[PATCH 5.11 022/120] vhost-vdpa: set v->config_ctx to NULL if eventfd_ctx_fdget() fails

[Greg Kroah-Hartman]

From: Stefano Garzarella <sgarzare@xxxxxxxxxx>

commit 0bde59c1723a29e294765c96dbe5c7fb639c2f96 upstream.

In vhost_vdpa_set_config_call() if eventfd_ctx_fdget() fails the
'v->config_ctx' contains an error instead of a valid pointer.

Since we consider 'v->config_ctx' valid if it is not NULL, we should
set it to NULL in this case to avoid to use an invalid pointer in
other functions such as vhost_vdpa_config_put().

Fixes: 776f395004d8 ("vhost_vdpa: Support config interrupt in vdpa")
Cc: lingshan.zhu@xxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210311135257.109460-3-sgarzare@xxxxxxxxxx
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/vhost/vdpa.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -331,8 +331,12 @@ static long vhost_vdpa_set_config_call(s
 	if (!IS_ERR_OR_NULL(ctx))
 		eventfd_ctx_put(ctx);
 
-	if (IS_ERR(v->config_ctx))
-		return PTR_ERR(v->config_ctx);
+	if (IS_ERR(v->config_ctx)) {
+		long ret = PTR_ERR(v->config_ctx);
+
+		v->config_ctx = NULL;
+		return ret;
+	}
 
 	v->vdpa->config->set_config_cb(v->vdpa, &cb);