linux-kernel - [PATCH] vdpa_sim: fix pointer math in get

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Date:   Mon, 10 Aug 2020 08:58:35 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        Jason Wang <jasowang@...hat.com>,
        virtualization@...ts.linux-foundation.org
Subject: [PATCH] vdpa_sim: fix pointer math in get_config

There is a pointer math bug here: the variable cast is a struct so the
offset is in units of struct size.  If "offset" is non-zero this will
copy memory from beyond the end of the array.

fixes: 2c53d0f64c06 ("vdpasim: vDPA device simulator")
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---
 drivers/vdpa/vdpa_sim/vdpa_sim.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
index 604d9d25ca47..62d640327145 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
@@ -558,7 +558,7 @@ static void vdpasim_get_config(struct vdpa_device *vdpa, unsigned int offset,
 	struct vdpasim *vdpasim = vdpa_to_sim(vdpa);
 
 	if (offset + len < sizeof(struct virtio_net_config))
-		memcpy(buf, &vdpasim->config + offset, len);
+		memcpy(buf, (u8 *)&vdpasim->config + offset, len);
 }
 
 static void vdpasim_set_config(struct vdpa_device *vdpa, unsigned int offset,
-- 
MST