[PATCH 5.19 028/101] vduse: prevent uninitialized memory accesses

[Greg Kroah-Hartman]

From: Maxime Coquelin <maxime.coquelin@xxxxxxxxxx>

commit 46f8a29272e51b6df7393d58fc5cb8967397ef2b upstream.

If the VDUSE application provides a smaller config space
than the driver expects, the driver may use uninitialized
memory from the stack.

This patch prevents it by initializing the buffer passed by
the driver to store the config value.

This fix addresses CVE-2022-2308.

Cc: stable@xxxxxxxxxxxxxxx # v5.15+
Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace")
Reviewed-by: Xie Yongji <xieyongji@xxxxxxxxxxxxx>
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
Signed-off-by: Maxime Coquelin <maxime.coquelin@xxxxxxxxxx>
Message-Id: <20220831154923.97809-1-maxime.coquelin@xxxxxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Reviewed-by: Chaitanya Kulkarni <kch@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/vdpa/vdpa_user/vduse_dev.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -662,10 +662,15 @@ static void vduse_vdpa_get_config(struct
 {
 	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
 
-	if (offset > dev->config_size ||
-	    len > dev->config_size - offset)
+	/* Initialize the buffer in case of partial copy. */
+	memset(buf, 0, len);
+
+	if (offset > dev->config_size)
 		return;
 
+	if (len > dev->config_size - offset)
+		len = dev->config_size - offset;
+
 	memcpy(buf, dev->config + offset, len);
 }