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authorWillem de Bruijn <willemb@google.com>2017-02-03 18:20:49 -0500
committerDavid S. Miller <davem@davemloft.net>2017-02-06 22:41:27 -0500
commit837585a5375c38d40361cfe64e6fd11e1addb936 (patch)
tree9acf1060c120551d70a9b31fc8075bf1d834eb98 /drivers/net/macvtap.c
parente1edab87faf6ca30cd137e0795bc73aa9a9a22ec (diff)
macvtap: read vnet_hdr_size once
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> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/macvtap.c')
-rw-r--r--drivers/net/macvtap.c4
1 files changed, 2 insertions, 2 deletions
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;