vhost: fix error handling in RESET_OWNER ioctl

RESET_OWNER ioctl would leave the fd in a bad state if
memory allocation failed: device is stopped
but owner is not reset. Make state changes
after allocating memory, such that a failed
ioctl has no effect.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

4 files changed, 24 insertions, 12 deletions

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index e34e195b9cf6..a3645bd163d8 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -967,14 +967,20 @@ static long vhost_net_reset_owner(struct vhost_net *n)
         struct socket *tx_sock = NULL;
         struct socket *rx_sock = NULL;
         long err;
+        struct vhost_memory *memory;
 
         mutex_lock(&n->dev.mutex);
         err = vhost_dev_check_owner(&n->dev);
         if (err)
                 goto done;
+        memory = vhost_dev_reset_owner_prepare();
+        if (!memory) {
+                err = -ENOMEM;
+                goto done;
+        }
         vhost_net_stop(n, &tx_sock, &rx_sock);
         vhost_net_flush(n);
-        err = vhost_dev_reset_owner(&n->dev);
+        vhost_dev_reset_owner(&n->dev, memory);
         vhost_net_vq_reset(n);
 done:
         mutex_unlock(&n->dev.mutex);
diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
index 91d6f060aade..be65414d5bb1 100644
--- a/drivers/vhost/test.c
+++ b/drivers/vhost/test.c
@@ -219,13 +219,20 @@ static long vhost_test_reset_owner(struct vhost_test *n)
 {
         void *priv = NULL;
         long err;
+        struct vhost_memory *memory;
+
         mutex_lock(&n->dev.mutex);
         err = vhost_dev_check_owner(&n->dev);
         if (err)
                 goto done;
+        memory = vhost_dev_reset_owner_prepare();
+        if (!memory) {
+                err = -ENOMEM;
+                goto done;
+        }
         vhost_test_stop(n, &priv);
         vhost_test_flush(n);
-        err = vhost_dev_reset_owner(&n->dev);
+        vhost_dev_reset_owner(&n->dev, memory);
 done:
         mutex_unlock(&n->dev.mutex);
         return err;
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 6dcd81c87432..749b5ab5bfbb 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -386,21 +386,19 @@ err_mm:
         return err;
 }
 
-/* Caller should have device mutex */
-long vhost_dev_reset_owner(struct vhost_dev *dev)
+struct vhost_memory *vhost_dev_reset_owner_prepare(void)
 {
-        struct vhost_memory *memory;
-
-        /* Restore memory to default empty mapping. */
-        memory = kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
-        if (!memory)
-                return -ENOMEM;
+        return kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
+}
 
+/* Caller should have device mutex */
+void vhost_dev_reset_owner(struct vhost_dev *dev, struct vhost_memory *memory)
+{
         vhost_dev_cleanup(dev, true);
 
+        /* Restore memory to default empty mapping. */
         memory->nregions = 0;
         RCU_INIT_POINTER(dev->memory, memory);
-        return 0;
 }
 
 void vhost_dev_stop(struct vhost_dev *dev)
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 1627eec0ca25..b58f4ae82cb8 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -136,7 +136,8 @@ struct vhost_dev {
 
 long vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue **vqs, int nvqs);
 long vhost_dev_check_owner(struct vhost_dev *);
-long vhost_dev_reset_owner(struct vhost_dev *);
+struct vhost_memory *vhost_dev_reset_owner_prepare(void);
+void vhost_dev_reset_owner(struct vhost_dev *, struct vhost_memory *);
 void vhost_dev_cleanup(struct vhost_dev *, bool locked);
 void vhost_dev_stop(struct vhost_dev *);
 long vhost_dev_ioctl(struct vhost_dev *, unsigned int ioctl, void __user *argp);