Message ID | 20170203232049.38982-3-willemdebruijn.kernel@gmail.com |
---|---|
State | Accepted, archived |
Delegated to: | David Miller |
Headers | show |
On Fri, 2017-02-03 at 18:20 -0500, Willem de Bruijn wrote: > From: Willem de Bruijn <willemb@google.com> > > When IFF_VNET_HDR is enabled, a virtio_net header must precede data. > Data length is verified to be greater than or equal to expected header > length tun->vnet_hdr_sz before copying. > > Macvtap functions read the value once, but unless READ_ONCE is used, > the compiler may ignore this and read multiple times. Enforce a single > read and locally cached value to avoid updates between test and use. > > Signed-off-by: Willem de Bruijn <willemb@google.com> > Suggested-by: Eric Dumazet <edumazet@google.com> > --- Acked-by: Eric Dumazet <edumazet@google.com>
diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c index 402618565838..c27011bbe30c 100644 --- a/drivers/net/macvtap.c +++ b/drivers/net/macvtap.c @@ -681,7 +681,7 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m, size_t linear; if (q->flags & IFF_VNET_HDR) { - vnet_hdr_len = q->vnet_hdr_sz; + vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz); err = -EINVAL; if (len < vnet_hdr_len) @@ -820,7 +820,7 @@ static ssize_t macvtap_put_user(struct macvtap_queue *q, if (q->flags & IFF_VNET_HDR) { struct virtio_net_hdr vnet_hdr; - vnet_hdr_len = q->vnet_hdr_sz; + vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz); if (iov_iter_count(iter) < vnet_hdr_len) return -EINVAL;