linux-kernel - Re: [PATCH net] vhost: Use kzalloc() to allocate vhost_msg

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Date:   Fri, 27 Apr 2018 19:05:45 +0300
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Kevin Easton <kevin@...rana.org>
Cc:     Jason Wang <jasowang@...hat.com>, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH net] vhost: Use kzalloc() to allocate vhost_msg_node

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@...rana.org>
> Reported-by: syzbot+87cfa083e727a224754b@...kaller.appspotmail.com

Does it help if a patch naming the padding is applied,
and then we init just the relevant field?
Just curious.

> ---
>  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