[PATCH 0/4] XSA-39 CVE-2013-021[67]: Linux netback DoS via malicious guest ring.

[PATCH 0/4] XSA-39 CVE-2013-021[67]: Linux netback DoS via malicious guest ring.

[Ian Campbell]

The Xen netback implementation contains a couple of flaws which can
allow a guest to cause a DoS in the backend domain, potentially
affecting other domains in the system.

CVE-2013-0216 is a failure to sanity check the ring producer/consumer
pointers which can allow a guest to cause netback to loop for an
extended period preventing other work from occurring.

CVE-2013-0217 is a memory leak on an error path which is guest
triggerable.

The following series contains the fixes for these issues, as previously
included in Xen Security Advisory 39:
http://lists.xen.org/archives/html/xen-announce/2013-02/msg00001.html

Ian.

[PATCH 1/4] xen/netback: shutdown the ring if it contains garbage.

[Ian Campbell]

A buggy or malicious frontend should not be able to confuse netback.
If we spot anything which is not as it should be then shutdown the
device and don't try to continue with the ring in a potentially
hostile state. Well behaved and non-hostile frontends will not be
penalised.

As well as making the existing checks for such errors fatal also add a
new check that ensures that there isn't an insane number of requests
on the ring (i.e. more than would fit in the ring). If the ring
contains garbage then previously is was possible to loop over this
insane number, getting an error each time and therefore not generating
any more pending requests and therefore not exiting the loop in
xen_netbk_tx_build_gops for an externded period.

Also turn various netdev_dbg calls which no precipitate a fatal error
into netdev_err, they are rate limited because the device is shutdown
afterwards.

This fixes at least one known DoS/softlockup of the backend domain.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Jan Beulich <JBeulich@suse.com>
---
 drivers/net/xen-netback/common.h    |    3 ++
 drivers/net/xen-netback/interface.c |   23 ++++++++-----
 drivers/net/xen-netback/netback.c   |   63 +++++++++++++++++++++++++---------
 3 files changed, 63 insertions(+), 26 deletions(-)

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 94b79c3..9d7f172 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -151,6 +151,9 @@ void xen_netbk_queue_tx_skb(struct xenvif *vif, struct sk_buff *skb);
 /* Notify xenvif that ring now has space to send an skb to the frontend */
 void xenvif_notify_tx_completion(struct xenvif *vif);
 
+/* Prevent the device from generating any further traffic. */
+void xenvif_carrier_off(struct xenvif *vif);
+
 /* Returns number of ring slots required to send an skb to the frontend */
 unsigned int xen_netbk_count_skb_slots(struct xenvif *vif, struct sk_buff *skb);
 
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index b7d41f8..b8c5193 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -343,17 +343,22 @@ err:
 	return err;
 }
 
-void xenvif_disconnect(struct xenvif *vif)
+void xenvif_carrier_off(struct xenvif *vif)
 {
 	struct net_device *dev = vif->dev;
-	if (netif_carrier_ok(dev)) {
-		rtnl_lock();
-		netif_carrier_off(dev); /* discard queued packets */
-		if (netif_running(dev))
-			xenvif_down(vif);
-		rtnl_unlock();
-		xenvif_put(vif);
-	}
+
+	rtnl_lock();
+	netif_carrier_off(dev); /* discard queued packets */
+	if (netif_running(dev))
+		xenvif_down(vif);
+	rtnl_unlock();
+	xenvif_put(vif);
+}
+
+void xenvif_disconnect(struct xenvif *vif)
+{
+	if (netif_carrier_ok(vif->dev))
+		xenvif_carrier_off(vif);
 
 	atomic_dec(&vif->refcnt);
 	wait_event(vif->waiting_to_free, atomic_read(&vif->refcnt) == 0);
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index f2d6b78..1a449f9 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -888,6 +888,13 @@ static void netbk_tx_err(struct xenvif *vif,
 	xenvif_put(vif);
 }
 
+static void netbk_fatal_tx_err(struct xenvif *vif)
+{
+	netdev_err(vif->dev, "fatal error; disabling device\n");
+	xenvif_carrier_off(vif);
+	xenvif_put(vif);
+}
+
 static int netbk_count_requests(struct xenvif *vif,
 				struct xen_netif_tx_request *first,
 				struct xen_netif_tx_request *txp,
@@ -901,19 +908,22 @@ static int netbk_count_requests(struct xenvif *vif,
 
 	do {
 		if (frags >= work_to_do) {
-			netdev_dbg(vif->dev, "Need more frags\n");
+			netdev_err(vif->dev, "Need more frags\n");
+			netbk_fatal_tx_err(vif);
 			return -frags;
 		}
 
 		if (unlikely(frags >= MAX_SKB_FRAGS)) {
-			netdev_dbg(vif->dev, "Too many frags\n");
+			netdev_err(vif->dev, "Too many frags\n");
+			netbk_fatal_tx_err(vif);
 			return -frags;
 		}
 
 		memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + frags),
 		       sizeof(*txp));
 		if (txp->size > first->size) {
-			netdev_dbg(vif->dev, "Frags galore\n");
+			netdev_err(vif->dev, "Frag is bigger than frame.\n");
+			netbk_fatal_tx_err(vif);
 			return -frags;
 		}
 
@@ -921,8 +931,9 @@ static int netbk_count_requests(struct xenvif *vif,
 		frags++;
 
 		if (unlikely((txp->offset + txp->size) > PAGE_SIZE)) {
-			netdev_dbg(vif->dev, "txp->offset: %x, size: %u\n",
+			netdev_err(vif->dev, "txp->offset: %x, size: %u\n",
 				 txp->offset, txp->size);
+			netbk_fatal_tx_err(vif);
 			return -frags;
 		}
 	} while ((txp++)->flags & XEN_NETTXF_more_data);
@@ -1095,7 +1106,8 @@ static int xen_netbk_get_extras(struct xenvif *vif,
 
 	do {
 		if (unlikely(work_to_do-- <= 0)) {
-			netdev_dbg(vif->dev, "Missing extra info\n");
+			netdev_err(vif->dev, "Missing extra info\n");
+			netbk_fatal_tx_err(vif);
 			return -EBADR;
 		}
 
@@ -1104,8 +1116,9 @@ static int xen_netbk_get_extras(struct xenvif *vif,
 		if (unlikely(!extra.type ||
 			     extra.type >= XEN_NETIF_EXTRA_TYPE_MAX)) {
 			vif->tx.req_cons = ++cons;
-			netdev_dbg(vif->dev,
+			netdev_err(vif->dev,
 				   "Invalid extra type: %d\n", extra.type);
+			netbk_fatal_tx_err(vif);
 			return -EINVAL;
 		}
 
@@ -1121,13 +1134,15 @@ static int netbk_set_skb_gso(struct xenvif *vif,
 			     struct xen_netif_extra_info *gso)
 {
 	if (!gso->u.gso.size) {
-		netdev_dbg(vif->dev, "GSO size must not be zero.\n");
+		netdev_err(vif->dev, "GSO size must not be zero.\n");
+		netbk_fatal_tx_err(vif);
 		return -EINVAL;
 	}
 
 	/* Currently only TCPv4 S.O. is supported. */
 	if (gso->u.gso.type != XEN_NETIF_GSO_TYPE_TCPV4) {
-		netdev_dbg(vif->dev, "Bad GSO type %d.\n", gso->u.gso.type);
+		netdev_err(vif->dev, "Bad GSO type %d.\n", gso->u.gso.type);
+		netbk_fatal_tx_err(vif);
 		return -EINVAL;
 	}
 
@@ -1264,9 +1279,26 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 
 		/* Get a netif from the list with work to do. */
 		vif = poll_net_schedule_list(netbk);
+		/*
+		 * This can sometimes happen because the test of
+		 * list_empty(net_schedule_list) at the top of the
+		 * loop is unlocked.  Just go back and have another
+		 * look.
+		 */
 		if (!vif)
 			continue;
 
+		if (vif->tx.sring->req_prod - vif->tx.req_cons >
+		    XEN_NETIF_TX_RING_SIZE) {
+			netdev_err(vif->dev,
+				   "Impossible number of requests. "
+				   "req_prod %d, req_cons %d, size %ld\n",
+				   vif->tx.sring->req_prod, vif->tx.req_cons,
+				   XEN_NETIF_TX_RING_SIZE);
+			netbk_fatal_tx_err(vif);
+			continue;
+		}
+
 		RING_FINAL_CHECK_FOR_REQUESTS(&vif->tx, work_to_do);
 		if (!work_to_do) {
 			xenvif_put(vif);
@@ -1294,17 +1326,14 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 			work_to_do = xen_netbk_get_extras(vif, extras,
 							  work_to_do);
 			idx = vif->tx.req_cons;
-			if (unlikely(work_to_do < 0)) {
-				netbk_tx_err(vif, &txreq, idx);
+			if (unlikely(work_to_do < 0))
 				continue;
-			}
 		}
 
 		ret = netbk_count_requests(vif, &txreq, txfrags, work_to_do);
-		if (unlikely(ret < 0)) {
-			netbk_tx_err(vif, &txreq, idx - ret);
+		if (unlikely(ret < 0))
 			continue;
-		}
+
 		idx += ret;
 
 		if (unlikely(txreq.size < ETH_HLEN)) {
@@ -1316,11 +1345,11 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 
 		/* No crossing a page as the payload mustn't fragment. */
 		if (unlikely((txreq.offset + txreq.size) > PAGE_SIZE)) {
-			netdev_dbg(vif->dev,
+			netdev_err(vif->dev,
 				   "txreq.offset: %x, size: %u, end: %lu\n",
 				   txreq.offset, txreq.size,
 				   (txreq.offset&~PAGE_MASK) + txreq.size);
-			netbk_tx_err(vif, &txreq, idx);
+			netbk_fatal_tx_err(vif);
 			continue;
 		}
 
@@ -1348,8 +1377,8 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 			gso = &extras[XEN_NETIF_EXTRA_TYPE_GSO - 1];
 
 			if (netbk_set_skb_gso(vif, skb, gso)) {
+				/* Failure in netbk_set_skb_gso is fatal. */
 				kfree_skb(skb);
-				netbk_tx_err(vif, &txreq, idx);
 				continue;
 			}
 		}
-- 
1.7.2.5

[PATCH 1/4] xen/netback: shutdown the ring if it contains garbage.

[Ian Campbell]

A buggy or malicious frontend should not be able to confuse netback.
If we spot anything which is not as it should be then shutdown the
device and don't try to continue with the ring in a potentially
hostile state. Well behaved and non-hostile frontends will not be
penalised.

As well as making the existing checks for such errors fatal also add a
new check that ensures that there isn't an insane number of requests
on the ring (i.e. more than would fit in the ring). If the ring
contains garbage then previously is was possible to loop over this
insane number, getting an error each time and therefore not generating
any more pending requests and therefore not exiting the loop in
xen_netbk_tx_build_gops for an externded period.

Also turn various netdev_dbg calls which no precipitate a fatal error
into netdev_err, they are rate limited because the device is shutdown
afterwards.

This fixes at least one known DoS/softlockup of the backend domain.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Jan Beulich <JBeulich@suse.com>
---
 drivers/net/xen-netback/common.h    |    3 ++
 drivers/net/xen-netback/interface.c |   23 ++++++++-----
 drivers/net/xen-netback/netback.c   |   63 +++++++++++++++++++++++++---------
 3 files changed, 63 insertions(+), 26 deletions(-)

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 94b79c3..9d7f172 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -151,6 +151,9 @@ void xen_netbk_queue_tx_skb(struct xenvif *vif, struct sk_buff *skb);
 /* Notify xenvif that ring now has space to send an skb to the frontend */
 void xenvif_notify_tx_completion(struct xenvif *vif);
 
+/* Prevent the device from generating any further traffic. */
+void xenvif_carrier_off(struct xenvif *vif);
+
 /* Returns number of ring slots required to send an skb to the frontend */
 unsigned int xen_netbk_count_skb_slots(struct xenvif *vif, struct sk_buff *skb);
 
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index b7d41f8..b8c5193 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -343,17 +343,22 @@ err:
 	return err;
 }
 
-void xenvif_disconnect(struct xenvif *vif)
+void xenvif_carrier_off(struct xenvif *vif)
 {
 	struct net_device *dev = vif->dev;
-	if (netif_carrier_ok(dev)) {
-		rtnl_lock();
-		netif_carrier_off(dev); /* discard queued packets */
-		if (netif_running(dev))
-			xenvif_down(vif);
-		rtnl_unlock();
-		xenvif_put(vif);
-	}
+
+	rtnl_lock();
+	netif_carrier_off(dev); /* discard queued packets */
+	if (netif_running(dev))
+		xenvif_down(vif);
+	rtnl_unlock();
+	xenvif_put(vif);
+}
+
+void xenvif_disconnect(struct xenvif *vif)
+{
+	if (netif_carrier_ok(vif->dev))
+		xenvif_carrier_off(vif);
 
 	atomic_dec(&vif->refcnt);
 	wait_event(vif->waiting_to_free, atomic_read(&vif->refcnt) == 0);
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index f2d6b78..1a449f9 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -888,6 +888,13 @@ static void netbk_tx_err(struct xenvif *vif,
 	xenvif_put(vif);
 }
 
+static void netbk_fatal_tx_err(struct xenvif *vif)
+{
+	netdev_err(vif->dev, "fatal error; disabling device\n");
+	xenvif_carrier_off(vif);
+	xenvif_put(vif);
+}
+
 static int netbk_count_requests(struct xenvif *vif,
 				struct xen_netif_tx_request *first,
 				struct xen_netif_tx_request *txp,
@@ -901,19 +908,22 @@ static int netbk_count_requests(struct xenvif *vif,
 
 	do {
 		if (frags >= work_to_do) {
-			netdev_dbg(vif->dev, "Need more frags\n");
+			netdev_err(vif->dev, "Need more frags\n");
+			netbk_fatal_tx_err(vif);
 			return -frags;
 		}
 
 		if (unlikely(frags >= MAX_SKB_FRAGS)) {
-			netdev_dbg(vif->dev, "Too many frags\n");
+			netdev_err(vif->dev, "Too many frags\n");
+			netbk_fatal_tx_err(vif);
 			return -frags;
 		}
 
 		memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + frags),
 		       sizeof(*txp));
 		if (txp->size > first->size) {
-			netdev_dbg(vif->dev, "Frags galore\n");
+			netdev_err(vif->dev, "Frag is bigger than frame.\n");
+			netbk_fatal_tx_err(vif);
 			return -frags;
 		}
 
@@ -921,8 +931,9 @@ static int netbk_count_requests(struct xenvif *vif,
 		frags++;
 
 		if (unlikely((txp->offset + txp->size) > PAGE_SIZE)) {
-			netdev_dbg(vif->dev, "txp->offset: %x, size: %u\n",
+			netdev_err(vif->dev, "txp->offset: %x, size: %u\n",
 				 txp->offset, txp->size);
+			netbk_fatal_tx_err(vif);
 			return -frags;
 		}
 	} while ((txp++)->flags & XEN_NETTXF_more_data);
@@ -1095,7 +1106,8 @@ static int xen_netbk_get_extras(struct xenvif *vif,
 
 	do {
 		if (unlikely(work_to_do-- <= 0)) {
-			netdev_dbg(vif->dev, "Missing extra info\n");
+			netdev_err(vif->dev, "Missing extra info\n");
+			netbk_fatal_tx_err(vif);
 			return -EBADR;
 		}
 
@@ -1104,8 +1116,9 @@ static int xen_netbk_get_extras(struct xenvif *vif,
 		if (unlikely(!extra.type ||
 			     extra.type >= XEN_NETIF_EXTRA_TYPE_MAX)) {
 			vif->tx.req_cons = ++cons;
-			netdev_dbg(vif->dev,
+			netdev_err(vif->dev,
 				   "Invalid extra type: %d\n", extra.type);
+			netbk_fatal_tx_err(vif);
 			return -EINVAL;
 		}
 
@@ -1121,13 +1134,15 @@ static int netbk_set_skb_gso(struct xenvif *vif,
 			     struct xen_netif_extra_info *gso)
 {
 	if (!gso->u.gso.size) {
-		netdev_dbg(vif->dev, "GSO size must not be zero.\n");
+		netdev_err(vif->dev, "GSO size must not be zero.\n");
+		netbk_fatal_tx_err(vif);
 		return -EINVAL;
 	}
 
 	/* Currently only TCPv4 S.O. is supported. */
 	if (gso->u.gso.type != XEN_NETIF_GSO_TYPE_TCPV4) {
-		netdev_dbg(vif->dev, "Bad GSO type %d.\n", gso->u.gso.type);
+		netdev_err(vif->dev, "Bad GSO type %d.\n", gso->u.gso.type);
+		netbk_fatal_tx_err(vif);
 		return -EINVAL;
 	}
 
@@ -1264,9 +1279,26 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 
 		/* Get a netif from the list with work to do. */
 		vif = poll_net_schedule_list(netbk);
+		/*
+		 * This can sometimes happen because the test of
+		 * list_empty(net_schedule_list) at the top of the
+		 * loop is unlocked.  Just go back and have another
+		 * look.
+		 */
 		if (!vif)
 			continue;
 
+		if (vif->tx.sring->req_prod - vif->tx.req_cons >
+		    XEN_NETIF_TX_RING_SIZE) {
+			netdev_err(vif->dev,
+				   "Impossible number of requests. "
+				   "req_prod %d, req_cons %d, size %ld\n",
+				   vif->tx.sring->req_prod, vif->tx.req_cons,
+				   XEN_NETIF_TX_RING_SIZE);
+			netbk_fatal_tx_err(vif);
+			continue;
+		}
+
 		RING_FINAL_CHECK_FOR_REQUESTS(&vif->tx, work_to_do);
 		if (!work_to_do) {
 			xenvif_put(vif);
@@ -1294,17 +1326,14 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 			work_to_do = xen_netbk_get_extras(vif, extras,
 							  work_to_do);
 			idx = vif->tx.req_cons;
-			if (unlikely(work_to_do < 0)) {
-				netbk_tx_err(vif, &txreq, idx);
+			if (unlikely(work_to_do < 0))
 				continue;
-			}
 		}
 
 		ret = netbk_count_requests(vif, &txreq, txfrags, work_to_do);
-		if (unlikely(ret < 0)) {
-			netbk_tx_err(vif, &txreq, idx - ret);
+		if (unlikely(ret < 0))
 			continue;
-		}
+
 		idx += ret;
 
 		if (unlikely(txreq.size < ETH_HLEN)) {
@@ -1316,11 +1345,11 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 
 		/* No crossing a page as the payload mustn't fragment. */
 		if (unlikely((txreq.offset + txreq.size) > PAGE_SIZE)) {
-			netdev_dbg(vif->dev,
+			netdev_err(vif->dev,
 				   "txreq.offset: %x, size: %u, end: %lu\n",
 				   txreq.offset, txreq.size,
 				   (txreq.offset&~PAGE_MASK) + txreq.size);
-			netbk_tx_err(vif, &txreq, idx);
+			netbk_fatal_tx_err(vif);
 			continue;
 		}
 
@@ -1348,8 +1377,8 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 			gso = &extras[XEN_NETIF_EXTRA_TYPE_GSO - 1];
 
 			if (netbk_set_skb_gso(vif, skb, gso)) {
+				/* Failure in netbk_set_skb_gso is fatal. */
 				kfree_skb(skb);
-				netbk_tx_err(vif, &txreq, idx);
 				continue;
 			}
 		}
-- 
1.7.2.5

[PATCH 2/4] xen/netback: don't leak pages on failure in xen_netbk_tx_check_gop.

[Ian Campbell]

From: Matthew Daley <mattjd@gmail.com>

Signed-off-by: Matthew Daley <mattjd@gmail.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Jan Beulich <JBeulich@suse.com>
---
 drivers/net/xen-netback/netback.c |   38 ++++++++++++------------------------
 1 files changed, 13 insertions(+), 25 deletions(-)

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 1a449f9..975241e 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -147,7 +147,8 @@ void xen_netbk_remove_xenvif(struct xenvif *vif)
 	atomic_dec(&netbk->netfront_count);
 }
 
-static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx);
+static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx,
+				  u8 status);
 static void make_tx_response(struct xenvif *vif,
 			     struct xen_netif_tx_request *txp,
 			     s8       st);
@@ -1007,30 +1008,20 @@ static int xen_netbk_tx_check_gop(struct xen_netbk *netbk,
 {
 	struct gnttab_copy *gop = *gopp;
 	u16 pending_idx = *((u16 *)skb->data);
-	struct pending_tx_info *pending_tx_info = netbk->pending_tx_info;
-	struct xenvif *vif = pending_tx_info[pending_idx].vif;
-	struct xen_netif_tx_request *txp;
 	struct skb_shared_info *shinfo = skb_shinfo(skb);
 	int nr_frags = shinfo->nr_frags;
 	int i, err, start;
 
 	/* Check status of header. */
 	err = gop->status;
-	if (unlikely(err)) {
-		pending_ring_idx_t index;
-		index = pending_index(netbk->pending_prod++);
-		txp = &pending_tx_info[pending_idx].req;
-		make_tx_response(vif, txp, XEN_NETIF_RSP_ERROR);
-		netbk->pending_ring[index] = pending_idx;
-		xenvif_put(vif);
-	}
+	if (unlikely(err))
+		xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_ERROR);
 
 	/* Skip first skb fragment if it is on same page as header fragment. */
 	start = (frag_get_pending_idx(&shinfo->frags[0]) == pending_idx);
 
 	for (i = start; i < nr_frags; i++) {
 		int j, newerr;
-		pending_ring_idx_t index;
 
 		pending_idx = frag_get_pending_idx(&shinfo->frags[i]);
 
@@ -1039,16 +1030,12 @@ static int xen_netbk_tx_check_gop(struct xen_netbk *netbk,
 		if (likely(!newerr)) {
 			/* Had a previous error? Invalidate this fragment. */
 			if (unlikely(err))
-				xen_netbk_idx_release(netbk, pending_idx);
+				xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY);
 			continue;
 		}
 
 		/* Error on this fragment: respond to client with an error. */
-		txp = &netbk->pending_tx_info[pending_idx].req;
-		make_tx_response(vif, txp, XEN_NETIF_RSP_ERROR);
-		index = pending_index(netbk->pending_prod++);
-		netbk->pending_ring[index] = pending_idx;
-		xenvif_put(vif);
+		xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_ERROR);
 
 		/* Not the first error? Preceding frags already invalidated. */
 		if (err)
@@ -1056,10 +1043,10 @@ static int xen_netbk_tx_check_gop(struct xen_netbk *netbk,
 
 		/* First error: invalidate header and preceding fragments. */
 		pending_idx = *((u16 *)skb->data);
-		xen_netbk_idx_release(netbk, pending_idx);
+		xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY);
 		for (j = start; j < i; j++) {
 			pending_idx = frag_get_pending_idx(&shinfo->frags[j]);
-			xen_netbk_idx_release(netbk, pending_idx);
+			xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY);
 		}
 
 		/* Remember the error: invalidate all subsequent fragments. */
@@ -1093,7 +1080,7 @@ static void xen_netbk_fill_frags(struct xen_netbk *netbk, struct sk_buff *skb)
 
 		/* Take an extra reference to offset xen_netbk_idx_release */
 		get_page(netbk->mmap_pages[pending_idx]);
-		xen_netbk_idx_release(netbk, pending_idx);
+		xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY);
 	}
 }
 
@@ -1477,7 +1464,7 @@ static void xen_netbk_tx_submit(struct xen_netbk *netbk)
 			txp->size -= data_len;
 		} else {
 			/* Schedule a response immediately. */
-			xen_netbk_idx_release(netbk, pending_idx);
+			xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY);
 		}
 
 		if (txp->flags & XEN_NETTXF_csum_blank)
@@ -1529,7 +1516,8 @@ static void xen_netbk_tx_action(struct xen_netbk *netbk)
 	xen_netbk_tx_submit(netbk);
 }
 
-static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx)
+static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx,
+				  u8 status)
 {
 	struct xenvif *vif;
 	struct pending_tx_info *pending_tx_info;
@@ -1543,7 +1531,7 @@ static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx)
 
 	vif = pending_tx_info->vif;
 
-	make_tx_response(vif, &pending_tx_info->req, XEN_NETIF_RSP_OKAY);
+	make_tx_response(vif, &pending_tx_info->req, status);
 
 	index = pending_index(netbk->pending_prod++);
 	netbk->pending_ring[index] = pending_idx;
-- 
1.7.2.5

[PATCH 2/4] xen/netback: don't leak pages on failure in xen_netbk_tx_check_gop.

[Ian Campbell]

From: Matthew Daley <mattjd@gmail.com>

Signed-off-by: Matthew Daley <mattjd@gmail.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Jan Beulich <JBeulich@suse.com>
---
 drivers/net/xen-netback/netback.c |   38 ++++++++++++------------------------
 1 files changed, 13 insertions(+), 25 deletions(-)

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 1a449f9..975241e 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -147,7 +147,8 @@ void xen_netbk_remove_xenvif(struct xenvif *vif)
 	atomic_dec(&netbk->netfront_count);
 }
 
-static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx);
+static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx,
+				  u8 status);
 static void make_tx_response(struct xenvif *vif,
 			     struct xen_netif_tx_request *txp,
 			     s8       st);
@@ -1007,30 +1008,20 @@ static int xen_netbk_tx_check_gop(struct xen_netbk *netbk,
 {
 	struct gnttab_copy *gop = *gopp;
 	u16 pending_idx = *((u16 *)skb->data);
-	struct pending_tx_info *pending_tx_info = netbk->pending_tx_info;
-	struct xenvif *vif = pending_tx_info[pending_idx].vif;
-	struct xen_netif_tx_request *txp;
 	struct skb_shared_info *shinfo = skb_shinfo(skb);
 	int nr_frags = shinfo->nr_frags;
 	int i, err, start;
 
 	/* Check status of header. */
 	err = gop->status;
-	if (unlikely(err)) {
-		pending_ring_idx_t index;
-		index = pending_index(netbk->pending_prod++);
-		txp = &pending_tx_info[pending_idx].req;
-		make_tx_response(vif, txp, XEN_NETIF_RSP_ERROR);
-		netbk->pending_ring[index] = pending_idx;
-		xenvif_put(vif);
-	}
+	if (unlikely(err))
+		xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_ERROR);
 
 	/* Skip first skb fragment if it is on same page as header fragment. */
 	start = (frag_get_pending_idx(&shinfo->frags[0]) == pending_idx);
 
 	for (i = start; i < nr_frags; i++) {
 		int j, newerr;
-		pending_ring_idx_t index;
 
 		pending_idx = frag_get_pending_idx(&shinfo->frags[i]);
 
@@ -1039,16 +1030,12 @@ static int xen_netbk_tx_check_gop(struct xen_netbk *netbk,
 		if (likely(!newerr)) {
 			/* Had a previous error? Invalidate this fragment. */
 			if (unlikely(err))
-				xen_netbk_idx_release(netbk, pending_idx);
+				xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY);
 			continue;
 		}
 
 		/* Error on this fragment: respond to client with an error. */
-		txp = &netbk->pending_tx_info[pending_idx].req;
-		make_tx_response(vif, txp, XEN_NETIF_RSP_ERROR);
-		index = pending_index(netbk->pending_prod++);
-		netbk->pending_ring[index] = pending_idx;
-		xenvif_put(vif);
+		xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_ERROR);
 
 		/* Not the first error? Preceding frags already invalidated. */
 		if (err)
@@ -1056,10 +1043,10 @@ static int xen_netbk_tx_check_gop(struct xen_netbk *netbk,
 
 		/* First error: invalidate header and preceding fragments. */
 		pending_idx = *((u16 *)skb->data);
-		xen_netbk_idx_release(netbk, pending_idx);
+		xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY);
 		for (j = start; j < i; j++) {
 			pending_idx = frag_get_pending_idx(&shinfo->frags[j]);
-			xen_netbk_idx_release(netbk, pending_idx);
+			xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY);
 		}
 
 		/* Remember the error: invalidate all subsequent fragments. */
@@ -1093,7 +1080,7 @@ static void xen_netbk_fill_frags(struct xen_netbk *netbk, struct sk_buff *skb)
 
 		/* Take an extra reference to offset xen_netbk_idx_release */
 		get_page(netbk->mmap_pages[pending_idx]);
-		xen_netbk_idx_release(netbk, pending_idx);
+		xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY);
 	}
 }
 
@@ -1477,7 +1464,7 @@ static void xen_netbk_tx_submit(struct xen_netbk *netbk)
 			txp->size -= data_len;
 		} else {
 			/* Schedule a response immediately. */
-			xen_netbk_idx_release(netbk, pending_idx);
+			xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_OKAY);
 		}
 
 		if (txp->flags & XEN_NETTXF_csum_blank)
@@ -1529,7 +1516,8 @@ static void xen_netbk_tx_action(struct xen_netbk *netbk)
 	xen_netbk_tx_submit(netbk);
 }
 
-static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx)
+static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx,
+				  u8 status)
 {
 	struct xenvif *vif;
 	struct pending_tx_info *pending_tx_info;
@@ -1543,7 +1531,7 @@ static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx)
 
 	vif = pending_tx_info->vif;
 
-	make_tx_response(vif, &pending_tx_info->req, XEN_NETIF_RSP_OKAY);
+	make_tx_response(vif, &pending_tx_info->req, status);
 
 	index = pending_index(netbk->pending_prod++);
 	netbk->pending_ring[index] = pending_idx;
-- 
1.7.2.5

[PATCH 3/4] xen/netback: free already allocated memory on failure in xen_netbk_get_requests

[Ian Campbell]

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
---
 drivers/net/xen-netback/netback.c |   16 +++++++++++++++-
 1 files changed, 15 insertions(+), 1 deletions(-)

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 975241e..1a99288 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -978,7 +978,7 @@ static struct gnttab_copy *xen_netbk_get_requests(struct xen_netbk *netbk,
 		pending_idx = netbk->pending_ring[index];
 		page = xen_netbk_alloc_page(netbk, skb, pending_idx);
 		if (!page)
-			return NULL;
+			goto err;
 
 		gop->source.u.ref = txp->gref;
 		gop->source.domid = vif->domid;
@@ -1000,6 +1000,20 @@ static struct gnttab_copy *xen_netbk_get_requests(struct xen_netbk *netbk,
 	}
 
 	return gop;
+err:
+	/*
+	 * Unwind, freeing all pages and sending error
+	 * reponses.
+	 */
+	while (i-- > start) {
+		xen_netbk_idx_release(netbk, frag_get_pending_idx(&frags[i]),
+				      XEN_NETIF_RSP_ERROR);
+	}
+	/* The head too, if necessary. */
+	if (start)
+		xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_ERROR);
+
+	return NULL;
 }
 
 static int xen_netbk_tx_check_gop(struct xen_netbk *netbk,
-- 
1.7.2.5

[PATCH 3/4] xen/netback: free already allocated memory on failure in xen_netbk_get_requests

[Ian Campbell]

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
---
 drivers/net/xen-netback/netback.c |   16 +++++++++++++++-
 1 files changed, 15 insertions(+), 1 deletions(-)

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 975241e..1a99288 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -978,7 +978,7 @@ static struct gnttab_copy *xen_netbk_get_requests(struct xen_netbk *netbk,
 		pending_idx = netbk->pending_ring[index];
 		page = xen_netbk_alloc_page(netbk, skb, pending_idx);
 		if (!page)
-			return NULL;
+			goto err;
 
 		gop->source.u.ref = txp->gref;
 		gop->source.domid = vif->domid;
@@ -1000,6 +1000,20 @@ static struct gnttab_copy *xen_netbk_get_requests(struct xen_netbk *netbk,
 	}
 
 	return gop;
+err:
+	/*
+	 * Unwind, freeing all pages and sending error
+	 * reponses.
+	 */
+	while (i-- > start) {
+		xen_netbk_idx_release(netbk, frag_get_pending_idx(&frags[i]),
+				      XEN_NETIF_RSP_ERROR);
+	}
+	/* The head too, if necessary. */
+	if (start)
+		xen_netbk_idx_release(netbk, pending_idx, XEN_NETIF_RSP_ERROR);
+
+	return NULL;
 }
 
 static int xen_netbk_tx_check_gop(struct xen_netbk *netbk,
-- 
1.7.2.5

[PATCH 4/4] netback: correct netbk_tx_err to handle wrap around.

[Ian Campbell]

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Jan Beulich <JBeulich@suse.com>
---
 drivers/net/xen-netback/netback.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 1a99288..28d5e06 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -880,7 +880,7 @@ static void netbk_tx_err(struct xenvif *vif,
 
 	do {
 		make_tx_response(vif, txp, XEN_NETIF_RSP_ERROR);
-		if (cons >= end)
+		if (cons == end)
 			break;
 		txp = RING_GET_REQUEST(&vif->tx, cons++);
 	} while (1);
-- 
1.7.2.5

[PATCH 4/4] netback: correct netbk_tx_err to handle wrap around.

[Ian Campbell]

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Jan Beulich <JBeulich@suse.com>
---
 drivers/net/xen-netback/netback.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 1a99288..28d5e06 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -880,7 +880,7 @@ static void netbk_tx_err(struct xenvif *vif,
 
 	do {
 		make_tx_response(vif, txp, XEN_NETIF_RSP_ERROR);
-		if (cons >= end)
+		if (cons == end)
 			break;
 		txp = RING_GET_REQUEST(&vif->tx, cons++);
 	} while (1);
-- 
1.7.2.5

Re: [PATCH 3/4] xen/netback: free already allocated memory on failure in xen_netbk_get_requests

[Ben Pfaff]

Ian Campbell <ian.campbell@citrix.com> writes:

> +	/*
> +	 * Unwind, freeing all pages and sending error
> +	 * reponses.
> +	 */

s/reponses/responses/

Re: [PATCH 3/4] xen/netback: free already allocated memory on failure in xen_netbk_get_requests

[Ben Pfaff]

Ian Campbell <ian.campbell@citrix.com> writes:

> +	/*
> +	 * Unwind, freeing all pages and sending error
> +	 * reponses.
> +	 */

s/reponses/responses/

Re: [PATCH 3/4] xen/netback: free already allocated memory on failure in xen_netbk_get_requests

[David Miller]

From: Ben Pfaff <blp@cs.stanford.edu>
Date: Wed, 06 Feb 2013 09:31:24 -0800

> Ian Campbell <ian.campbell@citrix.com> writes:
> 
>> +	/*
>> +	 * Unwind, freeing all pages and sending error
>> +	 * reponses.
>> +	 */
> 
> s/reponses/responses/

Also please format your comments in the standard networking form
which is:

	/* Like
	 * this.
	 */

Patch #1 has the same problem, thanks Ian.

Re: [PATCH 3/4] xen/netback: free already allocated memory on failure in xen_netbk_get_requests

[David Miller]

From: Ben Pfaff <blp@cs.stanford.edu>
Date: Wed, 06 Feb 2013 09:31:24 -0800

> Ian Campbell <ian.campbell@citrix.com> writes:
> 
>> +	/*
>> +	 * Unwind, freeing all pages and sending error
>> +	 * reponses.
>> +	 */
> 
> s/reponses/responses/

Also please format your comments in the standard networking form
which is:

	/* Like
	 * this.
	 */

Patch #1 has the same problem, thanks Ian.

Re: [PATCH 3/4] xen/netback: free already allocated memory on failure in xen_netbk_get_requests

[Ian Campbell]

On Wed, 2013-02-06 at 18:47 +0000, David Miller wrote:
> From: Ben Pfaff <blp@cs.stanford.edu>
> Date: Wed, 06 Feb 2013 09:31:24 -0800
> 
> > Ian Campbell <ian.campbell@citrix.com> writes:
> > 
> >> +	/*
> >> +	 * Unwind, freeing all pages and sending error
> >> +	 * reponses.
> >> +	 */
> > 
> > s/reponses/responses/

Fixed, thanks!

> Also please format your comments in the standard networking form
> which is:
> 
> 	/* Like
> 	 * this.
> 	 */
> 
> Patch #1 has the same problem, thanks Ian.

I fixed this up, actually this particular one fits on a single line just
fine.

I'll resend shortly with the addition of the stable cc which I forgot
last time.

Thanks,
Ian.

Re: [PATCH 3/4] xen/netback: free already allocated memory on failure in xen_netbk_get_requests

[Ian Campbell]

On Wed, 2013-02-06 at 18:47 +0000, David Miller wrote:
> From: Ben Pfaff <blp@cs.stanford.edu>
> Date: Wed, 06 Feb 2013 09:31:24 -0800
> 
> > Ian Campbell <ian.campbell@citrix.com> writes:
> > 
> >> +	/*
> >> +	 * Unwind, freeing all pages and sending error
> >> +	 * reponses.
> >> +	 */
> > 
> > s/reponses/responses/

Fixed, thanks!

> Also please format your comments in the standard networking form
> which is:
> 
> 	/* Like
> 	 * this.
> 	 */
> 
> Patch #1 has the same problem, thanks Ian.

I fixed this up, actually this particular one fits on a single line just
fine.

I'll resend shortly with the addition of the stable cc which I forgot
last time.

Thanks,
Ian.

[PATCH 0/4] XSA-39 CVE-2013-021[67]: Linux netback DoS via malicious guest ring.

[Ian Campbell]

The Xen netback implementation contains a couple of flaws which can
allow a guest to cause a DoS in the backend domain, potentially
affecting other domains in the system.

CVE-2013-0216 is a failure to sanity check the ring producer/consumer
pointers which can allow a guest to cause netback to loop for an
extended period preventing other work from occurring.

CVE-2013-0217 is a memory leak on an error path which is guest
triggerable.

The following series contains the fixes for these issues, as previously
included in Xen Security Advisory 39:
http://lists.xen.org/archives/html/xen-announce/2013-02/msg00001.html

Ian.