[PATCH net 1/2] vhost: check owner before we overwrite ubuf_info

[Michael S. Tsirkin]

If device has an owner, we shouldn't touch ubuf_info
since it might be in use.

Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
 drivers/vhost/net.c   | 4 ++++
 drivers/vhost/vhost.c | 8 +++++++-
 drivers/vhost/vhost.h | 1 +
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 2b51e23..6b00f64 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -1053,6 +1053,10 @@ static long vhost_net_set_owner(struct vhost_net *n)
 	int r;
 
 	mutex_lock(&n->dev.mutex);
+	if (vhost_dev_has_owner(&n->dev)) {
+		r = -EBUSY;
+		goto out;
+	}
 	r = vhost_net_set_ubuf_info(n);
 	if (r)
 		goto out;
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index beee7f5..60aa5ad 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -344,13 +344,19 @@ static int vhost_attach_cgroups(struct vhost_dev *dev)
 }
 
 /* Caller should have device mutex */
+bool vhost_dev_has_owner(struct vhost_dev *dev)
+{
+	return dev->mm;
+}
+
+/* Caller should have device mutex */
 long vhost_dev_set_owner(struct vhost_dev *dev)
 {
 	struct task_struct *worker;
 	int err;
 
 	/* Is there an owner already? */
-	if (dev->mm) {
+	if (vhost_dev_has_owner(dev)) {
 		err = -EBUSY;
 		goto err_mm;
 	}
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index a7ad635..64adcf9 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -133,6 +133,7 @@ struct vhost_dev {
 
 long vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue **vqs, int nvqs);
 long vhost_dev_set_owner(struct vhost_dev *dev);
+bool vhost_dev_has_owner(struct vhost_dev *dev);
 long vhost_dev_check_owner(struct vhost_dev *);
 struct vhost_memory *vhost_dev_reset_owner_prepare(void);
 void vhost_dev_reset_owner(struct vhost_dev *, struct vhost_memory *);
-- 
MST

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