Re: [PATCH net] vhost: Use kzalloc() to allocate vhost_msg_node

Dmitry Vyukov
2018-04-27T16:25:43Z

On Fri, Apr 27, 2018 at 6:15 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
>> >> The struct vhost_msg within struct vhost_msg_node is copied to userspace,
>> >> so it should be allocated with kzalloc() to ensure all structure padding
>> >> is zeroed.
>> >>
>> >> Signed-off-by: Kevin Easton <kevin@guarana.org>
>> >> Reported-by: syzbot+87cfa083e727a224754b@syzkaller.appspotmail.com
>> >
>> > Does it help if a patch naming the padding is applied,
>> > and then we init just the relevant field?
>> > Just curious.
>>
>> Yes, it would help.
>
> I think it's slightly better that way then. node has a lot of internal
> stuff we don't care to init. Would you mind taking my patch and building
> on top of that then?

But it's asking for more information leaks in future. This looks like
work for compiler.

>> >> ---
>> >> drivers/vhost/vhost.c | 2 +-
>> >> 1 file changed, 1 insertion(+), 1 deletion(-)
>> >>
>> >> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>> >> index f3bd8e9..1b84dcff 100644
>> >> --- a/drivers/vhost/vhost.c
>> >> +++ b/drivers/vhost/vhost.c
>> >> @@ -2339,7 +2339,7 @@ EXPORT_SYMBOL_GPL(vhost_disable_notify);
>> >> /* Create a new message. */
>> >> struct vhost_msg_node *vhost_new_msg(struct vhost_virtqueue *vq, int type)
>> >> {
>> >> - struct vhost_msg_node *node = kmalloc(sizeof *node, GFP_KERNEL);
>> >> + struct vhost_msg_node *node = kzalloc(sizeof *node, GFP_KERNEL);
>> >> if (!node)
>> >> return NULL;
>> >> node->vq = vq;
>> >> --
>> >> 2.8.1