From: Willem de Bruijn <willemb@xxxxxxxxxx>
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 <willemb@xxxxxxxxxx>
Suggested-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
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