On Thu, Jun 07, 2018 at 08:59:06PM +0300, Michael S. Tsirkin wrote: > On Thu, Jun 07, 2018 at 06:43:55PM +0100, Al Viro wrote: > > On Thu, Jun 07, 2018 at 06:38:48PM +0300, Michael S. Tsirkin wrote: > > > #syz test: https://github.com/google/kmsan.git/master d2d741e5d1898dfde1a75ea3d29a9a3e2edf0617 > > > > > > Subject: vhost: fix info leak > > > > > > Fixes: CVE-2018-1118 > > > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> > > > --- > > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > > > index f0be5f35ab28..9beefa6ed1ce 100644 > > > --- a/drivers/vhost/vhost.c > > > +++ b/drivers/vhost/vhost.c > > > @@ -2345,6 +2345,9 @@ struct vhost_msg_node *vhost_new_msg(struct vhost_virtqueue *vq, int type) > > > 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); > > > > Umm... Maybe kzalloc(), then? You have > > > > struct vhost_msg_node { > > struct vhost_msg msg; > > struct vhost_virtqueue *vq; > > struct list_head node; > > }; > > > > and that's what, 68 bytes in msg, then either 4 bytes pointer or > > 4 bytes padding + 8 bytes pointer, then two pointers? How much > > does explicit partial memset() save you here? > > Yes but 0 isn't a nop here so if this struct is used without > a sensible initialization, it will crash elsewhere. > I prefer KASAN to catch such uses. > > > > > node->vq = vq; > > > node->msg.type = type; IDGI - what would your variant catch that kzalloc + 2 assignments won't? Accesses to uninitialized ->node? Because that's the only difference in what is and is not initialized between those variants...
