From: Willem de Bruijn <[email protected]> 3.12-stable review patch. If anyone has any objections, please let me know.
=============== [ Upstream commit 837585a5375c38d40361cfe64e6fd11e1addb936 ] 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 <[email protected]> Suggested-by: Eric Dumazet <[email protected]> Acked-by: Eric Dumazet <[email protected]> Signed-off-by: David S. Miller <[email protected]> Signed-off-by: Jiri Slaby <[email protected]> --- drivers/net/macvtap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c index 98ce4feb9a79..2f6da225fab4 100644 --- a/drivers/net/macvtap.c +++ b/drivers/net/macvtap.c @@ -655,7 +655,7 @@ 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) @@ -792,7 +792,7 @@ 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 ((len -= vnet_hdr_len) < 0) return -EINVAL; -- 2.12.0
