 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -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);
}