4.17-stable review patch. If anyone has any objections, please let me know.
------------------
From: Michael S. Tsirkin mst@redhat.com
commit 670ae9caaca467ea1bfd325cb2a5c98ba87f94ad upstream.
struct vhost_msg within struct vhost_msg_node is copied to userspace. Unfortunately it turns out on 64 bit systems vhost_msg has padding after type which gcc doesn't initialize, leaking 4 uninitialized bytes to userspace.
This padding also unfortunately means 32 bit users of this interface are broken on a 64 bit kernel which will need to be fixed separately.
Fixes: CVE-2018-1118 Cc: stable@vger.kernel.org Reported-by: Kevin Easton kevin@guarana.org Signed-off-by: Michael S. Tsirkin mst@redhat.com Reported-by: syzbot+87cfa083e727a224754b@syzkaller.appspotmail.com Signed-off-by: Michael S. Tsirkin mst@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/vhost/vhost.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -2345,6 +2345,9 @@ struct vhost_msg_node *vhost_new_msg(str struct vhost_msg_node *node = kmalloc(sizeof *node, GFP_KERNEL); if (!node) return NULL; + + /* Make sure all padding within the structure is initialized. */ + memset(&node->msg, 0, sizeof node->msg); node->vq = vq; node->msg.type = type; return node;