netdev - [PATCH 2/4] virtio_net: add a timeout in virtnet_send

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Date:   Sun, 22 Jan 2023 11:05:24 +0100
From:   Laurent Vivier <lvivier@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Parav Pandit <parav@...dia.com>,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        Eli Cohen <elic@...dia.com>, Jason Wang <jasowang@...hat.com>,
        Gautam Dawar <gautam.dawar@...inx.com>,
        Cindy Lu <lulu@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eugenio Pérez <eperezma@...hat.com>
Subject: [PATCH 2/4] virtio_net: add a timeout in virtnet_send_command()

if the device control queue is buggy, don't crash the kernel by
waiting for ever the response.

Signed-off-by: Laurent Vivier <lvivier@...hat.com>
---
 drivers/net/virtio_net.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 25511a86590e..29b3cc72082d 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1974,6 +1974,7 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
 	struct scatterlist *sgs[4], hdr, stat;
 	unsigned out_num = 0, tmp;
 	int ret;
+	unsigned long timeout;
 
 	/* Caller should know better */
 	BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ));
@@ -2006,8 +2007,10 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
 	/* Spin for a response, the kick causes an ioport write, trapping
 	 * into the hypervisor, so the request should be handled immediately.
 	 */
+	timeout = jiffies + 20 * HZ;
 	while (!virtqueue_get_buf(vi->cvq, &tmp) &&
-	       !virtqueue_is_broken(vi->cvq))
+	       !virtqueue_is_broken(vi->cvq) &&
+	       !time_after(jiffies, timeout))
 		cpu_relax();
 
 	return vi->ctrl->status == VIRTIO_NET_OK;
-- 
2.39.0