xen-gntdev: Fix incorrect use of zero handle

The handle with numeric value 0 is a valid map handle, so it cannot
be used to indicate that a page has not been mapped. Use -1 instead.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 16 insertions, 7 deletions

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 2a4733c621c0..cdc28dc8b5d9 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -126,6 +126,8 @@ static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count)
                 add->pages[i] = alloc_page(GFP_KERNEL | __GFP_HIGHMEM);
                 if (add->pages[i] == NULL)
                         goto err;
+                add->map_ops[i].handle = -1;
+                add->unmap_ops[i].handle = -1;
         }
 
         add->index = 0;
@@ -248,7 +250,7 @@ static int find_grant_ptes(pte_t *pte, pgtable_t token,
                           map->grants[pgnr].ref,
                           map->grants[pgnr].domid);
         gnttab_set_unmap_op(&map->unmap_ops[pgnr], pte_maddr, flags,
-                            0 /* handle */);
+                            -1 /* handle */);
         return 0;
 }
 
@@ -259,7 +261,7 @@ static int map_grant_pages(struct grant_map *map)
 
         if (!use_ptemod) {
                 /* Note: it could already be mapped */
-                if (map->map_ops[0].handle)
+                if (map->map_ops[0].handle != -1)
                         return 0;
                 for (i = 0; i < map->count; i++) {
                         addr = (phys_addr_t)
@@ -268,7 +270,7 @@ static int map_grant_pages(struct grant_map *map)
                                 map->grants[i].ref,
                                 map->grants[i].domid);
                         gnttab_set_unmap_op(&map->unmap_ops[i], addr,
-                                map->flags, 0 /* handle */);
+                                map->flags, -1 /* handle */);
                 }
         }
 
@@ -280,7 +282,11 @@ static int map_grant_pages(struct grant_map *map)
         for (i = 0; i < map->count; i++) {
                 if (map->map_ops[i].status)
                         err = -EINVAL;
-                map->unmap_ops[i].handle = map->map_ops[i].handle;
+                else {
+                        BUG_ON(map->map_ops[i].handle == -1);
+                        map->unmap_ops[i].handle = map->map_ops[i].handle;
+                        pr_debug("map handle=%d\n", map->map_ops[i].handle);
+                }
         }
         return err;
 }
@@ -313,7 +319,10 @@ static int __unmap_grant_pages(struct grant_map *map, int offset, int pages)
         for (i = 0; i < pages; i++) {
                 if (map->unmap_ops[offset+i].status)
                         err = -EINVAL;
-                map->unmap_ops[offset+i].handle = 0;
+                pr_debug("unmap handle=%d st=%d\n",
+                        map->unmap_ops[offset+i].handle,
+                        map->unmap_ops[offset+i].status);
+                map->unmap_ops[offset+i].handle = -1;
         }
         return err;
 }
@@ -328,13 +337,13 @@ static int unmap_grant_pages(struct grant_map *map, int offset, int pages)
          * already unmapped some of the grants. Only unmap valid ranges.
          */
         while (pages && !err) {
-                while (pages && !map->unmap_ops[offset].handle) {
+                while (pages && map->unmap_ops[offset].handle == -1) {
                         offset++;
                         pages--;
                 }
                 range = 0;
                 while (range < pages) {
-                        if (!map->unmap_ops[offset+range].handle) {
+                        if (map->unmap_ops[offset+range].handle == -1) {
                                 range--;
                                 break;
                         }