releases/5.9.5/vhost_vdpa-return-efault-if-copy_from_user-fails.patch

From 7922460e33c81f41e0d2421417228b32e6fdbe94 Mon Sep 17 00:00:00 2001
From: Dan Carpenter <dan.carpenter@oracle.com>
Date: Fri, 23 Oct 2020 15:08:53 +0300
Subject: vhost_vdpa: Return -EFAULT if copy_from_user() fails

From: Dan Carpenter <dan.carpenter@oracle.com>

commit 7922460e33c81f41e0d2421417228b32e6fdbe94 upstream.

The copy_to/from_user() functions return the number of bytes which we
weren't able to copy but the ioctl should return -EFAULT if they fail.

Fixes: a127c5bbb6a8 ("vhost-vdpa: fix backend feature ioctls")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20201023120853.GI282278@mwanda
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Cc: stable@vger.kernel.org
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/vhost/vdpa.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -428,12 +428,11 @@ static long vhost_vdpa_unlocked_ioctl(st
 	void __user *argp = (void __user *)arg;
 	u64 __user *featurep = argp;
 	u64 features;
-	long r;
+	long r = 0;
 
 	if (cmd == VHOST_SET_BACKEND_FEATURES) {
-		r = copy_from_user(&features, featurep, sizeof(features));
-		if (r)
-			return r;
+		if (copy_from_user(&features, featurep, sizeof(features)))
+			return -EFAULT;
 		if (features & ~VHOST_VDPA_BACKEND_FEATURES)
 			return -EOPNOTSUPP;
 		vhost_set_backend_features(&v->vdev, features);
@@ -476,7 +475,8 @@ static long vhost_vdpa_unlocked_ioctl(st
 		break;
 	case VHOST_GET_BACKEND_FEATURES:
 		features = VHOST_VDPA_BACKEND_FEATURES;
-		r = copy_to_user(featurep, &features, sizeof(features));
+		if (copy_to_user(featurep, &features, sizeof(features)))
+			r = -EFAULT;
 		break;
 	default:
 		r = vhost_dev_ioctl(&v->vdev, cmd, argp);