linux-kernel - [PATCH for 5.10] vdpa_sim: fix param validation in vdpasim_get

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Date:   Thu, 11 Feb 2021 17:25:19 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     stable@...r.kernel.org
Cc:     Jason Wang <jasowang@...hat.com>,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org,
        Stefano Garzarella <sgarzare@...hat.com>,
        Eli Cohen <elic@...dia.com>,
        "Michael S. Tsirkin" <mst@...hat.com>
Subject: [PATCH for 5.10] vdpa_sim: fix param validation in vdpasim_get_config()

Commit 65b709586e222fa6ffd4166ac7fdb5d5dad113ee upstream.

Before this patch, if 'offset + len' was equal to
sizeof(struct virtio_net_config), the entire buffer wasn't filled,
returning incorrect values to the caller.

Since 'vdpasim->config' type is 'struct virtio_net_config', we can
safely copy its content under this condition.

Commit 65b709586e22 ("vdpa_sim: add get_config callback in
vdpasim_dev_attr") unintentionally solved it upstream while
refactoring vdpa_sim.c to support multiple devices. But we don't want
to backport it to stable branches as it contains many changes.

Fixes: 2c53d0f64c06 ("vdpasim: vDPA device simulator")
Cc: <stable@...r.kernel.org> # 5.10.x
Signed-off-by: Stefano Garzarella <sgarzare@...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 6a90fdb9cbfc..8ca178d7b02f 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
@@ -572,7 +572,7 @@ 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))
+	if (offset + len <= sizeof(struct virtio_net_config))
 		memcpy(buf, (u8 *)&vdpasim->config + offset, len);
 }
 
-- 
2.29.2