Commit 0db25098 authored by Willem de Bruijn's avatar Willem de Bruijn Committed by Greg Kroah-Hartman

macvtap: read vnet_hdr_size once

[ Upstream commit 837585a5 ]

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: default avatarWillem de Bruijn <willemb@google.com>
Suggested-by: default avatarEric Dumazet <edumazet@google.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 625bd9e4
...@@ -725,7 +725,7 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m, ...@@ -725,7 +725,7 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
ssize_t n; ssize_t n;
if (q->flags & IFF_VNET_HDR) { if (q->flags & IFF_VNET_HDR) {
vnet_hdr_len = q->vnet_hdr_sz; vnet_hdr_len = READ_ONCE(q->vnet_hdr_sz);
err = -EINVAL; err = -EINVAL;
if (len < vnet_hdr_len) if (len < vnet_hdr_len)
...@@ -865,7 +865,7 @@ static ssize_t macvtap_put_user(struct macvtap_queue *q, ...@@ -865,7 +865,7 @@ static ssize_t macvtap_put_user(struct macvtap_queue *q,
if (q->flags & IFF_VNET_HDR) { if (q->flags & IFF_VNET_HDR) {
struct virtio_net_hdr 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) if (iov_iter_count(iter) < vnet_hdr_len)
return -EINVAL; return -EINVAL;
......
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