Merge branch 'netback'

Ian Campbell says:

====================
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

Changes in v2:
 - Typo and block comment format fixes
 - Added stable Cc
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 88 insertions, 53 deletions

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 94b79c3338c4..9d7f1723dd8f 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 b7d41f8c338a..b8c5193bd420 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 f2d6b78d901d..2b9520c46e97 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);
@@ -879,7 +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);
@@ -888,6 +889,13 @@ 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 +909,22 @@ 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 +932,9 @@ 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);
@@ -966,7 +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;
@@ -988,6 +1000,17 @@ static struct gnttab_copy *xen_netbk_get_requests(struct xen_netbk *netbk,
         }
 
         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);
+        }
+        /* 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,
@@ -996,30 +1019,20 @@ 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]);
 
@@ -1028,16 +1041,12 @@ 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)
@@ -1045,10 +1054,10 @@ 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. */
@@ -1082,7 +1091,7 @@ 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);
         }
 }
 
@@ -1095,7 +1104,8 @@ 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 +1114,9 @@ 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 +1132,15 @@ 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 +1277,25 @@ 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 +1323,14 @@ 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 +1342,11 @@ 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 +1374,8 @@ 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;
                         }
                 }
@@ -1448,7 +1474,7 @@ 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)
@@ -1500,7 +1526,8 @@ 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;
@@ -1514,7 +1541,7 @@ 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;