[Qemu-devel] [PATCH 13/22] qcow2-bitmap: check constraints

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

Check bitmap header constraints as specified in docs/specs/qcow2.txt

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/qcow2-bitmap.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
index 8cf40f0..1c3abea 100644
--- a/block/qcow2-bitmap.c
+++ b/block/qcow2-bitmap.c
@@ -154,6 +154,34 @@ static inline void bitmap_directory_to_be(uint8_t *dir, size_t size)
     }
 }
 
+static int check_constraints(BlockDriverState *bs, Qcow2BitmapDirEntry *h)
+{
+    BDRVQcow2State *s = bs->opaque;
+    uint64_t phys_bitmap_bytes =
+        (uint64_t)h->bitmap_table_size * s->cluster_size;
+    uint64_t max_virtual_bits = (phys_bitmap_bytes * 8) << h->granularity_bits;
+    int64_t nb_sectors = bdrv_nb_sectors(bs);
+
+    if (nb_sectors < 0) {
+        return nb_sectors;
+    }
+
+    int fail =
+            ((h->bitmap_table_size == 0) != (h->bitmap_table_offset == 0)) ||
+            (h->bitmap_table_offset % s->cluster_size) ||
+            (h->bitmap_table_size > BME_MAX_TABLE_SIZE) ||
+            (phys_bitmap_bytes > BME_MAX_PHYS_SIZE) ||
+            (h->bitmap_table_offset != 0 &&
+                (nb_sectors << BDRV_SECTOR_BITS) > max_virtual_bits) ||
+            (h->granularity_bits > BME_MAX_GRANULARITY_BITS) ||
+            (h->granularity_bits < BME_MIN_GRANULARITY_BITS) ||
+            (h->flags & BME_RESERVED_FLAGS) ||
+            (h->name_size > BME_MAX_NAME_SIZE) ||
+            (h->type != BT_DIRTY_TRACKING_BITMAP);
+
+    return fail ? -EINVAL : 0;
+}
+
 static void clear_bitmap_table(BlockDriverState *bs, uint64_t *bitmap_table,
                                uint32_t bitmap_table_size)
 {
@@ -372,6 +400,12 @@ static uint8_t *directory_read(BlockDriverState *bs,
                        bdrv_get_device_or_node_name(bs));
             goto fail;
         }
+
+        ret = check_constraints(bs, e);
+        if (ret < 0) {
+            error_setg(errp, "Bitmap doesn't satisfy the constraints.");
+            goto fail;
+        }
     }
 
     assert((uint8_t *)e == dir_end);
@@ -713,6 +747,11 @@ static int store_bitmap(BlockDriverState *bs,
     entry->extra_data_size = 0;
     memcpy(entry + 1, bm_name, entry->name_size);
 
+    ret = check_constraints(bs, entry);
+    if (ret < 0) {
+        goto fail;
+    }
+
     return 0;
 
 fail:
-- 
1.8.3.1