linux-kernel - [PATCH 5.10 12/99] vdpa: check that offsets are within bounds

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Message-Id: <20211220143029.761728936@linuxfoundation.org>
Date:   Mon, 20 Dec 2021 15:33:45 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Xie Yongji <xieyongji@...edance.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        "Michael S. Tsirkin" <mst@...hat.com>
Subject: [PATCH 5.10 12/99] vdpa: check that offsets are within bounds

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

commit 3ed21c1451a14d139e1ceb18f2fa70865ce3195a upstream.

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@...edance.com>
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Link: https://lore.kernel.org/r/20211208103337.GA4047@kili
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
Cc: stable@...r.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/vhost/vdpa.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -196,7 +196,7 @@ static int vhost_vdpa_config_validate(st
 		break;
 	}
 
-	if (c->len == 0)
+	if (c->len == 0 || c->off > size)
 		return -EINVAL;
 
 	if (c->len > size - c->off)