[PATCH V4 0/7] Bundle fixes for Xen netfront / netback

[PATCH V4 0/7] Bundle fixes for Xen netfront / netback

[Wei Liu]

1-3 have been applied to DaveM's tree, repost for completeness.

4 is an incremental patch on top of 2.

5 now accounts for MAX_TCP_HEADER instead of vlan ethernet header.

6 now only touches TX path, RX path still has MAX_SKB_FRAGS dependency.

7 is modified to adapt to 6.


Wei.

[PATCH V4 1/7] xen-netfront: remove unused variable `extra'

[Wei Liu]

This variable is supposed to hold reference to the last extra_info in the
loop. However there is only type of extra info here and the loop to process
extra info is missing, so this variable is never used and causes confusion.

Remove it at the moment. We can add it back when necessary.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
---
 drivers/net/xen-netfront.c |    8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 7ffa43b..5527663 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -537,7 +537,6 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	struct netfront_info *np = netdev_priv(dev);
 	struct netfront_stats *stats = this_cpu_ptr(np->stats);
 	struct xen_netif_tx_request *tx;
-	struct xen_netif_extra_info *extra;
 	char *data = skb->data;
 	RING_IDX i;
 	grant_ref_t ref;
@@ -581,7 +580,6 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	tx->gref = np->grant_tx_ref[id] = ref;
 	tx->offset = offset;
 	tx->size = len;
-	extra = NULL;
 
 	tx->flags = 0;
 	if (skb->ip_summed == CHECKSUM_PARTIAL)
@@ -597,10 +595,7 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		gso = (struct xen_netif_extra_info *)
 			RING_GET_REQUEST(&np->tx, ++i);
 
-		if (extra)
-			extra->flags |= XEN_NETIF_EXTRA_FLAG_MORE;
-		else
-			tx->flags |= XEN_NETTXF_extra_info;
+		tx->flags |= XEN_NETTXF_extra_info;
 
 		gso->u.gso.size = skb_shinfo(skb)->gso_size;
 		gso->u.gso.type = XEN_NETIF_GSO_TYPE_TCPV4;
@@ -609,7 +604,6 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
 
 		gso->type = XEN_NETIF_EXTRA_TYPE_GSO;
 		gso->flags = 0;
-		extra = gso;
 	}
 
 	np->tx.req_prod_pvt = i + 1;
-- 
1.7.10.4

[PATCH V4 2/7] xen-netfront: frags -> slots in xennet_get_responses

[Wei Liu]

This function is in fact counting the ring slots required for responses.
Separate the concepts of ring slots and skb frags make the code clearer, as
now netfront and netback can have different MAX_SKB_FRAGS, slot and frag are
not mapped 1:1 any more.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
---
 drivers/net/xen-netfront.c |   18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 5527663..d9097a7 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -712,7 +712,7 @@ static int xennet_get_responses(struct netfront_info *np,
 	struct sk_buff *skb = xennet_get_rx_skb(np, cons);
 	grant_ref_t ref = xennet_get_rx_ref(np, cons);
 	int max = MAX_SKB_FRAGS + (rx->status <= RX_COPY_THRESHOLD);
-	int frags = 1;
+	int slots = 1;
 	int err = 0;
 	unsigned long ret;
 
@@ -756,27 +756,27 @@ next:
 		if (!(rx->flags & XEN_NETRXF_more_data))
 			break;
 
-		if (cons + frags == rp) {
+		if (cons + slots == rp) {
 			if (net_ratelimit())
-				dev_warn(dev, "Need more frags\n");
+				dev_warn(dev, "Need more slots\n");
 			err = -ENOENT;
 			break;
 		}
 
-		rx = RING_GET_RESPONSE(&np->rx, cons + frags);
-		skb = xennet_get_rx_skb(np, cons + frags);
-		ref = xennet_get_rx_ref(np, cons + frags);
-		frags++;
+		rx = RING_GET_RESPONSE(&np->rx, cons + slots);
+		skb = xennet_get_rx_skb(np, cons + slots);
+		ref = xennet_get_rx_ref(np, cons + slots);
+		slots++;
 	}
 
-	if (unlikely(frags > max)) {
+	if (unlikely(slots > max)) {
 		if (net_ratelimit())
 			dev_warn(dev, "Too many frags\n");
 		err = -E2BIG;
 	}
 
 	if (unlikely(err))
-		np->rx.rsp_cons = cons + frags;
+		np->rx.rsp_cons = cons + slots;
 
 	return err;
 }
-- 
1.7.10.4

[PATCH V4 3/7] xen-netback: remove skb in xen_netbk_alloc_page

[Wei Liu]

This variable is never used.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
---
 drivers/net/xen-netback/netback.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index da726a3..6e8e51a 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -948,7 +948,6 @@ static int netbk_count_requests(struct xenvif *vif,
 }
 
 static struct page *xen_netbk_alloc_page(struct xen_netbk *netbk,
-					 struct sk_buff *skb,
 					 u16 pending_idx)
 {
 	struct page *page;
@@ -982,7 +981,7 @@ static struct gnttab_copy *xen_netbk_get_requests(struct xen_netbk *netbk,
 
 		index = pending_index(netbk->pending_cons++);
 		pending_idx = netbk->pending_ring[index];
-		page = xen_netbk_alloc_page(netbk, skb, pending_idx);
+		page = xen_netbk_alloc_page(netbk, pending_idx);
 		if (!page)
 			goto err;
 
@@ -1387,7 +1386,7 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 		}
 
 		/* XXX could copy straight to head */
-		page = xen_netbk_alloc_page(netbk, skb, pending_idx);
+		page = xen_netbk_alloc_page(netbk, pending_idx);
 		if (!page) {
 			kfree_skb(skb);
 			netbk_tx_err(vif, &txreq, idx);
-- 
1.7.10.4

[PATCH V4 4/7] xen-netfront: frags -> slots in log message

[Wei Liu]

Also fix a typo in comment.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
---
 drivers/net/xen-netfront.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index d9097a7..1bb2e20 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -735,7 +735,7 @@ static int xennet_get_responses(struct netfront_info *np,
 		/*
 		 * This definitely indicates a bug, either in this driver or in
 		 * the backend driver. In future this should flag the bad
-		 * situation to the system controller to reboot the backed.
+		 * situation to the system controller to reboot the backend.
 		 */
 		if (ref == GRANT_INVALID_REF) {
 			if (net_ratelimit())
@@ -771,7 +771,7 @@ next:
 
 	if (unlikely(slots > max)) {
 		if (net_ratelimit())
-			dev_warn(dev, "Too many frags\n");
+			dev_warn(dev, "Too many slots\n");
 		err = -E2BIG;
 	}
 
-- 
1.7.10.4

Re: [PATCH V4 4/7] xen-netfront: frags -> slots in log message

[Ian Campbell]

On Fri, 2013-04-12 at 15:24 +0100, Wei Liu wrote:
> Also fix a typo in comment.
> 
> Signed-off-by: Wei Liu <wei.liu2@citrix.com>

Acked-by: Ian Campbell <ian.campbell@citrix.com>

[PATCH V4 5/7] xen-netfront: reduce gso_max_size to account for max TCP header

[Wei Liu]

The maximum packet including header that can be handled by netfront / netback
wire format is 65535. Reduce gso_max_size accordingly.

Drop skb and print warning when skb->len > 65535. This can 1) save the effort
to send malformed packet to netback, 2) help spotting misconfiguration of
netfront in the future.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
---
 drivers/net/xen-netfront.c |   14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 1bb2e20..9c2eca1 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -547,6 +547,16 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	unsigned int len = skb_headlen(skb);
 	unsigned long flags;
 
+	/* If skb->len is too big for wire format, drop skb and alert
+	 * user about misconfiguration.
+	 */
+	if (unlikely(skb->len > (typeof(tx->size))(~0))) {
+		net_alert_ratelimited(
+			"xennet: skb->len = %u, too big for wire format\n",
+			skb->len);
+		goto drop;
+	}
+
 	slots = DIV_ROUND_UP(offset + len, PAGE_SIZE) +
 		xennet_count_skb_frag_slots(skb);
 	if (unlikely(slots > MAX_SKB_FRAGS + 1)) {
@@ -1058,7 +1068,7 @@ err:
 
 static int xennet_change_mtu(struct net_device *dev, int mtu)
 {
-	int max = xennet_can_sg(dev) ? 65535 - ETH_HLEN : ETH_DATA_LEN;
+	int max = xennet_can_sg(dev) ? 65535 - MAX_TCP_HEADER : ETH_DATA_LEN;
 
 	if (mtu > max)
 		return -EINVAL;
@@ -1362,6 +1372,8 @@ static struct net_device *xennet_create_dev(struct xenbus_device *dev)
 	SET_ETHTOOL_OPS(netdev, &xennet_ethtool_ops);
 	SET_NETDEV_DEV(netdev, &dev->dev);
 
+	netif_set_gso_max_size(netdev, 65535 - MAX_TCP_HEADER);
+
 	np->netdev = netdev;
 
 	netif_carrier_off(netdev);
-- 
1.7.10.4

Re: [PATCH V4 5/7] xen-netfront: reduce gso_max_size to account for max TCP header

[Ian Campbell]

On Fri, 2013-04-12 at 15:24 +0100, Wei Liu wrote:
> The maximum packet including header that can be handled by netfront / netback
> wire format is 65535. Reduce gso_max_size accordingly.
> 
> Drop skb and print warning when skb->len > 65535. This can 1) save the effort
> to send malformed packet to netback, 2) help spotting misconfiguration of
> netfront in the future.
> 
> Signed-off-by: Wei Liu <wei.liu2@citrix.com>
> ---
>  drivers/net/xen-netfront.c |   14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
> index 1bb2e20..9c2eca1 100644
> --- a/drivers/net/xen-netfront.c
> +++ b/drivers/net/xen-netfront.c
> @@ -547,6 +547,16 @@ static int xennet_start_xmit(struct sk_buff *skb, struct net_device *dev)
>  	unsigned int len = skb_headlen(skb);
>  	unsigned long flags;
>  
> +	/* If skb->len is too big for wire format, drop skb and alert
> +	 * user about misconfiguration.
> +	 */
> +	if (unlikely(skb->len > (typeof(tx->size))(~0))) {

This seems rather a complicated way of saying... er, something!

Perhaps we could have a #define in netif.h to compare against?

I'm not 100% convinced that the case and the ~ are in the right order to
have the behaviour you want unless perhaps sizeof(tx->size) <
sizeof(int). In any case it's too obfuscated for me ;-)

> +		net_alert_ratelimited(
> +			"xennet: skb->len = %u, too big for wire format\n",
> +			skb->len);
> +		goto drop;
> +	}
> +
>  	slots = DIV_ROUND_UP(offset + len, PAGE_SIZE) +
>  		xennet_count_skb_frag_slots(skb);
>  	if (unlikely(slots > MAX_SKB_FRAGS + 1)) {
> @@ -1058,7 +1068,7 @@ err:
>  
>  static int xennet_change_mtu(struct net_device *dev, int mtu)
>  {
> -	int max = xennet_can_sg(dev) ? 65535 - ETH_HLEN : ETH_DATA_LEN;
> +	int max = xennet_can_sg(dev) ? 65535 - MAX_TCP_HEADER : ETH_DATA_LEN;
>  
>  	if (mtu > max)
>  		return -EINVAL;
> @@ -1362,6 +1372,8 @@ static struct net_device *xennet_create_dev(struct xenbus_device *dev)
>  	SET_ETHTOOL_OPS(netdev, &xennet_ethtool_ops);
>  	SET_NETDEV_DEV(netdev, &dev->dev);
>  
> +	netif_set_gso_max_size(netdev, 65535 - MAX_TCP_HEADER);
> +
>  	np->netdev = netdev;
>  
>  	netif_carrier_off(netdev);

Re: [PATCH V4 5/7] xen-netfront: reduce gso_max_size to account for max TCP header

[Jan Beulich]

>>> On 12.04.13 at 16:44, Ian Campbell <Ian.Campbell@citrix.com> wrote:
> On Fri, 2013-04-12 at 15:24 +0100, Wei Liu wrote:
>> The maximum packet including header that can be handled by netfront / 
> netback
>> wire format is 65535. Reduce gso_max_size accordingly.
>> 
>> Drop skb and print warning when skb->len > 65535. This can 1) save the effort
>> to send malformed packet to netback, 2) help spotting misconfiguration of
>> netfront in the future.
>> 
>> Signed-off-by: Wei Liu <wei.liu2@citrix.com>
>> ---
>>  drivers/net/xen-netfront.c |   14 +++++++++++++-
>>  1 file changed, 13 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
>> index 1bb2e20..9c2eca1 100644
>> --- a/drivers/net/xen-netfront.c
>> +++ b/drivers/net/xen-netfront.c
>> @@ -547,6 +547,16 @@ static int xennet_start_xmit(struct sk_buff *skb, 
> struct net_device *dev)
>>  	unsigned int len = skb_headlen(skb);
>>  	unsigned long flags;
>>  
>> +	/* If skb->len is too big for wire format, drop skb and alert
>> +	 * user about misconfiguration.
>> +	 */
>> +	if (unlikely(skb->len > (typeof(tx->size))(~0))) {
> 
> This seems rather a complicated way of saying... er, something!
> 
> Perhaps we could have a #define in netif.h to compare against?
> 
> I'm not 100% convinced that the case and the ~ are in the right order to
> have the behaviour you want unless perhaps sizeof(tx->size) <
> sizeof(int). In any case it's too obfuscated for me ;-)

Previously this was (u16)~0, which I complained to have no
correlation to where the restriction actually comes from. Hence
the request to use typeof() on the very field that doesn't
permit a larger value.

Jan

[PATCH V4 6/7] xen-netback: coalesce slots in TX path and fix regressions

[Wei Liu]

This patch tries to coalesce tx requests when constructing grant copy
structures. It enables netback to deal with situation when frontend's
MAX_SKB_FRAGS is larger than backend's MAX_SKB_FRAGS.

With the help of coalescing, this patch tries to address two regressions and
avoid reopening the security hole in XSA-39.

Regression 1. The reduction of the number of supported ring entries (slots)
per packet (from 18 to 17). This regression has been around for some time but
remains unnoticed until XSA-39 security fix. This is fixed by coalescing
slots.

Regression 2. The XSA-39 security fix turning "too many frags" errors from
just dropping the packet to a fatal error and disabling the VIF. This is fixed
by coalescing slots (handling 18 slots when backend's MAX_SKB_FRAGS is 17)
which rules out false positive (using 18 slots is legit) and dropping packets
using 19 to `max_skb_slots` slots.

To avoid reopening security hole in XSA-39, frontend sending packet using more
than max_skb_slots is considered malicious.

The behavior of netback for packet is thus:

    1-18            slots: valid
   19-max_skb_slots slots: drop and respond with an error
   max_skb_slots+   slots: fatal error

max_skb_slots is configurable by admin, default value is 20.

Also change variable name from "frags" to "slots" in netbk_count_requests.

Please note that RX path still has dependency on MAX_SKB_FRAGS. This will be
fixed with separate patch.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
---
 drivers/net/xen-netback/netback.c |  277 ++++++++++++++++++++++++++++++-------
 include/xen/interface/io/netif.h  |   18 +++
 2 files changed, 246 insertions(+), 49 deletions(-)

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 6e8e51a..00ae841 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -47,11 +47,47 @@
 #include <asm/xen/hypercall.h>
 #include <asm/xen/page.h>
 
+/*
+ * This is the maximum slots a skb can have. If a guest sends a skb
+ * which exceeds this limit it is considered malicious.
+ */
+#define MAX_SKB_SLOTS_DEFAULT 20
+static unsigned int max_skb_slots = MAX_SKB_SLOTS_DEFAULT;
+
+static int max_skb_slots_set(const char *val, const struct kernel_param *kp)
+{
+	int ret;
+	unsigned int param = 0;
+
+	ret = kstrtouint(val, 10, &param);
+
+	if (ret < 0 || param < XEN_NETIF_NR_SLOTS_MIN)
+		return -EINVAL;
+
+	max_skb_slots = param;
+
+	return 0;
+}
+
+static __moduleparam_const struct kernel_param_ops max_skb_slots_param_ops = {
+	.set = max_skb_slots_set,
+	.get = param_get_uint,
+};
+
+module_param_cb(max_skb_slots, &max_skb_slots_param_ops,
+		&max_skb_slots, 0444);
+
+typedef unsigned int pending_ring_idx_t;
+#define INVALID_PENDING_RING_IDX (~0U)
+
 struct pending_tx_info {
-	struct xen_netif_tx_request req;
+	struct xen_netif_tx_request req; /* coalesced tx request  */
 	struct xenvif *vif;
+	pending_ring_idx_t head; /* head != INVALID_PENDING_RING_IDX
+				  * if it is head of one or more tx
+				  * reqs
+				  */
 };
-typedef unsigned int pending_ring_idx_t;
 
 struct netbk_rx_meta {
 	int id;
@@ -102,7 +138,11 @@ struct xen_netbk {
 	atomic_t netfront_count;
 
 	struct pending_tx_info pending_tx_info[MAX_PENDING_REQS];
-	struct gnttab_copy tx_copy_ops[MAX_PENDING_REQS];
+	/* Coalescing tx requests before copying makes number of grant
+	 * copy ops greater of equal to number of slots required. In
+	 * worst case a tx request consumes 2 gnttab_copy.
+	 */
+	struct gnttab_copy tx_copy_ops[2*MAX_PENDING_REQS];
 
 	u16 pending_ring[MAX_PENDING_REQS];
 
@@ -250,6 +290,7 @@ static int max_required_rx_slots(struct xenvif *vif)
 {
 	int max = DIV_ROUND_UP(vif->dev->mtu, PAGE_SIZE);
 
+	/* XXX FIXME: RX path dependent on MAX_SKB_FRAGS */
 	if (vif->can_sg || vif->gso || vif->gso_prefix)
 		max += MAX_SKB_FRAGS + 1; /* extra_info + frags */
 
@@ -657,6 +698,7 @@ static void xen_netbk_rx_action(struct xen_netbk *netbk)
 		__skb_queue_tail(&rxq, skb);
 
 		/* Filled the batch queue? */
+		/* XXX FIXME: RX path dependent on MAX_SKB_FRAGS */
 		if (count + MAX_SKB_FRAGS >= XEN_NETIF_RX_RING_SIZE)
 			break;
 	}
@@ -904,47 +946,78 @@ static void netbk_fatal_tx_err(struct xenvif *vif)
 
 static int netbk_count_requests(struct xenvif *vif,
 				struct xen_netif_tx_request *first,
+				RING_IDX first_idx,
 				struct xen_netif_tx_request *txp,
 				int work_to_do)
 {
 	RING_IDX cons = vif->tx.req_cons;
-	int frags = 0;
+	int slots = 0;
+	int drop_err = 0;
 
 	if (!(first->flags & XEN_NETTXF_more_data))
 		return 0;
 
 	do {
-		if (frags >= work_to_do) {
-			netdev_err(vif->dev, "Need more frags\n");
+		if (slots >= work_to_do) {
+			netdev_err(vif->dev,
+				   "Asked for %d slots but exceeds this limit\n",
+				   work_to_do);
 			netbk_fatal_tx_err(vif);
 			return -ENODATA;
 		}
 
-		if (unlikely(frags >= MAX_SKB_FRAGS)) {
-			netdev_err(vif->dev, "Too many frags\n");
+		/* This guest is really using too many slots and
+		 * considered malicious.
+		 */
+		if (unlikely(slots >= max_skb_slots)) {
+			netdev_err(vif->dev,
+				   "Malicious frontend using %d slots, threshold %u\n",
+				   slots, max_skb_slots);
 			netbk_fatal_tx_err(vif);
 			return -E2BIG;
 		}
 
-		memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + frags),
+		/* Xen network protocol had implicit dependency on
+		 * MAX_SKB_FRAGS. XEN_NETIF_NR_SLOTS_MIN is set to the
+		 * historical MAX_SKB_FRAGS value 18 to honor the same
+		 * behavior as before. Any packet using more than 18
+		 * slots but less than max_skb_slots slots is dropped
+		 */
+		if (!drop_err && slots >= XEN_NETIF_NR_SLOTS_MIN) {
+			if (net_ratelimit())
+				netdev_dbg(vif->dev,
+					   "Too many slots (%d), dropping packet\n",
+					   slots);
+			drop_err = -E2BIG;
+		}
+
+		memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + slots),
 		       sizeof(*txp));
 		if (txp->size > first->size) {
-			netdev_err(vif->dev, "Frag is bigger than frame.\n");
+			netdev_err(vif->dev,
+				   "Invalid tx request, slot size %u > remaining size %u\n",
+				   txp->size, first->size);
 			netbk_fatal_tx_err(vif);
 			return -EIO;
 		}
 
 		first->size -= txp->size;
-		frags++;
+		slots++;
 
 		if (unlikely((txp->offset + txp->size) > PAGE_SIZE)) {
-			netdev_err(vif->dev, "txp->offset: %x, size: %u\n",
+			netdev_err(vif->dev, "Cross page boundary, txp->offset: %x, size: %u\n",
 				 txp->offset, txp->size);
 			netbk_fatal_tx_err(vif);
 			return -EINVAL;
 		}
 	} while ((txp++)->flags & XEN_NETTXF_more_data);
-	return frags;
+
+	if (drop_err) {
+		netbk_tx_err(vif, first, first_idx + slots);
+		return drop_err;
+	}
+
+	return slots;
 }
 
 static struct page *xen_netbk_alloc_page(struct xen_netbk *netbk,
@@ -968,48 +1041,114 @@ static struct gnttab_copy *xen_netbk_get_requests(struct xen_netbk *netbk,
 	struct skb_shared_info *shinfo = skb_shinfo(skb);
 	skb_frag_t *frags = shinfo->frags;
 	u16 pending_idx = *((u16 *)skb->data);
-	int i, start;
+	u16 head_idx = 0;
+	int slot, start;
+	struct page *page;
+	pending_ring_idx_t index, start_idx = 0;
+	uint16_t dst_offset;
+	unsigned int nr_slots;
+	struct pending_tx_info *first = NULL;
+
+	/* At this point shinfo->nr_frags is in fact the number of
+	 * slots, which can be as large as XEN_NETIF_NR_SLOTS_MIN.
+	 */
+	nr_slots = shinfo->nr_frags;
 
 	/* 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 < shinfo->nr_frags; i++, txp++) {
-		struct page *page;
-		pending_ring_idx_t index;
+	/* Coalesce tx requests, at this point the packet passed in
+	 * should be <= 64K. Any packets larger than 64K have been
+	 * handled in netbk_count_requests().
+	 */
+	for (shinfo->nr_frags = slot = start; slot < nr_slots;
+	     shinfo->nr_frags++) {
 		struct pending_tx_info *pending_tx_info =
 			netbk->pending_tx_info;
 
-		index = pending_index(netbk->pending_cons++);
-		pending_idx = netbk->pending_ring[index];
-		page = xen_netbk_alloc_page(netbk, pending_idx);
+		page = alloc_page(GFP_KERNEL|__GFP_COLD);
 		if (!page)
 			goto err;
 
-		gop->source.u.ref = txp->gref;
-		gop->source.domid = vif->domid;
-		gop->source.offset = txp->offset;
-
-		gop->dest.u.gmfn = virt_to_mfn(page_address(page));
-		gop->dest.domid = DOMID_SELF;
-		gop->dest.offset = txp->offset;
-
-		gop->len = txp->size;
-		gop->flags = GNTCOPY_source_gref;
+		dst_offset = 0;
+		first = NULL;
+		while (dst_offset < PAGE_SIZE && slot < nr_slots) {
+			gop->flags = GNTCOPY_source_gref;
+
+			gop->source.u.ref = txp->gref;
+			gop->source.domid = vif->domid;
+			gop->source.offset = txp->offset;
+
+			gop->dest.domid = DOMID_SELF;
+
+			gop->dest.offset = dst_offset;
+			gop->dest.u.gmfn = virt_to_mfn(page_address(page));
+
+			if (dst_offset + txp->size > PAGE_SIZE) {
+				/* This page can only merge a portion
+				 * of tx request. Do not increment any
+				 * pointer / counter here. The txp
+				 * will be dealt with in future
+				 * rounds, eventually hitting the
+				 * `else` branch.
+				 */
+				gop->len = PAGE_SIZE - dst_offset;
+				txp->offset += gop->len;
+				txp->size -= gop->len;
+				dst_offset += gop->len; /* quit loop */
+			} else {
+				/* This tx request can be merged in the page */
+				gop->len = txp->size;
+				dst_offset += gop->len;
+
+				index = pending_index(netbk->pending_cons++);
+
+				pending_idx = netbk->pending_ring[index];
+
+				memcpy(&pending_tx_info[pending_idx].req, txp,
+				       sizeof(*txp));
+				xenvif_get(vif);
+
+				pending_tx_info[pending_idx].vif = vif;
+
+				/* Poison these fields, corresponding
+				 * fields for head tx req will be set
+				 * to correct values after the loop.
+				 */
+				netbk->mmap_pages[pending_idx] = (void *)(~0UL);
+				pending_tx_info[pending_idx].head =
+					INVALID_PENDING_RING_IDX;
+
+				if (!first) {
+					first = &pending_tx_info[pending_idx];
+					start_idx = index;
+					head_idx = pending_idx;
+				}
+
+				txp++;
+				slot++;
+			}
 
-		gop++;
+			gop++;
+		}
 
-		memcpy(&pending_tx_info[pending_idx].req, txp, sizeof(*txp));
-		xenvif_get(vif);
-		pending_tx_info[pending_idx].vif = vif;
-		frag_set_pending_idx(&frags[i], pending_idx);
+		first->req.offset = 0;
+		first->req.size = dst_offset;
+		first->head = start_idx;
+		set_page_ext(page, netbk, head_idx);
+		netbk->mmap_pages[head_idx] = page;
+		frag_set_pending_idx(&frags[shinfo->nr_frags], head_idx);
 	}
 
+	BUG_ON(shinfo->nr_frags > MAX_SKB_FRAGS);
+
 	return gop;
 err:
 	/* Unwind, freeing all pages and sending error responses. */
-	while (i-- > start) {
-		xen_netbk_idx_release(netbk, frag_get_pending_idx(&frags[i]),
-				      XEN_NETIF_RSP_ERROR);
+	while (shinfo->nr_frags-- > start) {
+		xen_netbk_idx_release(netbk,
+				frag_get_pending_idx(&frags[shinfo->nr_frags]),
+				XEN_NETIF_RSP_ERROR);
 	}
 	/* The head too, if necessary. */
 	if (start)
@@ -1025,8 +1164,10 @@ static int xen_netbk_tx_check_gop(struct xen_netbk *netbk,
 	struct gnttab_copy *gop = *gopp;
 	u16 pending_idx = *((u16 *)skb->data);
 	struct skb_shared_info *shinfo = skb_shinfo(skb);
+	struct pending_tx_info *tx_info;
 	int nr_frags = shinfo->nr_frags;
 	int i, err, start;
+	u16 peek; /* peek into next tx request */
 
 	/* Check status of header. */
 	err = gop->status;
@@ -1038,11 +1179,21 @@ static int xen_netbk_tx_check_gop(struct xen_netbk *netbk,
 
 	for (i = start; i < nr_frags; i++) {
 		int j, newerr;
+		pending_ring_idx_t head;
 
 		pending_idx = frag_get_pending_idx(&shinfo->frags[i]);
+		tx_info = &netbk->pending_tx_info[pending_idx];
+		head = tx_info->head;
 
 		/* Check error status: if okay then remember grant handle. */
-		newerr = (++gop)->status;
+		do {
+			newerr = (++gop)->status;
+			if (newerr)
+				break;
+			peek = netbk->pending_ring[pending_index(++head)];
+		} while (netbk->pending_tx_info[peek].head
+			 == INVALID_PENDING_RING_IDX);
+
 		if (likely(!newerr)) {
 			/* Had a previous error? Invalidate this fragment. */
 			if (unlikely(err))
@@ -1267,11 +1418,12 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 	struct sk_buff *skb;
 	int ret;
 
-	while (((nr_pending_reqs(netbk) + MAX_SKB_FRAGS) < MAX_PENDING_REQS) &&
+	while ((nr_pending_reqs(netbk) + XEN_NETIF_NR_SLOTS_MIN
+		 < MAX_PENDING_REQS) &&
 		!list_empty(&netbk->net_schedule_list)) {
 		struct xenvif *vif;
 		struct xen_netif_tx_request txreq;
-		struct xen_netif_tx_request txfrags[MAX_SKB_FRAGS];
+		struct xen_netif_tx_request txfrags[max_skb_slots];
 		struct page *page;
 		struct xen_netif_extra_info extras[XEN_NETIF_EXTRA_TYPE_MAX-1];
 		u16 pending_idx;
@@ -1332,7 +1484,8 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 				continue;
 		}
 
-		ret = netbk_count_requests(vif, &txreq, txfrags, work_to_do);
+		ret = netbk_count_requests(vif, &txreq, idx,
+					   txfrags, work_to_do);
 		if (unlikely(ret < 0))
 			continue;
 
@@ -1359,7 +1512,7 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 		pending_idx = netbk->pending_ring[index];
 
 		data_len = (txreq.size > PKT_PROT_LEN &&
-			    ret < MAX_SKB_FRAGS) ?
+			    ret < XEN_NETIF_NR_SLOTS_MIN) ?
 			PKT_PROT_LEN : txreq.size;
 
 		skb = alloc_skb(data_len + NET_SKB_PAD + NET_IP_ALIGN,
@@ -1409,6 +1562,7 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
 		memcpy(&netbk->pending_tx_info[pending_idx].req,
 		       &txreq, sizeof(txreq));
 		netbk->pending_tx_info[pending_idx].vif = vif;
+		netbk->pending_tx_info[pending_idx].head = index;
 		*((u16 *)skb->data) = pending_idx;
 
 		__skb_put(skb, data_len);
@@ -1539,7 +1693,10 @@ static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx,
 {
 	struct xenvif *vif;
 	struct pending_tx_info *pending_tx_info;
-	pending_ring_idx_t index;
+	pending_ring_idx_t head;
+	u16 peek; /* peek into next tx request */
+
+	BUG_ON(netbk->mmap_pages[pending_idx] == (void *)(~0UL));
 
 	/* Already complete? */
 	if (netbk->mmap_pages[pending_idx] == NULL)
@@ -1548,13 +1705,34 @@ static void xen_netbk_idx_release(struct xen_netbk *netbk, u16 pending_idx,
 	pending_tx_info = &netbk->pending_tx_info[pending_idx];
 
 	vif = pending_tx_info->vif;
+	head = pending_tx_info->head;
 
-	make_tx_response(vif, &pending_tx_info->req, status);
+	BUG_ON(head == INVALID_PENDING_RING_IDX);
+	BUG_ON(netbk->pending_ring[pending_index(head)] != pending_idx);
 
-	index = pending_index(netbk->pending_prod++);
-	netbk->pending_ring[index] = pending_idx;
+	do {
+		pending_ring_idx_t index;
+		pending_ring_idx_t idx = pending_index(head);
+		u16 info_idx = netbk->pending_ring[idx];
 
-	xenvif_put(vif);
+		pending_tx_info = &netbk->pending_tx_info[info_idx];
+		make_tx_response(vif, &pending_tx_info->req, status);
+
+		/* Setting any number other than
+		 * INVALID_PENDING_RING_IDX indicates this slot is
+		 * starting a new packet / ending a previous packet.
+		 */
+		pending_tx_info->head = 0;
+
+		index = pending_index(netbk->pending_prod++);
+		netbk->pending_ring[index] = netbk->pending_ring[info_idx];
+
+		xenvif_put(vif);
+
+		peek = netbk->pending_ring[pending_index(++head)];
+
+	} while (netbk->pending_tx_info[peek].head
+		 == INVALID_PENDING_RING_IDX);
 
 	netbk->mmap_pages[pending_idx]->mapping = 0;
 	put_page(netbk->mmap_pages[pending_idx]);
@@ -1613,7 +1791,8 @@ static inline int rx_work_todo(struct xen_netbk *netbk)
 static inline int tx_work_todo(struct xen_netbk *netbk)
 {
 
-	if (((nr_pending_reqs(netbk) + MAX_SKB_FRAGS) < MAX_PENDING_REQS) &&
+	if (((nr_pending_reqs(netbk) + XEN_NETIF_NR_SLOTS_MIN)
+	     < MAX_PENDING_REQS) &&
 			!list_empty(&netbk->net_schedule_list))
 		return 1;
 
diff --git a/include/xen/interface/io/netif.h b/include/xen/interface/io/netif.h
index 9dfc120..e829a09 100644
--- a/include/xen/interface/io/netif.h
+++ b/include/xen/interface/io/netif.h
@@ -13,6 +13,24 @@
 #include <xen/interface/grant_table.h>
 
 /*
+ * Older implementation of Xen network frontend / backend has an
+ * implicit dependency on the MAX_SKB_FRAGS as the maximum number of
+ * ring slots a skb can use. Netfront / netback may not work as
+ * expected when frontend and backend have different MAX_SKB_FRAGS.
+ *
+ * A better approach is to add mechanism for netfront / netback to
+ * negotiate this value. However we cannot fix all possible
+ * frontends, so we need to define a value which states the minimum
+ * slots backend must support.
+ *
+ * The minimum value derives from older Linux kernel's MAX_SKB_FRAGS
+ * (18), which is proved to work with most frontends. Any new backend
+ * which doesn't negotiate with frontend should expect frontend to
+ * send a valid packet using slots up to this value.
+ */
+#define XEN_NETIF_NR_SLOTS_MIN 18
+
+/*
  * Notifications after enqueuing any type of message should be conditional on
  * the appropriate req_event or rsp_event field in the shared ring.
  * If the client sends notification for rx requests then it should specify
-- 
1.7.10.4

Re: [PATCH V4 6/7] xen-netback: coalesce slots in TX path and fix regressions

[Ian Campbell]

On Fri, 2013-04-12 at 15:24 +0100, Wei Liu wrote:
> +/*
> + * This is the maximum slots a skb can have. If a guest sends a skb
> + * which exceeds this limit it is considered malicious.
> + */
> +#define MAX_SKB_SLOTS_DEFAULT 20
> +static unsigned int max_skb_slots = MAX_SKB_SLOTS_DEFAULT;
> +
> +static int max_skb_slots_set(const char *val, const struct kernel_param *kp)
> +{
> +       int ret;
> +       unsigned int param = 0;
> +
> +       ret = kstrtouint(val, 10, &param);
> +
> +       if (ret < 0 || param < XEN_NETIF_NR_SLOTS_MIN)
> +               return -EINVAL;
> +
> +       max_skb_slots = param;
> +
> +       return 0;
> +}
> +
> +static __moduleparam_const struct kernel_param_ops max_skb_slots_param_ops = {
> +       .set = max_skb_slots_set,
> +       .get = param_get_uint,
> +};
> +
> +module_param_cb(max_skb_slots, &max_skb_slots_param_ops,
> +               &max_skb_slots, 0444);

Is all this infrastructure instead of module_param_int just so we can
check XEN_NETIF_NR_SLOTS_MIN? I'm inclined to suggest that if an admin
wants to set a smaller slot limit then they get to keep the pieces.

Or if you really want to check it then you could check+log/reject in the
module init function.

> +
> +typedef unsigned int pending_ring_idx_t;
> +#define INVALID_PENDING_RING_IDX (~0U)
> +
>  struct pending_tx_info {
> -       struct xen_netif_tx_request req;
> +       struct xen_netif_tx_request req; /* coalesced tx request  */
>         struct xenvif *vif;
> +       pending_ring_idx_t head; /* head != INVALID_PENDING_RING_IDX
> +                                 * if it is head of one or more tx
> +                                 * reqs
> +                                 */
>  };
> -typedef unsigned int pending_ring_idx_t;
> 
>  struct netbk_rx_meta {
>         int id;
> @@ -102,7 +138,11 @@ struct xen_netbk {
>         atomic_t netfront_count;
> 
>         struct pending_tx_info pending_tx_info[MAX_PENDING_REQS];
> -       struct gnttab_copy tx_copy_ops[MAX_PENDING_REQS];
> +       /* Coalescing tx requests before copying makes number of grant
> +        * copy ops greater of equal to number of slots required. In
                              ^or

> +        * worst case a tx request consumes 2 gnttab_copy.

I'm happy with this as an upper bound but can it be made smaller?

For example there are at most MAX_PENDING_REQS on the ring, but we are
filling MAX_SKB_FRAGS with that data, therefore only MAX_SKB_FRAGS (-1?)
or those requests can cross a frag boundary and therefore the actual max
is MAX_PENDING_REQS+MAX_SKB_FRAGS.

Is that logic right? Perhaps need to account for data going into the
head too with another +N?

> +        */
> +       struct gnttab_copy tx_copy_ops[2*MAX_PENDING_REQS];
> 
>         u16 pending_ring[MAX_PENDING_REQS];
> 
[...]

> 
> -               memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + frags),
> +               /* Xen network protocol had implicit dependency on
> +                * MAX_SKB_FRAGS. XEN_NETIF_NR_SLOTS_MIN is set to the
> +                * historical MAX_SKB_FRAGS value 18 to honor the same
> +                * behavior as before. Any packet using more than 18
> +                * slots but less than max_skb_slots slots is dropped
> +                */

It seems a bit odd not to accept such a thing if the local network stack
can cope with it but I suppose the intention here is to maintain the
historical status quo to reduce the problem space when we imminently
implement proper negotiation between front- and backend about the number
of slots they can handle?

> +               if (!drop_err && slots >= XEN_NETIF_NR_SLOTS_MIN) {
> +                       if (net_ratelimit())
> +                               netdev_dbg(vif->dev,
> +                                          "Too many slots (%d), dropping packet\n",
> +                                          slots);

Could log the limits here?

> +                       drop_err = -E2BIG;
> +               }
> +
> +               memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + slots),

> @@ -1038,11 +1179,21 @@ static int xen_netbk_tx_check_gop(struct xen_netbk *netbk,
> 
>         for (i = start; i < nr_frags; i++) {
>                 int j, newerr;
> +               pending_ring_idx_t head;
> 
>                 pending_idx = frag_get_pending_idx(&shinfo->frags[i]);
> +               tx_info = &netbk->pending_tx_info[pending_idx];
> +               head = tx_info->head;
> 
>                 /* Check error status: if okay then remember grant handle. */
> -               newerr = (++gop)->status;
> +               do {
> +                       newerr = (++gop)->status;
> +                       if (newerr)
> +                               break;
> +                       peek = netbk->pending_ring[pending_index(++head)];
> +               } while (netbk->pending_tx_info[peek].head
> +                        == INVALID_PENDING_RING_IDX);

The 80 column limit is a soft one (and I think its greater nowadays
anyhow) and in cases like this the "cure" is worse than the disease, at
least in IMHO...

You are using INVALID_PENDING_RING_IDX as an indication of further
chaining, so the naming is a little counter intuitive. I can't think of
a name I like (something with "continuation" in it?) but perhaps a
helper function pending_tx_is_head(netbk, peek) or something would make
it read more clearly?

> +
>                 if (likely(!newerr)) {
>                         /* Had a previous error? Invalidate this fragment. */
>                         if (unlikely(err))

Re: [PATCH V4 6/7] xen-netback: coalesce slots in TX path and fix regressions

[Wei Liu]

On Fri, Apr 12, 2013 at 04:35:44PM +0100, Ian Campbell wrote:
[...]
> > +module_param_cb(max_skb_slots, &max_skb_slots_param_ops,
> > +               &max_skb_slots, 0444);
> 
> Is all this infrastructure instead of module_param_int just so we can
> check XEN_NETIF_NR_SLOTS_MIN? I'm inclined to suggest that if an admin
> wants to set a smaller slot limit then they get to keep the pieces.
> 
> Or if you really want to check it then you could check+log/reject in the
> module init function.
> 

I will go for the latter one. :-)

> > 
[...]
> >         struct pending_tx_info pending_tx_info[MAX_PENDING_REQS];
> > -       struct gnttab_copy tx_copy_ops[MAX_PENDING_REQS];
> > +       /* Coalescing tx requests before copying makes number of grant
> > +        * copy ops greater of equal to number of slots required. In
>                               ^or
> 
> > +        * worst case a tx request consumes 2 gnttab_copy.
> 
> I'm happy with this as an upper bound but can it be made smaller?
> 
> For example there are at most MAX_PENDING_REQS on the ring, but we are
> filling MAX_SKB_FRAGS with that data, therefore only MAX_SKB_FRAGS (-1?)
> or those requests can cross a frag boundary and therefore the actual max
> is MAX_PENDING_REQS+MAX_SKB_FRAGS.
> 
> Is that logic right? Perhaps need to account for data going into the
> head too with another +N?
> 

I'm afraid this is not the case. Vif has a ring of size
MAX_PENDING_REQS, but that ring might contain multiple skbs, so the
statement "we are filling MAX_SKB_FRAGS with that data" doesn't stand.

> > +        */
> > +       struct gnttab_copy tx_copy_ops[2*MAX_PENDING_REQS];
> > 
> >         u16 pending_ring[MAX_PENDING_REQS];
> > 
> [...]
> 
> > 
> > -               memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + frags),
> > +               /* Xen network protocol had implicit dependency on
> > +                * MAX_SKB_FRAGS. XEN_NETIF_NR_SLOTS_MIN is set to the
> > +                * historical MAX_SKB_FRAGS value 18 to honor the same
> > +                * behavior as before. Any packet using more than 18
> > +                * slots but less than max_skb_slots slots is dropped
> > +                */
> 
> It seems a bit odd not to accept such a thing if the local network stack
> can cope with it but I suppose the intention here is to maintain the
> historical status quo to reduce the problem space when we imminently
> implement proper negotiation between front- and backend about the number
> of slots they can handle?
> 

Yes, this behavior will be altered once we have mechanism to negotiate.


Wei.

[PATCH V4 7/7] xen-netback: don't disconnect frontend when seeing oversize packet

[Wei Liu]

Some frontend drivers are sending packets > 64 KiB in length. This length
overflows the length field in the first slot making the following slots have
an invalid length.

Turn this error back into a non-fatal error by dropping the packet. To avoid
having the following slots having fatal errors, consume all slots in the
packet.

This does not reopen the security hole in XSA-39 as if the packet as an
invalid number of slots it will still hit fatal error case.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
---
 drivers/net/xen-netback/netback.c |   22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 00ae841..e21c15e 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -993,12 +993,22 @@ static int netbk_count_requests(struct xenvif *vif,
 
 		memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + slots),
 		       sizeof(*txp));
-		if (txp->size > first->size) {
-			netdev_err(vif->dev,
-				   "Invalid tx request, slot size %u > remaining size %u\n",
-				   txp->size, first->size);
-			netbk_fatal_tx_err(vif);
-			return -EIO;
+
+		/* If the guest submitted a frame >= 64 KiB then
+		 * first->size overflowed and following slots will
+		 * appear to be larger than the frame.
+		 *
+		 * This cannot be fatal error as there are buggy
+		 * frontends that do this.
+		 *
+		 * Consume all slots and drop the packet.
+		 */
+		if (!drop_err && txp->size > first->size) {
+			if (net_ratelimit())
+				netdev_dbg(vif->dev,
+					   "Invalid tx request, slot size %u > remaining size %u\n",
+					   txp->size, first->size);
+			drop_err = -EIO;
 		}
 
 		first->size -= txp->size;
-- 
1.7.10.4

Re: [PATCH V4 7/7] xen-netback: don't disconnect frontend when seeing oversize packet

[Ian Campbell]

On Fri, 2013-04-12 at 15:24 +0100, Wei Liu wrote:
> Some frontend drivers are sending packets > 64 KiB in length. This length
> overflows the length field in the first slot making the following slots have
> an invalid length.
> 
> Turn this error back into a non-fatal error by dropping the packet. To avoid
> having the following slots having fatal errors, consume all slots in the
> packet.
> 
> This does not reopen the security hole in XSA-39 as if the packet as an
> invalid number of slots it will still hit fatal error case.
> 
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> Signed-off-by: Wei Liu <wei.liu2@citrix.com>

Acked-by: Ian Campbell <ian.campbell@citrix.com>

Re: [PATCH V4 7/7] xen-netback: don't disconnect frontend when seeing oversize packet

[William Dauchy]

On Fri, Apr 12, 2013 at 4:24 PM, Wei Liu <wei.liu2@citrix.com> wrote:
> Some frontend drivers are sending packets > 64 KiB in length. This length
> overflows the length field in the first slot making the following slots have
> an invalid length.
>
> Turn this error back into a non-fatal error by dropping the packet. To avoid
> having the following slots having fatal errors, consume all slots in the
> packet.
>
> This does not reopen the security hole in XSA-39 as if the packet as an
> invalid number of slots it will still hit fatal error case.
>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> Signed-off-by: Wei Liu <wei.liu2@citrix.com>

Maybe this should be tagged for stable? Maybe part of patch 6/7 as
well. I had to remove the part which was disabling the device because
of issues encountered in stable tree.

--
William

Re: [PATCH V4 7/7] xen-netback: don't disconnect frontend when seeing oversize packet

[Ian Campbell]

On Fri, 2013-04-12 at 18:17 +0100, William Dauchy wrote:
> On Fri, Apr 12, 2013 at 4:24 PM, Wei Liu <wei.liu2@citrix.com> wrote:
> > Some frontend drivers are sending packets > 64 KiB in length. This length
> > overflows the length field in the first slot making the following slots have
> > an invalid length.
> >
> > Turn this error back into a non-fatal error by dropping the packet. To avoid
> > having the following slots having fatal errors, consume all slots in the
> > packet.
> >
> > This does not reopen the security hole in XSA-39 as if the packet as an
> > invalid number of slots it will still hit fatal error case.
> >
> > Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> > Signed-off-by: Wei Liu <wei.liu2@citrix.com>
> 
> Maybe this should be tagged for stable? Maybe part of patch 6/7 as
> well. I had to remove the part which was disabling the device because
> of issues encountered in stable tree.

AFAICT the majority of this series (as well as perhaps some of Wei's
earlier fixes) should be candidates for any stable tree which received
the XSA-39 security fixes. Wei -- could you enumerate which patches are
required to fixup the XSA-39 regressions?

Ian.

Re: [PATCH V4 7/7] xen-netback: don't disconnect frontend when seeing oversize packet

[Wei Liu]

On Mon, Apr 15, 2013 at 10:03:25AM +0100, Ian Campbell wrote:
> On Fri, 2013-04-12 at 18:17 +0100, William Dauchy wrote:
> > On Fri, Apr 12, 2013 at 4:24 PM, Wei Liu <wei.liu2@citrix.com> wrote:
> > > Some frontend drivers are sending packets > 64 KiB in length. This length
> > > overflows the length field in the first slot making the following slots have
> > > an invalid length.
> > >
> > > Turn this error back into a non-fatal error by dropping the packet. To avoid
> > > having the following slots having fatal errors, consume all slots in the
> > > packet.
> > >
> > > This does not reopen the security hole in XSA-39 as if the packet as an
> > > invalid number of slots it will still hit fatal error case.
> > >
> > > Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> > > Signed-off-by: Wei Liu <wei.liu2@citrix.com>
> > 
> > Maybe this should be tagged for stable? Maybe part of patch 6/7 as
> > well. I had to remove the part which was disabling the device because
> > of issues encountered in stable tree.
> 
> AFAICT the majority of this series (as well as perhaps some of Wei's
> earlier fixes) should be candidates for any stable tree which received
> the XSA-39 security fixes. Wei -- could you enumerate which patches are
> required to fixup the XSA-39 regressions?
> 

Are mechinical fixes such as removing redudent variables / changing log
messages candidates for stable? 1-4 are such kind of fixes.

5-7 are the real meat. If 1-4 are not taken to stable, they will need
small adjustment to apply, which is just trivial.


Wei.

> Ian.
> 

Re: [PATCH V4 7/7] xen-netback: don't disconnect frontend when seeing oversize packet

[Wei Liu]

On Mon, Apr 15, 2013 at 03:53:20PM +0100, Wei Liu wrote:
> 
> 5-7 are the real meat. If 1-4 are not taken to stable, they will need
> small adjustment to apply, which is just trivial.
> 

And just to be clear, 5 is not specific written for XSA-39 as it is a
fix for netfront and XSA-39 is fix to netback. However it should
go to stable as well.


Wei.

> 
> Wei.
> 
> > Ian.
> > 

Re: [PATCH V4 7/7] xen-netback: don't disconnect frontend when seeing oversize packet

[Ian Campbell]

On Mon, 2013-04-15 at 15:53 +0100, Wei Liu wrote:
> On Mon, Apr 15, 2013 at 10:03:25AM +0100, Ian Campbell wrote:
> > On Fri, 2013-04-12 at 18:17 +0100, William Dauchy wrote:
> > > On Fri, Apr 12, 2013 at 4:24 PM, Wei Liu <wei.liu2@citrix.com> wrote:
> > > > Some frontend drivers are sending packets > 64 KiB in length. This length
> > > > overflows the length field in the first slot making the following slots have
> > > > an invalid length.
> > > >
> > > > Turn this error back into a non-fatal error by dropping the packet. To avoid
> > > > having the following slots having fatal errors, consume all slots in the
> > > > packet.
> > > >
> > > > This does not reopen the security hole in XSA-39 as if the packet as an
> > > > invalid number of slots it will still hit fatal error case.
> > > >
> > > > Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> > > > Signed-off-by: Wei Liu <wei.liu2@citrix.com>
> > > 
> > > Maybe this should be tagged for stable? Maybe part of patch 6/7 as
> > > well. I had to remove the part which was disabling the device because
> > > of issues encountered in stable tree.
> > 
> > AFAICT the majority of this series (as well as perhaps some of Wei's
> > earlier fixes) should be candidates for any stable tree which received
> > the XSA-39 security fixes. Wei -- could you enumerate which patches are
> > required to fixup the XSA-39 regressions?
> > 
> 
> Are mechinical fixes such as removing redudent variables / changing log
> messages candidates for stable? 1-4 are such kind of fixes.

#4 looks like meat to me too?

My personal opinion is that it is better where possible to take
relatively simple and/or obvious precursors (renaming and such fit this
IMHO) than to risk making a mistake in the backport.

> 5-7 are the real meat. If 1-4 are not taken to stable, they will need
> small adjustment to apply, which is just trivial.
> 
> 
> Wei.
> 
> > Ian.
> > 

Re: [PATCH V4 7/7] xen-netback: don't disconnect frontend when seeing oversize packet

[Wei Liu]

On Mon, Apr 15, 2013 at 04:24:49PM +0100, Ian Campbell wrote:
> On Mon, 2013-04-15 at 15:53 +0100, Wei Liu wrote:
> > On Mon, Apr 15, 2013 at 10:03:25AM +0100, Ian Campbell wrote:
> > > On Fri, 2013-04-12 at 18:17 +0100, William Dauchy wrote:
> > > > On Fri, Apr 12, 2013 at 4:24 PM, Wei Liu <wei.liu2@citrix.com> wrote:
> > > > > Some frontend drivers are sending packets > 64 KiB in length. This length
> > > > > overflows the length field in the first slot making the following slots have
> > > > > an invalid length.
> > > > >
> > > > > Turn this error back into a non-fatal error by dropping the packet. To avoid
> > > > > having the following slots having fatal errors, consume all slots in the
> > > > > packet.
> > > > >
> > > > > This does not reopen the security hole in XSA-39 as if the packet as an
> > > > > invalid number of slots it will still hit fatal error case.
> > > > >
> > > > > Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> > > > > Signed-off-by: Wei Liu <wei.liu2@citrix.com>
> > > > 
> > > > Maybe this should be tagged for stable? Maybe part of patch 6/7 as
> > > > well. I had to remove the part which was disabling the device because
> > > > of issues encountered in stable tree.
> > > 
> > > AFAICT the majority of this series (as well as perhaps some of Wei's
> > > earlier fixes) should be candidates for any stable tree which received
> > > the XSA-39 security fixes. Wei -- could you enumerate which patches are
> > > required to fixup the XSA-39 regressions?
> > > 
> > 
> > Are mechinical fixes such as removing redudent variables / changing log
> > messages candidates for stable? 1-4 are such kind of fixes.
> 
> #4 looks like meat to me too?
> 

Not really. DaveM applied first 3 and later I discoverd there was a log
message which should have been changed in 2. So I wrote a incremental
patch on top of 2 to fix that.

> My personal opinion is that it is better where possible to take
> relatively simple and/or obvious precursors (renaming and such fit this
> IMHO) than to risk making a mistake in the backport.
> 

OK, then the whole series is candidate for stable.


Wei.

Re: [PATCH V4 7/7] xen-netback: don't disconnect frontend when seeing oversize packet

[Ian Campbell]

> > > Are mechinical fixes such as removing redudent variables / changing log
> > > messages candidates for stable? 1-4 are such kind of fixes.
> > 
> > #4 looks like meat to me too?
> > 
> 
> Not really. DaveM applied first 3 and later I discoverd there was a log
> message which should have been changed in 2. So I wrote a incremental
> patch on top of 2 to fix that.

Oops, I think I read "V4 7/7" as 4/7...

> 
> > My personal opinion is that it is better where possible to take
> > relatively simple and/or obvious precursors (renaming and such fit this
> > IMHO) than to risk making a mistake in the backport.
> > 
> 
> OK, then the whole series is candidate for stable.

Once things go in can you enumerate the actual commit numbers please?

Ian.

Re: [PATCH V4 7/7] xen-netback: don't disconnect frontend when seeing oversize packet

[Wei Liu]

On Mon, Apr 15, 2013 at 04:35:04PM +0100, Ian Campbell wrote:
> 
> > > > Are mechinical fixes such as removing redudent variables / changing log
> > > > messages candidates for stable? 1-4 are such kind of fixes.
> > > 
> > > #4 looks like meat to me too?
> > > 
> > 
> > Not really. DaveM applied first 3 and later I discoverd there was a log
> > message which should have been changed in 2. So I wrote a incremental
> > patch on top of 2 to fix that.
> 
> Oops, I think I read "V4 7/7" as 4/7...
> 
> > 
> > > My personal opinion is that it is better where possible to take
> > > relatively simple and/or obvious precursors (renaming and such fit this
> > > IMHO) than to risk making a mistake in the backport.
> > > 
> > 
> > OK, then the whole series is candidate for stable.
> 
> Once things go in can you enumerate the actual commit numbers please?
> 

Sure.


Wei.

> Ian.
> 

Re: [PATCH V4 7/7] xen-netback: don't disconnect frontend when seeing oversize packet

[David Miller]

From: Wei Liu <wei.liu2@citrix.com>
Date: Mon, 15 Apr 2013 16:30:38 +0100

> On Mon, Apr 15, 2013 at 04:24:49PM +0100, Ian Campbell wrote:
>> On Mon, 2013-04-15 at 15:53 +0100, Wei Liu wrote:
>> > On Mon, Apr 15, 2013 at 10:03:25AM +0100, Ian Campbell wrote:
>> > > On Fri, 2013-04-12 at 18:17 +0100, William Dauchy wrote:
>> > > > On Fri, Apr 12, 2013 at 4:24 PM, Wei Liu <wei.liu2@citrix.com> wrote:
>> > > > > Some frontend drivers are sending packets > 64 KiB in length. This length
>> > > > > overflows the length field in the first slot making the following slots have
>> > > > > an invalid length.
>> > > > >
>> > > > > Turn this error back into a non-fatal error by dropping the packet. To avoid
>> > > > > having the following slots having fatal errors, consume all slots in the
>> > > > > packet.
>> > > > >
>> > > > > This does not reopen the security hole in XSA-39 as if the packet as an
>> > > > > invalid number of slots it will still hit fatal error case.
>> > > > >
>> > > > > Signed-off-by: David Vrabel <david.vrabel@citrix.com>
>> > > > > Signed-off-by: Wei Liu <wei.liu2@citrix.com>
>> > > > 
>> > > > Maybe this should be tagged for stable? Maybe part of patch 6/7 as
>> > > > well. I had to remove the part which was disabling the device because
>> > > > of issues encountered in stable tree.
>> > > 
>> > > AFAICT the majority of this series (as well as perhaps some of Wei's
>> > > earlier fixes) should be candidates for any stable tree which received
>> > > the XSA-39 security fixes. Wei -- could you enumerate which patches are
>> > > required to fixup the XSA-39 regressions?
>> > > 
>> > 
>> > Are mechinical fixes such as removing redudent variables / changing log
>> > messages candidates for stable? 1-4 are such kind of fixes.
>> 
>> #4 looks like meat to me too?
>> 
> 
> Not really. DaveM applied first 3 and later I discoverd there was a log
> message which should have been changed in 2. So I wrote a incremental
> patch on top of 2 to fix that.

Please don't do this, it is so confusing.

When I've applied some of your patches, don't repost them, only post the
new patches which are not yet in my tree.

All development and patches occurs relative to my tree, so by reposting
patches already applied you make for confusion and more work on my part.