1 files changed, 17 insertions, 10 deletions

diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index d36fcc0f2715..e65d6cbf2419 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -126,9 +126,13 @@ struct device
         /* The linked-list pointer. */
         struct device *next;
 
-        /* The this device's descriptor, as mapped into the Guest. */
+        /* The device's descriptor, as mapped into the Guest. */
         struct lguest_device_desc *desc;
 
+        /* We can't trust desc values once Guest has booted: we use these. */
+        unsigned int feature_len;
+        unsigned int num_vq;
+
         /* The name of this device, for --verbose. */
         const char *name;
 
@@ -245,7 +249,7 @@ static void iov_consume(struct iovec iov[], unsigned num_iov, unsigned len)
 static u8 *get_feature_bits(struct device *dev)
 {
         return (u8 *)(dev->desc + 1)
-                + dev->desc->num_vq * sizeof(struct lguest_vqconfig);
+                + dev->num_vq * sizeof(struct lguest_vqconfig);
 }
 
 /*L:100 The Launcher code itself takes us out into userspace, that scary place
@@ -979,8 +983,8 @@ static void update_device_status(struct device *dev)
                 verbose("Resetting device %s\n", dev->name);
 
                 /* Clear any features they've acked. */
-                memset(get_feature_bits(dev) + dev->desc->feature_len, 0,
-                       dev->desc->feature_len);
+                memset(get_feature_bits(dev) + dev->feature_len, 0,
+                       dev->feature_len);
 
                 /* Zero out the virtqueues. */
                 for (vq = dev->vq; vq; vq = vq->next) {
@@ -994,12 +998,12 @@ static void update_device_status(struct device *dev)
                 unsigned int i;
 
                 verbose("Device %s OK: offered", dev->name);
-                for (i = 0; i < dev->desc->feature_len; i++)
+                for (i = 0; i < dev->feature_len; i++)
                         verbose(" %02x", get_feature_bits(dev)[i]);
                 verbose(", accepted");
-                for (i = 0; i < dev->desc->feature_len; i++)
+                for (i = 0; i < dev->feature_len; i++)
                         verbose(" %02x", get_feature_bits(dev)
-                                [dev->desc->feature_len+i]);
+                                [dev->feature_len+i]);
 
                 if (dev->ready)
                         dev->ready(dev);
@@ -1129,8 +1133,8 @@ static void handle_input(int fd)
 static u8 *device_config(const struct device *dev)
 {
         return (void *)(dev->desc + 1)
-                + dev->desc->num_vq * sizeof(struct lguest_vqconfig)
-                + dev->desc->feature_len * 2;
+                + dev->num_vq * sizeof(struct lguest_vqconfig)
+                + dev->feature_len * 2;
 }
 
 /* This routine allocates a new "struct lguest_device_desc" from descriptor
@@ -1191,6 +1195,7 @@ static void add_virtqueue(struct device *dev, unsigned int num_descs,
          * yet, otherwise we'd be overwriting them. */
         assert(dev->desc->config_len == 0 && dev->desc->feature_len == 0);
         memcpy(device_config(dev), &vq->config, sizeof(vq->config));
+        dev->num_vq++;
         dev->desc->num_vq++;
 
         verbose("Virtqueue page %#lx\n", to_guest_phys(p));
@@ -1219,7 +1224,7 @@ static void add_feature(struct device *dev, unsigned bit)
         /* We can't extend the feature bits once we've added config bytes */
         if (dev->desc->feature_len <= bit / CHAR_BIT) {
                 assert(dev->desc->config_len == 0);
-                dev->desc->feature_len = (bit / CHAR_BIT) + 1;
+                dev->feature_len = dev->desc->feature_len = (bit/CHAR_BIT) + 1;
         }
 
         features[bit / CHAR_BIT] |= (1 << (bit % CHAR_BIT));
@@ -1259,6 +1264,8 @@ static struct device *new_device(const char *name, u16 type, int fd,
         dev->name = name;
         dev->vq = NULL;
         dev->ready = NULL;
+        dev->feature_len = 0;
+        dev->num_vq = 0;
 
         /* Append to device list.  Prepending to a single-linked list is
          * easier, but the user expects the devices to be arranged on the bus