[PATCH 2/2 v4] vdpa: check that offsets are within bounds

From: Dan Carpenter <dan.carpenter@oracle.com>
To: "Michael S. Tsirkin" <mst@redhat.com>,
	Tiwei Bie <tiwei.bie@intel.com>,
	Xie Yongji <xieyongji@bytedance.com>
Cc: "Jason Wang" <jasowang@redhat.com>,
	"Eugenio Pérez" <eperezma@redhat.com>,
	kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
	kernel-janitors@vger.kernel.org
Subject: [PATCH 2/2 v4] vdpa: check that offsets are within bounds
Date: Wed, 8 Dec 2021 13:33:37 +0300	[thread overview]
Message-ID: <20211208103337.GA4047@kili> (raw)
In-Reply-To: <20211208103307.GA3778@kili>

In this function "c->off" is a u32 and "size" is a long.  On 64bit systems
if "c->off" is greater than "size" then "size - c->off" is a negative and
we always return -E2BIG.  But on 32bit systems the subtraction is type
promoted to a high positive u32 value and basically any "c->len" is
accepted.

Fixes: 4c8cf31885f6 ("vhost: introduce vDPA-based backend")
Reported-by: Xie Yongji <xieyongji@bytedance.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
v4: split into a separate patch

 drivers/vhost/vdpa.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 29cced1cd277..e3c4f059b21a 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -197,7 +197,7 @@ static int vhost_vdpa_config_validate(struct vhost_vdpa *v,
 	struct vdpa_device *vdpa = v->vdpa;
 	long size = vdpa->config->get_config_size(vdpa);
 
-	if (c->len == 0)
+	if (c->len == 0 || c->off > size)
 		return -EINVAL;
 
 	if (c->len > size - c->off)
-- 
2.20.1

