[Xen-devel] [PATCH 1/2] xen-gntdev: Fix incorrect use of zero handle

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

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@xxxxxxxxxxxxx>
---
 drivers/xen/gntdev.c |   23 ++++++++++++++++-------
 1 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 2a4733c..cdc28dc 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;
                        }
-- 
1.7.3.4


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