[PULL,27/32] qcow2-refcount: check_refcounts_l2(): check l2_bitmap

Commit Message

Hanna Czenczek Sept. 15, 2021, 5:53 p.m. UTC

From: Vladimir Sementsov-Ogievskiy <[e-mail]>

Check subcluster bitmap of the l2 entry for different types of
clusters:

 - for compressed it must be zero
 - for allocated check consistency of two parts of the bitmap
 - for unallocated all subclusters should be unallocated
   (or zero-plain)

Signed-off-by: Vladimir Sementsov-Ogievskiy <[e-mail]>
Tested-by: Kirill Tkhai <[e-mail]>
Message-Id: <[e-mail]>
Reviewed-by: Eric Blake <[e-mail]>
Reviewed-by: Hanna Reitz <[e-mail]>
Signed-off-by: Hanna Reitz <[e-mail]>
---
 block/qcow2-refcount.c | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

Patch

diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index f48c5e1b5d..9a5ae3cac4 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1661,7 +1661,7 @@  static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
                               int flags, BdrvCheckMode fix, bool active)
 {
     BDRVQcow2State *s = bs->opaque;
-    uint64_t l2_entry;
+    uint64_t l2_entry, l2_bitmap;
     uint64_t next_contiguous_offset = 0;
     int i, ret;
     size_t l2_size_bytes = s->l2_size * l2_entry_size(s);
@@ -1681,6 +1681,7 @@  static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
         uint64_t coffset;
         int csize;
         l2_entry = get_l2_entry(s, l2_table, i);
+        l2_bitmap = get_l2_bitmap(s, l2_table, i);
 
         switch (qcow2_get_cluster_type(bs, l2_entry)) {
         case QCOW2_CLUSTER_COMPRESSED:
@@ -1700,6 +1701,14 @@  static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
                 break;
             }
 
+            if (l2_bitmap) {
+                fprintf(stderr, "ERROR compressed cluster %d with non-zero "
+                        "subcluster allocation bitmap, entry=0x%" PRIx64 "\n",
+                        i, l2_entry);
+                res->corruptions++;
+                break;
+            }
+
             /* Mark cluster as used */
             qcow2_parse_compressed_l2_entry(bs, l2_entry, &coffset, &csize);
             ret = qcow2_inc_refcounts_imrt(
@@ -1727,13 +1736,19 @@  static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
         {
             uint64_t offset = l2_entry & L2E_OFFSET_MASK;
 
+            if ((l2_bitmap >> 32) & l2_bitmap) {
+                res->corruptions++;
+                fprintf(stderr, "ERROR offset=%" PRIx64 ": Allocated "
+                        "cluster has corrupted subcluster allocation bitmap\n",
+                        offset);
+            }
+
             /* Correct offsets are cluster aligned */
             if (offset_into_cluster(s, offset)) {
                 bool contains_data;
                 res->corruptions++;
 
                 if (has_subclusters(s)) {
-                    uint64_t l2_bitmap = get_l2_bitmap(s, l2_table, i);
                     contains_data = (l2_bitmap & QCOW_L2_BITMAP_ALL_ALLOC);
                 } else {
                     contains_data = !(l2_entry & QCOW_OFLAG_ZERO);
@@ -1799,7 +1814,16 @@  static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
         }
 
         case QCOW2_CLUSTER_ZERO_PLAIN:
+            /* Impossible when image has subclusters */
+            assert(!l2_bitmap);
+            break;
+
         case QCOW2_CLUSTER_UNALLOCATED:
+            if (l2_bitmap & QCOW_L2_BITMAP_ALL_ALLOC) {
+                res->corruptions++;
+                fprintf(stderr, "ERROR: Unallocated "
+                        "cluster has non-zero subcluster allocation map\n");
+            }
             break;
 
         default: