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>

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 7cd55e07879455abe95e04fa06656623b415c9a9..7bd7a1e4409d4e6f384c513734b743a1b56a55ca 100644 (file)
--- 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;