From: Maxime Coquelin <maxime.coquelin@redhat.com>
Date: Wed, 31 Aug 2022 17:49:23 +0200
Subject: [PATCH] vduse: prevent uninitialized memory accesses
Message-Id: <20220831154923.97809-1-maxime.coquelin@redhat.com>
Patch-mainline: Submitted, virtualization ML
References: CVE-2022-2308 bsc#1202573

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@vger.kernel.org # v5.15+
Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace")
Reviewed-by: Xie Yongji <xieyongji@bytedance.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

---
 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
@@ -673,10 +673,15 @@
 {
 	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);
 }