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

Dmitry Vyukov
2018-05-07T13:12:56Z

On Mon, May 7, 2018 at 3:03 PM, Michael S. Tsirkin <mst@redhat.com> wrote:
> On Fri, Apr 27, 2018 at 11:45:02AM -0400, Kevin Easton 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
>> ---
>> 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;
>
>
> Let's just init the msg though.
>
> OK it seems this is the best we can do for now,
> we need a new feature bit to fix it for 32 bit
> userspace on 64 bit kernels.
>
> Does the following help?

Hi Michael,

You can ask reporter (syzbot) to test:
https://github.com/google/syzkaller/blob/master/docs/syzbot.md#testing-patches
https://github.com/google/syzkaller/blob/master/docs/syzbot.md#kmsan-bugs

> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index f3bd8e9..58d9aec 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -2342,6 +2342,9 @@ 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);
> node->vq = vq;
> node->msg.type = type;
> return node;
>
> --
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