vhost: fix error handling in vring ioctls

Stanse found a locking problem in vhost_set_vring:
several returns from VHOST_SET_VRING_KICK, VHOST_SET_VRING_CALL,
VHOST_SET_VRING_ERR with the vq->mutex held.
Fix these up.

Reported-by: Jiri Slaby <jirislaby@gmail.com>
Acked-by: Laurent Chavey <chavey@google.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 12 insertions, 6 deletions

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 7cd55e078794..7bd7a1e4409d 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -476,8 +476,10 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
                 if (r < 0)
                         break;
                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
-                if (IS_ERR(eventfp))
-                        return PTR_ERR(eventfp);
+                if (IS_ERR(eventfp)) {
+                        r = PTR_ERR(eventfp);
+                        break;
+                }
                 if (eventfp != vq->kick) {
                         pollstop = filep = vq->kick;
                         pollstart = vq->kick = eventfp;
@@ -489,8 +491,10 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
                 if (r < 0)
                         break;
                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
-                if (IS_ERR(eventfp))
-                        return PTR_ERR(eventfp);
+                if (IS_ERR(eventfp)) {
+                        r = PTR_ERR(eventfp);
+                        break;
+                }
                 if (eventfp != vq->call) {
                         filep = vq->call;
                         ctx = vq->call_ctx;
@@ -505,8 +509,10 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
                 if (r < 0)
                         break;
                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
-                if (IS_ERR(eventfp))
-                        return PTR_ERR(eventfp);
+                if (IS_ERR(eventfp)) {
+                        r = PTR_ERR(eventfp);
+                        break;
+                }
                 if (eventfp != vq->error) {
                         filep = vq->error;
                         vq->error = eventfp;