kernel/net-vhost-fix-total-length-when-packets-are-too-short.patch

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Bugzilla: 1081504
Upstream-status: Sent to netdev list
From patchwork Thu Mar 27 10:00:26 2014
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: [PATCHv2,net] vhost: fix total length when packets are too short
From: "Michael S. Tsirkin" <mst@redhat.com>
X-Patchwork-Id: 334283
Message-Id: <20140327100026.GA30715@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: kvm@vger.kernel.org, virtio-dev@lists.oasis-open.org,
virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
Jason Wang <jasowang@redhat.com>, David Miller <davem@davemloft.net>
Date: Thu, 27 Mar 2014 12:00:26 +0200
When mergeable buffers are disabled, and the
incoming packet is too large for the rx buffer,
get_rx_bufs returns success.
This was intentional in order for make recvmsg
truncate the packet and then handle_rx would
detect err != sock_len and drop it.
Unfortunately we pass the original sock_len to
recvmsg - which means we use parts of iov not fully
validated.
Fix this up by detecting this overrun and doing packet drop
immediately.
CVE-2014-0077
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
Changes from v1:
Fix CVE# in the commit log.
Patch is unchanged.
Note: this is needed for -stable.
I wonder if this can still make the release.
drivers/vhost/net.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index a0fa5de..026be58 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -532,6 +532,12 @@ static int get_rx_bufs(struct vhost_virtqueue *vq,
*iovcount = seg;
if (unlikely(log))
*log_num = nlogs;
+
+ /* Detect overrun */
+ if (unlikely(datalen > 0)) {
+ r = UIO_MAXIOV + 1;
+ goto err;
+ }
return headcount;
err:
vhost_discard_vq_desc(vq, headcount);
@@ -587,6 +593,14 @@ static void handle_rx(struct vhost_net *net)
/* On error, stop handling until the next kick. */
if (unlikely(headcount < 0))
break;
+ /* On overrun, truncate and discard */
+ if (unlikely(headcount > UIO_MAXIOV)) {
+ msg.msg_iovlen = 1;
+ err = sock->ops->recvmsg(NULL, sock, &msg,
+ 1, MSG_DONTWAIT | MSG_TRUNC);
+ pr_debug("Discarded rx packet: len %zd\n", sock_len);
+ continue;
+ }
/* OK, now we need to know about added descriptors. */
if (!headcount) {
if (unlikely(vhost_enable_notify(&net->dev, vq))) {