[PATCH V3 2/2] virtio-net: sanitize buggy features advertised by host

[Jason Wang]

This patch tries to detect the possible buggy features advertised by host
and sanitize them. One example is booting virtio-net with only ctrl_vq
disabled, qemu may still advertise many features which depends on it. This
will trigger several BUG()s in virtnet_send_command().

This patch utilizes the sanitize_features() method, and disables all
features that depends on ctrl_vq if it was not advertised.

This fixes the crash when booting with ctrl_vq=off using qemu.

Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
Cc: Cornelia Huck <cornelia.huck@xxxxxxxxxx>
Cc: Wanlong Gao <gaowanlong@xxxxxxxxxxxxxx>
Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
---
Changes from V1:
- fix the cut-and-paste error
Changes from V2:
- loop through an array of feature bits
- switch to use dev_warn()
---
 drivers/net/virtio_net.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index ec2a8b4..6fadd8c 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1948,6 +1948,31 @@ static int virtnet_restore(struct virtio_device *vdev)
 }
 #endif
 
+static void virtnet_sanitize_features(struct virtio_device *dev)
+{
+	unsigned int features_for_ctrl_vq[] = {
+		VIRTIO_NET_F_CTRL_RX,
+		VIRTIO_NET_F_CTRL_VLAN,
+		VIRTIO_NET_F_GUEST_ANNOUNCE,
+		VIRTIO_NET_F_MQ,
+		VIRTIO_NET_F_CTRL_MAC_ADDR
+	};
+	int i;
+
+	if (!virtio_has_feature(dev, VIRTIO_NET_F_CTRL_VQ)) {
+		for (i = 0; i < ARRAY_SIZE(features_for_ctrl_vq); i++) {
+			unsigned int f = features_for_ctrl_vq[i];
+			if (virtio_has_feature(dev, f)) {
+				virtio_disable_feature(dev, f);
+				dev_warn(&dev->dev,
+					 "buggy hyperviser: disable feature "
+					 "0x%x since VIRTIO_NET_F_CTRL_VQ was "
+					 "not advertised.\n", f);
+			}
+		}
+	}
+}
+
 static struct virtio_device_id id_table[] = {
 	{ VIRTIO_ID_NET, VIRTIO_DEV_ANY_ID },
 	{ 0 },
@@ -1975,6 +2000,7 @@ static struct virtio_driver virtio_net_driver = {
 	.probe =	virtnet_probe,
 	.remove =	virtnet_remove,
 	.config_changed = virtnet_config_changed,
+	.sanitize_features = virtnet_sanitize_features,
 #ifdef CONFIG_PM_SLEEP
 	.freeze =	virtnet_freeze,
 	.restore =	virtnet_restore,
-- 
1.9.1

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